[12] WATER-WALLED MICROFLUIDICS

 

Shai Maayani

 

Water-Walled Microfluidics

Liquids serve microcavity research ever since Ashkin’s studies on optical resonances in levitating droplets to recent optofluidic resonators. Droplets can provide optical quality factor (Q) in proximity to the limit restricted by water absorption and radiation loss. However, water micro-drops vaporize quickly due to their large area/volume ratio. Here we fabricate a water-air interface that almost entirely surrounds our device, allowing for >1,000,000 recirculations of light (finesse). We sustain the droplets for >16 hours using a nano-water-bridge that extends from the droplet to a practically-unlimited distant-reservoir that compensates for evaporation. Our device exhibits surface tension 8000-times stronger than gravity that self-stabilizes its shape to a degree sufficient to maintain critical coupling  as well as to resolve split modes. Our device has 98% of their surrounding walls made strictly of water-air interfaces with concave, convex or saddle geometries, suggesting an arbitrary-shape microfluidic technology with water-walls almost all-over.

 

 

 

[13] CAVITY OPTOCAPILLARY WITH WATER-WALLED RESONATORS

 

Shai Maayani¹

 

1 Technion; Technion

 

 

Cavity Optocapillary with Water-Walled Resonators

Droplets, particularly water, are abundant in nature and artificial systems. If only we could monitor droplet interfaces at sub-nanometer resolution, we could see that it behaves like a stormy sea. This phenomenon has widely been studied since 1908 and is of key importance in surface science. Here we use the optical mode of a mdroplet to probe its radius fluctuation. Doing so, we record Brownian droplet-vibrations at 100-kHz rates and 1 0.006 ångström amplitude, in agreement with natural-frequency calculation and equipartition theorem. A fall in the fluctuation spectrum is measured below cutoff at the drop’s lowest eigenfrequency. Our resonantly-enhanced measurement technique may impact the study of thermal-capillaries in droplets which are significant to coalescence and rupture processes, particularly with the most-common and important liquid – water.

 

 

 

 

[15] DROPLET’S ACOUSTICS

 

tal carmon¹, leopoldo martin¹, raphael dahan¹

 

1 Technion; Technion

 

 

Droplets represent a basic liquid structure that is contained by interfacial tension while bounded almost completely by free surfaces. Such droplets can host three types of resonances: optical-, capillary- and acoustical-ones. Contrary to their capillary resonances (Rayleigh, 1879) and to optical resonances (Ashkin, 1977), droplets’ acoustical resonances were rarely considered. The challenge lies in the fact that mdroplets’ acoustics requires modulating forces at MHz rates. Here we rely on optical forces (that can act sufficiently quickly) to experimentally excite acoustical resonances at 37 MHz that starts vibrating at an optical threshold of 68 mW. The optical modes that we are using as a mechanical exciter are circulating in the 40 mm drop with a 10⁸   quality-factor. Our results open an experimental access to the acoustical resonances of droplets, which were rarely considered, neither theoretically nor experimentally.

 

 

 

[47] STIMULATED EMISSION (STED) PULSED MICROSCOPE WITH SUPERCONTINUUM LASER SOURCE.

 

Eugene Brozgol¹

 

1 Bar Ilan; Bar Ilan

 

 

Stimulated Emission (STED) pulsed microscope with supercontinuum laser source.

Eugene Brozgol, Liat Altman, Yuval Garini

 

Abstract

Many biological structures have important characteristics at the nanometer scale. Due to the limitations of electronic and optical microscopy, these structures are poorly understood.

In our present work we focus on building a Stimulated Emission Depletion (STED) microscope, based on a pulsed, super continuum laser source.  Such a setup has unique characteristics, and will be utilized for studying the fine details of the telomere’s structure in eukaryotic nuclei. A telomere is a region of repetitive nucleotide sequences at each end of a chromatid, which protects the end of the chromosome from deterioration or from fusion with neighboring chromosomes. This study is interesting because telomere dysfunction is linked to genomic instability and tumorigenesis

Here we present the basics of the pulsed, continuum laser STED setup.

 

 

 

[49] MOLECULAR VIBRATION POLARITONS IN LOW-LOSS DIELECTRIC MICROCAVITIES IN THE MID-INFRARED

 

Merav Muallem¹, Alex Palatnik¹, Daniel Nessim¹, Yaakov Tischler¹

 

1 Bar-Ilan Institute of Nanotechnology and Advanced Materials; Bar-Ilan University

 

 

Microcavity devices exhibiting strong light-matter coupling in the mid-infrared spectral range offer the potential to explore exciting open physical questions pertaining to energy transfer between heat and light and can lead to a new generation of efficient wavelength tunable mid-infrared sources of coherent light based on polariton Bose-Einstein Condensation. Vibrational transitions of organic molecules, which often have strong absorption peaks in the infrared and considerably narrower linewidths than organic excitonic resonances, can generate polaritonic states in the mid-infrared spectral range using microcavity devices.

Here, narrow linewidth polaritonic resonances are exhibited in the mid-infrared by coupling the carbonyl stretch vibrational transition of a polymethyl methacrylate (PMMA) film to the photonic resonance of a low optical-loss mid-infrared microcavity, which consisted of two Ge/ZnS dielectric Bragg reflectors. Rabi-splitting of 14.3 meV is observed, with a 4.4 meV polariton linewidth at anti-crossing. The large Rabi-splitting relative to linewidth indicates efficient impedance-matching between the bare vibrational and photonic states.

Furthermore, polariton states from coupling a mixture of two vibration modes to the microcavity resonance are revealed using organic film composed from solid PMMA and liquid dimethylformamide (DMF). The solid and liquid components, both possess spectrally narrow carbonyl stretch peaks, resulting in three branches in the polariton dispersion relation. The upper branch (UB) is composed largely of the PMMA phonon and photon. The middle branch (MB) contains all three components, and the lower branch (LB) is mostly the DMF phonon mixed with the photon. Rabi splitting of 9.6 meV and 5.2 meV is found between the UB and the MB, and between the MB and LB, respectively. The sum of the Rabi splitting values, 14.8 meV, is similar to that of the PMMA cavity splitting.

Molecular-vibration polaritons incorporated in dielectric microcavities can be an enabling step towards realizing polariton optical switching, polariton condensation, and new hybrid coupled states of light and matter in both solid and liquid form, in the mid-infrared spectral range.

 

 

 

[57] INKJET PRINTING OF FLUORESCENT SEEDED NANORODS

 

Shira Halivni¹

 

1 Hebrew University of Jerusale; Physical Chemistry

 

 

Inkjet Printing of Fluorescent Seeded Nanorods

 

Shira Halivni, Shay Shemesh, Nir Waiskopf, Yelena Vinetsky, Shlomo Magdassi and Uri Banin

 

Institute of Chemistry and the Center for Nanoscience and Nanotechnology, the Hebrew University of Jerusalem, Jerusalem, 91904, Israel.

The use of fluorescent semiconductor nanocrystals for ink-jet printing applications is gaining momentum in the last few years. Their unique optical features that are characterized by wide absorption spectrum accompanied by a tunable, sharp and narrow emission spectrum, along with their optical and chemical stability, offer interesting advantages for their implementation in various technologies.

Although the use of fluorescent spherical semiconductor nanocrystals (quantum dots) is previously reported, there are no reports for the use of fluorescent nanorods (quantum rods) in ink applications, and especially in ink-jet inks. Fluorescent nanorods are outstanding candidates for fluorescent inks, due to their relatively low particle-particle interactions and self-absorption, the robust synthesis of mono-dispersed nanocrystals, their high quantum yields and their intrinsic emission polarization properties. We report here on the development of new ink formulations containing seeded semiconductor nanorods, which have unique and improved properties compared to the quantum dots. The inks demonstrate highly efficient method for maintaining the optical stability of fluorescent NPs in printing, by replacing the commonly used quantum dots. The advantages of seeded nanorods over quantum dots in inks were examined by comparing the optical properties of both solutions and patterns prepared with the two structures by ink-jet printing and low reabsorption and low interactions were demonstrated by negligible emission shifts upon printing, and maintaining the high fluorescence quantum yield, unlike quantum dots which display quenching effects.

 

 

 

 

[77] EXPERIMENTAL SYSTEM OF THE FULL SCATTERING PROFILE OF CIRCULAR PHANTOMS

 

Idit Feder¹, Hamootal  Duadi², Dror Fixler²

 

	1 Bar-Ilan University; Institute of Nanotechnology and Advanced Materials
	2 Bar Ilan University; Institute of Nanotechnology and Advanced Materials

 

 

Experimental system of the full scattering profile of circular phantoms

 

Idit Feder, Hamootal Duadi, Rinat Ankri and Dror Fixler

Faculty of Engineering and the Institute of Nanotechnology and Advanced Materials, Bar Ilan University, Israel

 

Abstract

Human tissue is one of the most complex optical media since it is turbid and nonhomogeneous. We suggest a new optical method for sensing physiological tissue state, based on the collection of the ejected light at all exit angles, to receive the full scattering profile. We simulate the light propagation in homogenous and heterogeneous cylindrical tissues and obtain the full scattering profile. In addition we built a unique set-up for noninvasive encircled measurement. We use a laser, a photodetector and tissues-like phantoms presenting different diameters and different reduced scattering coefficients. Our method reveals an isobaric point, which is independent of the optical properties and linearly depends on the exact tissue geometry. Furthermore, while adding nanoparticles to the tissue our new method can detect it due to the change they cause in the reduced scattering coefficient. In our previous work, nanoparticles have been defined as contrast agents for diagnostics and treatment of different physiological conditions, such as cancer and atherosclerosis. In addition, the blood vessels in human tissues are the main cause of light absorbing and also scattering. Therefore, the effect of blood vessels on light-tissue interactions is essential for biomedical applications based on optically sensing, such as oxygen saturation, blood perfusion and blood pressure. We show the vessel diameter influence on the full scattering profile, and found higher reflection intensity for larger vessel diameters accordance to the shielding effect. These findings can be useful for biomedical applications such as non-invasive and simple diagnostic of the fingertip joint, ear lobe and pinched tissues.

 

 

 

[91] MATERIAL DETECTION IN PHYSIOLOGICAL SUBSTANCES BY A NOVEL NONINVASIVE OPTICAL TECHNIQUE

 

Inbar Yariv¹, Hamootal  Duadi¹, Anat Lipovsky¹, Dror Fixler¹, Rachel Lubart²

 

	1 Bar Ilan University; Institute of Nanotechnology and Advanced Materials
	2 Bar Ilan University; Bar Ilan University

 

 

Physiological substances pose a challenge for researchers since their optical properties change constantly according to their physiological state. Examination of those substances noninvasively can be achieved by different optical methods with high sensitivity.

Our research suggests a novel noninvasive optical technique for the detection of materials in physiological substances. The optical technique is based on extracting the optical properties of substances, and especially the reduced scattering coefficient (µ_s‘). By examining the changes of the substance optical properties, detection of materials within it can be possible. The suggested optical technique, which examines the light reflection from and transmission through substances as shown in Figure 1, is based on iterative Gerchberg-Saxton (G-S) algorithm. It uses the multiple G-S algorithm for reconstructing the light phase created by the substance.  Changing the substance composition affects its optical properties which results with changes in the light phase that can be measured by the light phase standard deviation (STD).

The technique is implemented in two applications: the detection and depth determination of nanoparticles (NPs) in tissues and as an en route to the design of a novel milk-content-monitoring tool.

A simulation that calculates the light phase STD for different substances thickness and µ_s‘ was developed using reflection and transmission measurements. The results of the simulation indicate a linear ratio between the STD and the scattering components.
Applying the technique on detection of NPs within tissues, a linear ratio was also observed in the experiments of tissue-like phantoms and chicken skin with and without different types of NPs. The NPs presence within the tissue was observed by the change in STD which was up to 40% when the NPs were added.  
Appling the technique to design a monitoring tool for milk content, the effect of different milk components (Lactose and milk proteins) was examined. Our results show that we are able to detect the possibility of lactose and milk proteins’ quantitative signature.

 

Figure 1. The experimental setup.

 

 

 

[102] THREE-DIMENSIONAL METALLIC NETWORKS: AN INNOVATIVE SYNTHETIC STRATEGY AND OPTICAL PROPERTIES

 

Racheli Ron¹, Adi Salomon¹

 

1 Bar Ilan; Bar Ilan

 

 

Three-Dimensional Metallic Networks: An innovative synthetic strategy and optical properties

Racheli Ron, Adi Salomon

Department of chemistry, institution of nanotechnology, Bar-Ilan University.

Granting a large-scale piece of metal with a nanoscale architecture of a three-dimensional (3D) continues network provides a new material with novel optical properties. The network is made of interconnected metallic nano-sized ligaments of about 50 nm and connective percolating (open-cell) nano-pores. Such 3D metallic networks are colored similar to solution dispersed metallic silver and gold nanoparticles. Moreover, they exhibit high optical transparency and electrical conductivity. In regards with gold, silver and aluminum, these three-dimensional networks were found to support localized surface plasmon resonance (LSPR) and surface plasmon polaritons (SPP). Therefore, allow very high electromagnetic field enhancement in both large-scale and in three-dimensional manners. We characterize the unique opto-electronic properties of such metallic nano-architecture networks. Metal having this form can find potential applications in a great number of fields, such that functioning in photo-electric devices or as IR detectors since such gold networks possess very high transparencies at the near IR range.

 

 

 

[107] “POLARIMETRIC COLOR SORTER AT THE SUB-MICRON SCALE”

 

Elad Segal¹, Adam Weissman¹, David Gachet², Adi Salomon³

 

	1 Bar-Ilan University; Bar-Ilan University
	2 Attolight; Attolight
	3 Bar Ilan; Bar Ilan

 

 

“POLARIMETRIC COLOR SORTER AT THE SUB-MICRON SCALE”

Elad Segal ^a, Adam weissman ^a, David gachet ^b, and Adi Salomon ^a*

^a Department of Chemistry, Institute of Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat-Gan 52900, Israel.

^b Physics/Applications, Attolight AG, Lausanne, Switzerland.

 

Abstract: 

In this work we present an active plasmonic sub-micron device (fig. 1), which consists of a pentameric structure. The pentameric components are five identical triangular nano-cavities that are milled in a 200 nm silver opaque film. We use the hybridization between these metallic nano cavities to form new modes of plasmonic coupling, which is induced by a combination of localized and propagating surface plasmons (LSP and SPP). By tuning the polarization or the distance between these triangles, we are able to achieve suppression or enhancement of the field at specific frequencies. Herein, by minimizing the lateral device size to 200 nm (the triangular side-arm length), and less than 2 microns in length, we push the possible resolution to further increase. In addition, besides of transmission collection, we have closely inspected the fundamental behavior of the coupled entities by cathodo-luminescence (CL) measurements combined of spectra extraction and regional mapping.

 

 

 

 

 

 

 

Figure 1. “Rainbow of plasmonics”, the image depicts the simplicity of possible modes which can be obtained by easily changing either the polarization, or the distance between the coupled nano-triangular cavities (transmission image).

 

 

 

[113] DESIGNING PLASMON-MOLECULE INTERACTIONS

 

Lihi Efremushkin¹, Adi Salomon²

 

	1 Institute of Nanotechnology, Bar-Ilan University; Institute of Nanotechnology, Bar-Ilan University
	2 Bar Ilan; Bar Ilan

 

 

Designing Plasmon-Molecule Interactions

Lihi Efremushkin and Dr. Adi Salomon

Department of Chemistry, Institute of Nanotechnology, Bar-Ilan University, Ramat-Gan, Israel

 

In this work we show theoretically and experimentally that a molecular system at very low concentration can be strongly coupled to plasmonic modes. Upon coupling new hybrid states are formed, lower and higher polaritons. These modes have the characteristics of both molecular and plasmonic states and also new characteristic different from those of the molecular and plasmonic states. As the coupling strength grows increasing of molecular concentration asymmetric splitting is observed giving rise to enhanced transmission through metallic hole arrays. Moreover, we have also succeeded in reaching a linear dependency of the Rabi splitting value on the square root of the absorbance which is another proof for strong coupling.

We also show that by tuning the plasmonic modes we are able to be on/off resonance with respect to the molecular system and therefore generate new photonic-exciton hybrid states at different energies and as a consequence with unique properties. Moreover, we show that by changing the distance between the plasmons and the molecules we can design the strong interactions between the two systems.

 

 

 

[124] DESIGN OF A 1X2 SILICON-GALLIUM NITRIDE WAVELENGTH DEMULTIPLEXER BASED ON MULTIMODE INTERFERENCE IN SLOT WAVEGUIDE STRUCTURES

 

Dror Malka¹

 

1 Bar Ilan University; Bar Ilan University

 

 

Design of a 1×2 Silicon-Gallium Nitride Wavelength Demultiplexer based on Multimode Interference in Slot Waveguide Structures

Dror Malka^* and Zeev Zalevsky

 

Faculty of Engineering Bar-Ilan University, Ramat-Gan 52900, Israel

^*Corresponding author: dror.malka@biu.ac.il

Abstract

In this paper we present 1×2 wavelength demultiplexer operating at 1.3µm and 1.55µm wavelengths, based on multimode interference (MMI) coupler in slot waveguide structure. Gallium nitride was used as the slot material. The design is based on 1×2 MMI coupler demultiplexers.

Since the slot waveguide encompasses true guided modes, confined by total internal reflections, there are no noticeable confinement losses. Full vectorial-beam propagation method (FV-BPM) and BPM simulations were used for optimizing the device parameters and assessing its performance. To the best of our knowledge it is the first time that a 1×2 demultiplexer is being implemented by a slot waveguide based MMI.  In slot waveguide there is a strong electric field confinement in the low-index material (slot area) which leads to high power level in that region. This cannot be achieved in conventional waveguides, therefore there is a benefit using a slot-waveguide for realizing a 1×2 wavelength demultiplexer for optics communication.

Through simulation results, it has been shown that two wavelengths 1.3/1.55µm can be separated after propagation length of 150µm (Figs. 1(a)-(b)). The insertion losses of the proposed device are below 0.14dB for all two wavelengths and the cross talk is below -15dB. These low loss values indicate that such device can be used in wavelength division multiplexing (WDM) systems.

         (a)                                        (b)

Fig. 1. Intensity profile of the 1×4 MMI wavelength demultiplexer: (a). λ₁=1.55µm. (b). λ₂=1.3µm.

 

 

 

[130] ELECTRICAL EXCITATION AND IMAGING OF OPTICAL NANOPLASMONS

 

Moshik Cohen¹

 

1 Bar Ilan Universiry; Bar-Ilan Institute of Nanotechnology and Advanced Materials

 

 

Electrical Excitation and Imaging of Optical Nanoplasmons

Moshik Cohen* ^1,2, Yossi Abulafia² and Zeev Zalevsky^1,2

¹Faculty of Engineering, Bar-Ilan University, Ramat-Gan 52900, Israel

²Bar-Ilan Institute for Nanotechnology & Advanced Materials, Ramat-Gan 52900, Israel

 

When light interact with metals it may excite collective electronic excitations known as surface plasmon polaritons (SPPs). These electromagnetic waves are of high intensities and nanoscale dimensions, properties that enable horizons for new fundamental research directions alongside exciting applications ranging from energy harvesting to biomedical nano – imaging^1,2. It was experimentally observed that SPPs could also be excited using high-energy electron irradiation of nanometallic structures. However, direct imaging and nanomeasurements of SPPs using scanning electron beam is yet to be introduced. Here we experimentally demonstrate simultaneous direct excitation and rapid nano – imaging of optical plasmons, entirely based on scanning electron microscopy (SEM). We tested plasmonic slot waveguides coupled with dipole nanoantennas and quantitatively characterize both SPs and SPPs. Our results are supported by 3D numerical calculation and by an analytical model.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 1 | Plasmonic excitation and nanoimaging with Secondary Electrons. a, SEM topography mapping of the analyzed device obtained with low beam energy (5KeV) and current (25pA).b, SEM (SEE) response of the device under excitation via high energy, focused electron beam (50KeV, 2nm). c, 3D numerical simulation showing the electric field magnitude |E| of the device, when excited by a 50KeV, 2nm electron beam.  Scale bar: 100nm.      

 

To our knowledge, this is the first demonstration of all electrical excitation and imaging of optical plasmons, which rapidly generates high-resolution images and enables quantitative analysis. Our findings open new pathways for electrical investigation of optical nanoplasmonic devices; expanding the route towards merging electrons photons and plasmons on a single integrated platform.

 

1.Cohen, M., Zalevsky, Z. & Shavit, R. Towards integrated nanoplasmonic logic circuitry. Nanoscale 5, 5442–5449 (2013).

2.Cohen, M., Shavit, R. & Zalevsky, Z. Observing Optical Plasmons on a Single Nanometer Scale. Sci. Rep. 4, (2014).

 

 

 

 

 

[134] A SIMPLIFIED METHOD FOR GENERATING PERIODIC NANOSTRUCTURES BY INTERFERENCE LITHOGRAPHY WITHOUT THE USE OF AN ANTI-REFLECTION COATING

 

omree kapon¹

 

1 Bar-Ilan University; Bar-Ilan University

 

 

 

Abstract

 

Interference lithography has proven to be a useful technique for generating periodic sub-diffraction limited nanostructures. Interference lithography can be implemented by exposing a photoresist polymer to laser light using a two-beam arrangement or more simply a one beam configuration based on a Lloyd’s Mirror Interferometer. For typical photoresist layers, an anti-reflection coating must be deposited on the substrate to prevent adverse reflections from cancelling the holographic pattern of the interfering beams. For silicon substrates, such coatings are typically multilayered and complex in composition. By thinning the photoresist layer to a thickness well below the quarter wavelength of the exposing beam, we demonstrate that interference gratings can be generated without an anti-reflection coating on the substrate. We used ammonium dichromate doped polyvinyl alcohol as the positive photoresist because it provides excellent pinhole free layers down to thicknesses of 40 nm, and can be cross-linked by a low-cost single mode 457 nm laser, and can be etched in water.  Gratings with a period of 320 nm and depth of 4 nm were realized, as well as a variety of morphologies depending on the photoresist thickness. This simplified interference lithography technique promises to be useful for generating periodic nanostructures with high fidelity and minimal substrate treatments.

 

 

 

[140] TAILORING NANO-STRUCTURES TO ENHANCE THE RAMAN SCATTERING FROM FULLERENE C60

 

Miri Sinwani¹, Yaakov Tischler¹

 

1 Bar-Ilan Institute of Nanotechnology and Advanced Materials; Bar-Ilan University

 

 

Tailoring nano-structures to enhance the Raman scattering from fullerene C₆₀

Understanding the mechanism of surface enhanced Raman scattering (SERS) phenomena is essential for advancing SERS devices for developing the next generation of Raman sensors. Conventional studies investigate the excitation wavelength dependence for certain nanostructure morphologies. However, more comprehension of SERS mechanism can be gained when combining the excitation wavelength dependence with the metal morphology dependence. Here, we report a SERS study of Fullerene C₆₀ thermally evaporated on Au thin film (40 nm) with dense nano-island morphology, and on Au ultra-thin film (2 nm) with nanoparticle morphology. Each sample was measured with two excitation wavelengths: 532 nm and 784 nm. Excitation wavelength of 532 nm generated similar SERS spectra from both Au surfaces. In addition, these SERS spectra fully correlated with regular Raman spectra, strongly indicating a resonance Raman mechanism. In contrast, excitation wavelength of 784 nm caused different SERS spectra in which the SERS intensity, measured from the Au ultra-thin film surface, was 10 times higher than the SERS signal from the Au thin film. The spectral diversity implies an electromagnetic mechanism controlled by near field interactions of local surface plasmon resonances (LSPR).  To strengthen our conclusions, we measured the emission spectrum of each Au surface with both 532 nm and 784 nm excitation wavelengths. While the emission spectra with 784 nm excitation revealed LSPR that correlated with the SERS spectra, the emission spectra of 532 nm excitation did not correspond with the obtained SERS spectra. This connection between emission spectra and SERS spectra of the C₆₀ molecule is attributed to the LSPR overlapping with the energy level manifold of the C₆₀.    

 

 

 

[141] MINIMAL INVASIVE MICRO-ENDOSCOPE IMAGING IN SCATTERING MEDIA ENVIRONMENT

 

omer wagner¹, Aditya Pandya², Irina Schelkanova², Asaf  Shahmoon¹, Alexandre  Douplik², Zeev Zalevsky³

 

	1 Bar Ilan Uni.; Bar Ilan Uni.
	2 Ryerson University; Ryerson University
	3 Bar Ilan University; Bar Ilan University

 

 

 

Minimal invasive micro-endoscope imaging in scattering media environment

 

Omer Wagner^1,*, Aditya Pandya², Irina Schelkanova², Asaf Shahmoon¹, Alexandre Douplik², and Zeev Zalevsky¹

 

¹Faculty of Engineering, Bar-Ilan University, Ramat-Gan 52900, Israel

²Physics Department, Ryerson University, Toronto, Canada

 

Abstract –

Imaging through scattering media is a very applicative field, especially for minimal invasive imaging in biomedical research, medicine etc where imaging through tissues pose a big challenge. Common micro endoscope configurations use gradient refractive index (GRIN) microlenses, which allow wide imaging range. However, the GRIN lens is limited by the mechanical rigidity, length and endoscopes diameter, which may prevent it to reach deep internal organs without damaging their functionality. A different micro endoscope configuration is based on multi core fiber. In this case, the imaging device consists of a few thousand and up to a few tens of thousands of step-index single mode cores which are incorporate together to perform the required imaging operation. The fiber is hard contacted to the sample.         
In this work we use a specially fabricated micro endoscope multi core fiber having cores of 0.5 micron in size with 2 micrometer pitch between cores, to image samples that are located inside an environmental scattering media. We have succeeded to image 30 µm in tissue channels (e.g. blood vessels) through a scattering media of up to 360 µm thick with scattering coefficient of μ_s’=0.993mm^-1.

 

 

 

 

[149] SECOND HARMONIC GENERATION FOR ELECTRODE SURFACE IMAGING

 

hannah aharon¹, Adi Salomon²

 

	1 Bar Ilan University ; Max and Anna Webb
	2 Bar Ilan; Bar Ilan

 

 

Second Harmonic Generation for Electrode Surface Imaging

Hannah Aharon and Adi Salomon

Understanding the chemistry on the surface of electrochemical electrodes is a major obstacle in the development and understanding of rechargeable batteries and fuel cells. With our lab built Second Harmonic Generation (SHG) setup, we look into these interactions by means of nonlinear optics. SHG generation is blind to any bulk centrosymmetric material and can therefore be focused on the electrode surface without interference from the bulk electrode or the electrolyte. Following the changes the electrode undergoes due to voltage, electrochemical charging and discharging etc. are made feasible due to our custom made battery cell. These measurements are performed in- and ex-  situ. We show that even the slightest bias applied to an electrode effects the SHG signal. This is due to the unique sensitivity of SHG electrostatic properties and polarization of surfaces.

 

 

 

[170] TWEEZERS CONTROLLED RESONATORS

 

Samuel Kaminski¹

 

1 Technion; 32000

 

 

Tweezers Controlled resonators

 

We experimentally demonstrate trapping a  micro-droplet with an optical tweezers and then functionalize it as a micro-resonator by bringing it close to a tapered fiber coupler.  Our tweezers facilitated tuning of the coupling from the under-coupled to the critical coupling regime with an optical Q of 12 million and micro-resonator size at the 85 um scale. We prove the concept of using an optical trap for activating oil droplets as fiber-coupled micro-resonators. We believe that our technique will extend to several resonators and then to an optical circuit where the shape and position of many optical devices will be controlled.

 Our long-term vision includes optical circuits where a multi-minima optical trap shapes and positions multiple resonators. Being practical, we start here with modestly proving this concept by activating one µdrop as a resonator, and using an optical trap to hold and position it next to a tapered-fiber coupler.

 

 

 

[176] REINTERPRETING THE MAGNETOELECTRIC COUPLING OF INFINITECYLINDERS USING SYMMETRY: A SIMPLE TM/TE VIEW

 

Parry Chen¹, Jacob Ben-Yakar¹, Yonatan  Sivan²

 

	1 School of Physics and Astronomy, Raymond and Beverly Sackler Faculty of Exact Sciences; Tel Aviv University
	2 Unit of Electro-Optical Engineering; Ben Gurion University

 

 

Periodic arrays of long circular cylinders, whether metallic or dielectric, are key components of many metamaterial designs. These include all-dielectric optical metamaterials, hyperbolic media, super-resolution endoscopes, drawn metamaterial fibers, and single-molecule bio-sensors. Characterizing the response of individual cylinders is a fundamental step towards the effective electromagnetic response. For optically thin cylinders, scattering is adequately described by dipoles, considerably simplifying subsequent treatment by effective medium theories, ultimately yielding ε and μ.

This proceeds by analogy to the polarizability tensor α of a molecule. When α is diagonal, only electric fields can induce electric dipoles. A general metamaterial element may also have non-zero off-diagonal blocks, representing magnetoelectric coupling whereby magnetic fields induce electric dipole moments. Despite its fundamental importance, the literature retrieving the full polarizability tensor of cylinders is sparse, considered by only one publication to our knowledge. Surprisingly, a magnetoelectric coupling was reported [1], which only arises in non-centrosymmetric scatterers such as split ring resonators.

We delve into the physical origins of this coupling, establishing insight which is critical to the design of metamaterials exhibiting artificial magnetism. We show that a simple decomposition of α into its TM/TE components restores the expected diagonal response through a transformation we derive, supplying an analytically simpler formulation. Our key insight is that off-diagonal magnetoelectric coupling terms account for the difference between TM/TE responses, allowing two dissimilar diagonal responses to be combined onto a single tensor.

This provides ready explanations for the unusual magnetoelectric coupling of infinite cylinders, which for example changes sign when angles of incidence are inverted, and disappears when counterpropagating waves are impinging. Our analysis explains why magnetoelectric coupling exhibits weak k⁴ scaling for dielectric cylinders at long wavelengths, k² scaling for perfect electric conductors, but becomes prominent at Mie resonances. Unlike structures without inversion symmetry though, the strengths of magnetoelectric resonances cannot differ from both its corresponding electric and magnetic resonances.

[1] D. Strickland et al., PRB 91 (8), 085104 (2015)

 

 

 

[210] NOVELL XUV SPECTROMETER FOR NANOMATERIAL ANALYSIS IN SCANNING ELECTRON MICROSCOPE

 

Alexei Erko¹, Aljosa Hafner¹, Alexander Firsov¹

 

1 Institute for Nanometer Optics and Technology; Helmholtz Zentrum Berlin

 

 

Nano- structuring technology: e-beam lithography and reactive ion etching, were used for fabrication of spectrometric X-ray optical elements with minimal structure period down to 80 nm. Here we are reporting on a 17-element, 14-element (both discrete energy) and a 200-element (quasi-continuous) reflection zone plate (RZP) spectrometer, newly designed for XUV fluorescence emission spectra analysis of nanomaterials with scanning electron microscopes. The 14-channel optical element is designed specifically for X-ray emission spectra of ultralight elements such as Mg and Li compounds, Al L- and Si L-lines in the energy range of 45 eV – 100 eV. The 17-channel optical element covers an energy range from 54 eV to 1120 eV. The energy resolution, measured on the Al L-peak to be 0.5 eV eV and the overall resolving power is on the order of E/ΔE ~ 80-160.

 

1. Hafner et al., Optics Express, 23, (23), (2015), 29476
2. A Erko et al., Optics Express 22 (14), (2014), 16897-16902

 

 

 

[216] NANO-ANTENNAS FOR SPATIAL ADDRESSING OF SPIN STATES IN DIAMONDS

 

Tzach Jaffe¹

 

1 Technion; Israel Institute of Technology

 

 

 

Nano-antennas for Spatial Addressing of Spin States in Diamonds

Tzach Jaffe, Ofir Sorias and  Meir Orenstein.

 Department of Electrical Engineering, Technion – Israel Institute of Technology, 32000 Haifa, Israel.

tzahifa@tx.technion.ac.il

Abstract: The negatively charged Nitrogen-Vacancy (NV) color center in diamond is an important physical system for emergent quantum technologies and sensing at room temperature. We propose and experimentally demonstrate a selective and spatially localized way to address the spin states of the NV center, by a plasmonic antenna tuned to modify the NV’s emission and absorption spectra.

The NV center is a multi-electron system which allows us to address its spin state with optical light. Different methods for addressing and controlling the spin states of NV centers have been thoroughly investigated in recent years, but currently there is no efficient way to selectively address NV center in regular bulk diamond. In order to achieve that, we have to overcome the inherent mismatch between the wavelength of excitation and the size of the NV center, and at the same time to modify its emission and absorption spectra. For that reason we chose to combine the NV’s properties with localized plasmonics.

We investigated theoretically and experimentally a specific plasmonic antenna, denoted here as the “Templar Cross (TC) Antenna”, in order to enhance the excitation power and to increase the photonic density of states for enhanced emission, in its vicinity. We experimentally demonstrate performance enhancement which highlights its potential for spatial control over initialization and readout of the system’s spin state, with a polarization dependency (Figure 1).

Figure 1 – (a) SEM image of a TC antennas array; (b) Reflection measurement from the array for two polarizations – X and Y; (c,d) NSOM measurement and near field simulation results of the intensity enhancement (up to 3 orders of magnitude) due to two types of resonances in the structure (Logarithmic scale colorbar); (e,f) Measurements of the NV’s NIR and visible emission spectra respectively.

 

 

 

[244] DIRECT 3D NANOPRINTING ON FIBER TIP OF COLLIMATING LENS AND OAM MODE CONVERTER IN ONE COMPOUND ELEMENT

 

Israel Weiss¹, Dan Marom¹

 

1 Hebrew University of Jerusalem; Applied Physics Department

 

 

Optical fibers are widely used as an efficient and flexible light transmission medium that is well protected from the environment. The fiber facet is an opportune location for placement of structures and devices for interaction with light.

Here we present 3D nano printing process directly on optical fiber tip using a commercial 3D laser lithography system of “Nanoscribe GmbH” employing immersion technology. We optimized the fabrication process in terms of surface smoothness, volume homogeneity and writing speed in order to reach high optical quality of the fabricated elements. This ability gives us wide leeway for realizing sophisticated optical elements in the nano-scale in order to control the light efficiently and accurately at the fiber tip. In that project we demonstrate the direct nanoprinting of a 3D collimating lens suspended above the fiber with an azimuthal phase for creating an OAM beam.

As a preliminary step, we printed the device on a flat glass substrate. By projecting light on the device through a cleaved fiber, we were able to observe the OAM ring intensity profile (Figure 1 a) as well as the interference pattern with the Gaussian mode (Figure 1 b,c), by adjusting the distance between the fiber and the device.

Next, we designed and fabricated a spherical lens with azimuthal spiral phase plate on top of it. The lens was designed with radius of curvature of 25um, meaning focus length of about 50um (Figure 2, Designed sketch (a) and SEM images (b-d) of the device). The spiral phase plate is encoded on top of the spherical lens with the same radius of curvature, and with a phase step of 2pi along a radius section of the device. The whole structure is printed on top of supporters with height of 50um, designed so that the light will be collimated at the exit of the device.

 

 

 

[331] ULTRAFAST PULSE GENERATION USING TRANSIENT BRAGG GRATINGS IN OPTICAL FIBERS & WAVEGUIDES

 

Aviran Halstuch¹

 

1 Hagefen 56; Hagefen 56

 

 

Ultrafast pulse generation using transient Bragg gratings in optical fibers & waveguides

Aviran Halstuch, Shai Rozenberg, Amiel A. Ishaaya, Yonatan Sivan
Faculty of Engineering Sciences, Ben-Gurion University of the Negev, Israel

Commercial fiber lasers are currently operational only at a limited set of wavelengths (e.g 1µm, 1.5µm, 2µm) or other few operational wavelengths generated by nonlinear conversion based on chi-2 materials or Raman amplification. It is also known that such lasers with pulse durations between several picoseconds to 1 nanosecond are indeed scarce, since this regime is between Q-switching and mode-locking.

In this work we introduce and demonstrate theoretically a flexible yet simple scheme to generate ultrashort pulses at arbitrary wavelength and duration via spectral inheritance, whereby a spectrally-narrow pulse “inherits” the wide spectrum of a pump pulse centered at a different wavelength. Moreover, our scheme provides a new route for spatio-temporal pulse shaping and further practical advantages such as pulse-to-pulse control.

The suggested scheme enables such spectral “inheritance” by introducing a transient Bragg grating (TBG) in an optical waveguide/fiber. The TBG can be induced via Cross-phase modulation in Kerr media, or more efficiently using free-carrier or even thermal nonlinearities. Various parameters such as: spatial profile, temporal profile, intensity and wavelength, of the induced TBG affect the duration and intensity of the reflected pulse generated.

The concept was demonstrated via exact numerical solution of the Maxwell equations by using FDTD methods. A simplified model was derived based on an extension of standard coupled mode theory equations. We show excellent agreement between these various approaches.

Specifically, we demonstrate backward pulse durations of ~150-200ps in silica fibers. Shorter pulses down to ~ 1ps can be generated at lower efficiencies. However, improved efficiency level up to ~50% can be achieved for such short pulses by using a stronger, slower nonlinear process, e.g., free carrier nonlinearity in silicon.

Finally, we review the experimental demonstration of spectral inheritance in both silica fibers and silicon waveguides.

 

 

 

 

 

 

[346] LASER AND PLASMONIC COUPLED MODES

 

shir shahal¹, Hamootal  Duadi², moti Fridman¹

 

	1 Bar Ilan University; Institute for Nanotechnology and Advanced Materials
	2 Bar Ilan University; Institute of Nanotechnology and Advanced Materials

 

 

Laser and plasmonic coupled modes

Shir Shahal, Hamootal Duadi and Moti Fridman 

Faculty of Engineering and the Institute of Nanotechnology and Advanced Materials, Bar Ilan University, Ramat Gan, 52900, Israel

Excitation of free electrons which oscillate in resonance along a metal surface, are called Surface Plasmon Polaritons (SPPs). SPPs have been the subject of intensive research for the past few decades, and play a role in manipulating electromagnetic fields from the visible to the infrared spectra, both in linear and non-linear optics. Periodic hole arrays in a metal film are convenient structures to achieve the coupling of light to SPPs, since their spectral properties can be tuned and scaled by adjusting the size and geometry of the holes. When a light beam is in resonance with the periodic hole array the transmission of light is increased. This effect is called enhanced transparency.

Until now there was a little research about the spatial plasmonic modes in enhanced transparency. We investigate the spatial modes of enhanced transparency in gold and tungsten films, which have a periodic sub-wavelength hole array, by imposing interaction between the SPPs modes and the spatial modes of a laser diode.

Our experiment is based on placing a sub-wavelength hole array written on a metal plate at the focal plane of a degenerate cavity laser and measuring the transmission modes. As a first step we placed a single, variable size slit at the focal plane, and measured the transmission modes through the plate.

We will present our current results, along with our experimental set up and methods.   

 

 

 

[350] NONLINEAR WAVE MIXING IN PLASMONIC STRUCTURES : A TRANSFORMATION OPTICS

 

Nireekshan Reddy Kothakapu¹, Antonio Fernandez-Dominguez², Yonatan  Sivan³

 

	1 Ben-Gurion University; Ben-Gurion University
	2 Universidad Autonoma de Madrid; Universidad Autonoma de Madrid
	3 Unit of Electro-Optical Engineering; Ben Gurion University

 

 

Nonlinear Wave Mixing in Plasmonic Structures : A Transformation Optics

1. Nireekshan Reddy¹, Antonio I. Fernandez-Dominguez² and Yonatan Sivan¹

1) Unit of Electro-Optic Engineering, Ben-Gurion University, Beer-Sheva 8410501,Israel

2) Departamento de Fisica Teorica de la Materia Condensada, Universidad Autonoma de

Madrid, E-28049 Madrid, Spain.

Keywords:  Nano-Optics, Second-Harmonic Generation

 

Singular structures in plasmonics, for example, touching wires, crescent cylinders, etc., are well known for enhancing the field in small volumes by several orders of magnitude. Recent studies revealed that transformation optics can provide a very powerful analytical tool to solve these class of problems. It was also pointed out that these class of structures can also be suitable candidates for energy harvesting and field enhancements were calculated to be as high as 10⁴ close to singular points. We review some of the theoretical and the experimental results of the linear properties of these structures.

Such high field enhancement would definitely invoke the nonlinear phenomenon. Our present study analytically incorporates such nonlinear phenomenon from χ⁽²⁾ materials initially focusing on second-harmonic generation. We follow the route of conformal transformation optics but now extending it to nonlinear materials. To the best of our knowledge there have been no reports on such analytical techniques describing nonlinear optics at nanoscale. We identify the relations for phase and amplitude matching for the second-harmonic fields. Our approach also connects with the standard coupled-mode theory used in “macro-optics” structures such as waveguide to the Green’s function approach which is extensively used in nano-optics. We identify the optimal conditions for second-harmonic generation efficiency. This approach is the starting point to understand various other nonlinear interactions such as three and four-wave mixing in singular structures.

References:

 [1] J. B. Pendry, A. Aubry, D. R. Smith, S. A. Maier,Transformation Optics and Subwavelength Control of Light,” Science 337, 549 (2012)

 

 

 

[382] EXCITATION OF LP MODES THROUGH LPFG

 

Gilad Masri¹, Mordechai Fridman¹, Shir Shahal¹, Hamootal  Duadi²

 

	1 Bar-Ilan University; Institute of Nano Technology
	2 Bar Ilan University; Institute of Nanotechnology and Advanced Materials

 

 

15.11.2015

Bar-Ilan University

Faculty of Engineering

Excitation of LP modes through LPFG

Gilad Masri, Shir Shahal, Hamutal Duadi, Moti Fridman

Faculty of Engineering and the BINA center for nanotechnology, Bar Ilan University

            We present a method for exciting linearly polarized (LP) Electromagnetic Field modes with a Long-Period Fiber Grating (LPFG). We wrote the LPFG by tailoring the mechanical oscillations of a fiber while tapering it. We investigated the output mode as a function of the input wavelength, and found that the LPFG causes energy transfer from the LP₀₁ Gaussian-profile mode to higher LP_lm modes for specific input wavelengths. The results are compared to a calculated model. In this model we relate the modal dynamic of the light to variations in the spatial direction of the light’s photon momentum imposed by the LPFG. This research can lead to a new method of real-time spectral detection of light sources and the ability to decompose the EM Field into several LP_lm modes. Potential applications are wavelength-sensitive sensors for temperature, chemical and mechanical stress analysis. The experimental scheme and results together with the calculated results will be presented.

 

 

 

[402] “NOVEL SILICON NANOWIRES COLOR DETECTORS FOR THE USE IN OPTOELECTRIC APPLICATIONS”

 

Sharon Lefler¹

 

1 Group of Prof” Patolsky, School of Chemistry, Raymond and Beverly Sackler Faculty of Exact Sciences,; Center for Nanoscience and Nanotechnology

 

 

The absorbance spectrum of silicon lays under ~1,1000nm which enables silicon to detect visible light. However silicon-based photo detectors cannot distinguish between different wavelengths. Therefore, these detectors relay on color-specific pre-filters to achieve color separation. These color filters add complexity to color sensitive device fabrication and hinder the miniaturization of such devices. Only recently, the first color-specific non-silicon based detectors were reported, utilizing complex thick, and thin, film photodiodes based on perovskite crystals. Nevertheless, these perovskite-based photodetectors are at a millimeter-scale, and cannot be incorporated into present silicon-based integrated circuits. Here, we present the use of novel molecularly-embedded silicon nanowires (SiNWs) which can detect different and specific wavelengths, without the use of filters or waveguides. These Nano Color-Specific Field Effect Transistors (NCS-FETs) can detect at least 4 distinct colors, red- green-blue-UV (RGB+UV). Upon wavelength specific excitation, the NCS-FETs can retain significant part of their current for long periods of time, post excitation, serving as memory elements. We can also control the ‘on’-‘off’ state of the NCS-FETs all-optically, without the use of electric gate. These NCS-FETs devices operate well under ambient conditions, and were found to be stable for months from their fabrication date. All together, these NCS-FETs can be utilized in many experimental and commercial applications, ranging from small pixel-size photodetectors, nonvolatile optoelectric memory devices and bio-sensing related applications.

 

 

 

 

[406] TAILORING LIGHT BY 3D DIRECT LASER-WRITING FABRICATED MICROSTRUCTURES

 

shlomi lightman¹

 

1 Tel Aviv University; Tel Aviv University

 

 

Tailoring light by 3D direct laser-writing fabricated microstructures

Shlomi Lightman^1,3, Raz Gvishi¹, Ehud Galun², and Ady Arie³

¹Electro-optics Division, Soreq NRC, Yavne 81800, Israel

²DDR & D IMOD, Hakirya, Tel Aviv, Isarel

³Department of Physical Electronics, School of Electrical Engineering, Tel Aviv University, Tel Aviv 69978, Israel

 

The ability to manipulate light beams has become a key factor in many areas of science, as it is possible to generate beams of complex structures. Hence, an astonishingly wide range of prospective applications have emerged because of this capability: noncontact optical manipulation of matter (optical tweezers), subwavelength resolution microscopy, nanofabrication, laser cooling (atom trapping) and so on. Many of these methods exploit the distinctive properties of each generated beam, such as phase properties, spatial intensity distributions and (orbital\spin) angular momentum. These new light beams can be generated in several ways, as the key element is the change of phase or amplitude of the original beam. In principle, phase modulation is a better approach than amplitude modulation, mainly since the latter is lossy and splits the incoming beam into multiple diffraction orders. The conventional ways of generating phase modulation have several drawbacks, as custom-made optical devices are usually manufactured by a long, multiple-step, fabrication process; and electrically driven liquid-crystal mediums, i.e. spatial light modulators, are expensive, planar and cannot be integrated. Here we demonstrate phase modulation of light beams, by harnessing a 3D-Direct laser writing lithography process. With this fabrication capability, arbitrary micron-scale structures can be written directly onto optical elements (e.g. nonlinear crystals, lenses and various substrates), as they modify the phase of the incoming light, by corresponding to a desired phase modulation. This enables structuring complicated beams, acquire mode sorting capability of orbital angular momentum beams, and reduce lens aberrations by correcting elements, in a compact, stable and cost effective routine.

 

 

 

 

 

[416] EXPERIMENTAL SYSTEM OF THE FULL SCATTERING PROFILE OF CIRCULAR PHANTOMS

 

Idit Feder¹, Hamootal  Duadi², Dror Fixler²

 

	1 Bar-Ilan University; Institute of Nanotechnology and Advanced Materials
	2 Bar Ilan University; Institute of Nanotechnology and Advanced Materials

 

 

Experimental system of the full scattering profile of circular phantoms

Idit Feder, Hamootal Duadi, Rinat Ankri and Dror Fixler

Faculty of Engineering and the Institute of Nanotechnology and Advanced Materials, Bar-Ilan University, Israel

Human tissue is one of the most complex optical media since it is turbid and nonhomogeneous. We suggest a new optical method for sensing physiological tissue state, based on the collection of the ejected light at all exit angles, to receive the full scattering profile. We simulate the light propagation in homogenous and heterogeneous cylindrical tissues and obtain the full scattering profile. In addition we built a unique set-up for noninvasive encircled measurement. We use a laser, a photodetector and tissues-like phantoms presenting different diameters and different reduced scattering coefficients. Our method reveals an isobaric point, which is independent of the optical properties and linearly depends on the exact tissue geometry. Furthermore, while adding nanoparticles to the tissue our new method can detect it due to the change they cause in the reduced scattering coefficient. In our previous work, nanoparticles have been defined as contrast agents for diagnostics and treatment of different physiological conditions, such as cancer and atherosclerosis. In addition, the blood vessels in human tissues are the main cause of light absorbing and also scattering. Therefore, the effect of blood vessels on light-tissue interactions is essential for biomedical applications based on optically sensing, such as oxygen saturation, blood perfusion and blood pressure. We show the vessel diameter influence on the full scattering profile, and found higher reflection intensity for larger vessel diameters accordance to the shielding effect. These findings can be useful for biomedical applications such as non-invasive and simple diagnostic of the fingertip joint, ear lobe and pinched tissues.

 

 

 

[420] FEMTOSECOND-SCALE SWITCHING BASED ON EXCITED FREE-CARRIERS

 

marat spector¹, Yonatan  Sivan²

 

	1 Ben Gurion University of the Negev; Ben Gurion University of the Negev
	2 Unit of Electro-Optical Engineering; Ben Gurion University

 

 

Femtosecond-scale switching based on excited free-carriers

 

 

Ultrafast switching is one of the oldest and most important applications of nonlinear optics. Traditionally, it is based either on Kerr nonlinearity, which is instantaneous, but weak, or on free carrier nonlinearity, which could be much stronger, but comes at the cost of a substantially slower turn-off time.

 

Here, we demonstrate simple schemes that enable us to enjoy the best of the two worlds – to have an ultrafast and strong switching, based on free-carrier generation. Specifically, we describe novel switching schemes operating on femtosecond time scales, which are based on a periodic pattern of free-carriers (FCs) which serves as a transient Bragg grating. Such gratings can be generated by a resonant pumping of a semiconductor or metallic waveguide.

 

In the first realization, we rely on diffusion to erase the initial FC pattern, hence, to remove the reflectivity of the system. We show that the grating erasure time is quadratically proportional to the effective wavelength, so that the high refractive index of semiconductors or the effective index of plasmonic waveguides makes this time scale sub-picosecond under realistic conditions. In the second realization, we erase the FC pattern by launching a second, delayed pump pulse which is shifted by half a period compared with the first one.

 

We discuss the advantages and limitations of the proposed approach and demonstrate it for switching ultrashort pulses propagating in silicon waveguides and plasmonic waveguides. We show reflection efficiencies of up to 50% for 100fs pump pulses, which is an unusually high level of efficiency for such a short interaction time, a result of the use of the strong FC nonlinearity.

 

Due to limitations of saturation and pattern effects, the scheme can be employed for switching applications requiring femtosecond features but standard repetition rates. Such applications include switching and modulations of ultrashort pulses, femtosecond spectroscopy (gating) and time-reversal of short pulses for aberration compensation.

 

 

 

[441] BROADBAND NEAR-INFRARED TO VISIBLE UPCONVERSION IN QUANTUM DOT-QUANTUM WELL HETEROSTRUCTURES

 

Ayelet Teitelboim¹, Dan Oron²

 

	1 Dept. of Physics of Complex Systems, Weizmann Institute of Science, Rehovot, Israel; Weizmann Institute
	2 Department of Physics of Complex Systems; Weizmann Institute of Science

 

 

Broadband near-infrared to visible upconversion in quantum dot-quantum well heterostructures

 

Ayelet Teitelboim, Dan Oron.

1. Department of Physics of Complex Systems, Weizmann Institute of Science, Rehovot, Israel, 7610001

Abstract:

Upconversion is a nonlinear process in which two, or more, long wavelength photons are converted to a shorter wavelength photon. It holds great promise for bioimaging, enabling spatially resolved imaging in a scattering specimen and for photovoltaic devices as a mean to surpass the Shockley-Queisser efficiency limit. Here, we present dual near-infrared and visible emitting PbSe/CdSe/CdS nanocrystals able to upconvert a broad range of NIR wavelengths to visible emission at room temperature. The synthesis is a three-step process, which enables versatility and tunability of both the visible emission color and the NIR absorption edge. Using this method one can achieve a range of desired upconverted emission peak positions with a suitable NIR band gap.

 

 

 

[469] PHOTONIC AND PLASMONIC NANO-SCALE LIGHT VAPOR INTERACTIONS

 

Liron Stern¹, Boris Desiatov¹, Meir Grajower¹, Noa Mazurski¹, Uriel Levy¹

 

1 Hebrew University of Jerusalem; Department of Applied Physics, The Benin School of Engineering and Computer Science, The Center for Nanoscience and Nanotechnology

 

 

Photonic and Plasmonic Nano-Scale Light Vapor Interactions

Liron Stern, Boris Desiatov, Meir Grajower,  Noa Mazurski and Uriel Levy*

Department of Applied Physics, The Benin School of Engineering and Computer Science, The Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Jerusalem, 91904, Israel

 

Alkali vapors, such as rubidium, are being used extensively in several important fields of research such as slow and stored light non-linear optics quantum computation, atomic clocks and magentometers. Lately, there is a growing effort towards miniaturizing traditional centimeter-size vapor cells. Owing to the significant reduction in device dimensions, light matter interactions are greatly enhanced, enabling new functionalities due to the low power threshold needed for non-linear interactions. Here, we demonstrate the evanescent interaction of both photonic and plasmonic optical modes with Rubidium atoms. First, we demonstrate light-matter interactions in a new generation of atomic cladding wave guide, namely an atomic cladding serpentine waveguide, consisting of a 17mm long silicon nitride nano-waveguide core with a rubidium vapor cladding. We observe the efficient interaction of the electromagnetic guided mode with the rubidium cladding and demonstrate all optical control on a probe signal in the microwatt power regime. Next, we present a novel hybrid plasmonic-atomic system, consisting of a prism coated with a 40nm gold layer integrated with an atomic cell. Using this platform, we demonstrate  the resonance coupling of a surface Plasmon resonance and Rubidium atomic vapor. By introducing a magnetic field, we are able to control the Fano line shapes, and observe the unique selection rules subject to the existence of an evanescent longitudinal electric field component. Both the plasmonic and photonic integrated platforms, are expected to serve as an important building blocks in future applications such as magnetometry, chip scale frequency standards and pulse shaping.  

 

 

 

 

 

 

[472] SPECTROSCOPIC INSIGHT INTO THE INFLUENCE OF CATION EXCHANGE ON THE ANIONIC FRAMEWORK OF QUANTUM DOTS

 

Noga Meir¹, Beatriz Martin-Garcia², Iwan Moreels², Dan Oron¹

 

	1 Department of Physics of Complex Systems; Weizmann Institute of Science
	2 Department of Nanochemistry; Istituto Italiano DI Technologia

 

 

 

 

Spectroscopic Insight into the Influence of Cation Exchange on the Anionic Framework of Quantum Dots

Noga Meir, Beatriz Martin-Garcia, Iwan Moreels, Dan Oron

 

The process of cation exchange in semiconducting nanocrystals has been in use for many years as an important synthetic tool. However, not much attention was given to the possible effect such process can have on the anionic framework of the crystal.

In this study, we used CdSe quantum dots that are doped by only one or a few atoms of Te. These quantum dots exhibit large blue-shift of the biexciton energy due to the presence of the Te dopant. This energy shift is strongly dependent on the size of the CdSe host and the location of the Te dopant. By using simple spectroscopic methods we were able to measure the biexciton energy before and after a back-and-forth cation exchange process (from Cd²⁺ to Zn²⁺ and back to Cd²⁺), and use these measurements in order to assess the effect of the cation exchange process on the crystal structure of the dots.  

 

 

 

[477] SYNTHESIS AND OPTICAL PROPERTIES OF THIN FILMS COMPOSED FROM WS2 NANOTUBES DECORATED WITH GOLD NANOPARTICLES

 

Alexander Polyakov¹, Varvara Zubyuk², Tatiana Dolgova², Lena Yadgarov³, Bojana Visic⁴, Andrey Fedyanin², Reshef Tenne⁵, Eugene Goodilin¹

 

	1 Lomonosov Moscow State University; Faculty of Materials Science
	2 Lomonosov Moscow State University; Faculty of Physics
	3 Weizmann Institute of Science; Department of Materials and Interfaces
	4 Weizmann Institute of Science ; Department of Materials and Interfaces
	5 Department of Materials and Interfaces; Weizmann Institute of Science

 

 

Synthesis and Optical Properties of Thin Films Composed from WS2 Nanotubes Decorated with Gold Nanoparticles

Alexander Polyakov,¹ Varvara Zubyuk,² Tatiana Dolgova², Lena Yadgarov,³ Bojana Visic,³ Andrey Fedyanin,²  Reshef Tenne,³ Eugene Goodilin¹

¹ Lomonosov Moscow State University; Faculty of Materials Science, Moscow, Russian Federation

² Lomonosov Moscow State University; Faculty of Physics, Moscow, Russian Federation

³ Weizmann Institute of Science; Department of Materials and Interfaces, Rehovot, Israel

Thin films of WS₂ nanotubes (INT-WS₂) decorated with gold nanoparticles are prepared using nanocomposite assemblage on the water-heptane interface and film transition onto optically transparent or semiconducting surfaces. Almost all nanotubes were found to be aligned horizontally within the 1-2 layered films. The film morphology resembles a mosaic structure of 10-25 square micron areas with in-plane textured nanotubes. Within these areas, composite particles change the reflected light polarization identically, as visualized optical microscopy in a near-crossed analyzer configuration. Optical extinction spectra of the films demonstrate several features around 490, 545, and 675 nm similar to the ones in suspension spectra, but with altered intensity ratio, possibly due to high anisotropy of the nanotubes and their texturing peculiarities in the films. At the same time, decoration with gold nanoparticles did not result in appearance of any additional peaks in both suspension and film spectra of the nanocomposites relative to the ones of pristine nanotubes. The same was observed previously for Au-INT-WS₂ suspensions and described by low-barrier contact between gold nanoparticles and nanotubes. Reflectance spectra of the INT-WS₂ and Au-INT-WS₂ films measured using a p-polarized beam revealed an angular dependence of both films reflectance spectra, thus evidencing for the possibility of new optical applications of WS₂-based materials in the future.

AYP and EAG thank The Russian Scientific Foundation for financial support (grant 14-13-00871). AYP thanks the Personal Studentship of RF President for young scientists and Ph.D. students (agreement SP-4789.2015.1).

 

 

 

[485] DIRECT OBSERVATION OF ELECTROMAGNETIC NEAR FIELD IN SILICON NANOPHOTONICS DEVICES USING SCANNING THERMAL MICROSCOPY (STHM) TECHNIQUE

 

Meir Grajower¹, Liron Stern¹, Boris Desiatov¹

 

1 Hebrew University of Jerusalem; Department of Applied Physics, The Benin School of Engineering and Computer Science, The Center for Nanoscience and Nanotechnology

 

 

Direct observation of electromagnetic near field in nanophotonics devices using Scanning Thermal Microscopy (SThM) technique

 

Meir Grajower, Liron Stern, Boris Desiatov, Ilya Goykhman and Uriel Levy

Department of Applied Physics, The Benin School of Engineering and Computer Science, The Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Jerusalem, 91904, Israel

In recent years, following the miniaturization and integration of passive and active nanophotonic devices, thermal characterization of such devices at the nanoscale is becoming a task of crucial importance. The Scanning Thermal Microscopy (SThM) is a natural candidate for performing this task. However, it turns out that the SThM capability to precisely map the temperature of a photonic sample in the presence of light interacting with the sample is limited. This is because of the significant absorption of light by the SThM probe. As a result, the temperature of the SThM probe increases and a significant electrical signal which is directly proportional to the light intensity is obtained. As such, instead of measuring the temperature of the sample, one may measure the light intensity profile. While this is certainly a limitation in the context of thermal characterization of nanophotonic devices, this very property provides a new opportunity for optical near field characterization. Here we demonstrate numerically and experimentally the optical near field measurements of nanophotonic devices using a SThM probe. The system is characterized using several sets of samples with different properties and various wavelengths of operation. Our measurements indicate that the light absorption by the probe is far more significant than the light induced heat generation in the sample. The simplicity of the SThM system which eliminates the need for complex optical measurement setups together with its broadband wavelength of operation makes this approach an attractive alternative to the more conventional aperture and apertureless NSOM approaches.

 

 

 

[513] SUPER-RESOLUTION MICROSCOPY BY ANTIBUNCHING ASSISTED LOCALIZATION

 

Ron Tenne¹, Yonatan Israel¹, Yaron Silberberg¹, Dan Oron²

 

	1 Weizmann Institute of Science; Herzl 234
	2 Department of Physics of Complex Systems; Weizmann Institute of Science

 

 

Super-Resolution Microscopy by Antibunching Assisted Localization

 

Ron Tenne¹, Yonatan Israel¹, Yaron Silberberg¹ and Dan Oron¹

 

1 Department of Physics of Complex Systems, Weizmann Institute of Science, 76100 Rehovot, Israel

 

Super resolution microscopy, the ability to resolve objects smaller than the wavelength of visible light, has developed from a research concept into applicable methods regularly used in biology nowadays. While a variety of methods have been well developed none produces a general route to acquire a super-resolved image. In particular only a handful of methods can incorporate photo-stable quantum dots (QDs) as contrast agents. Here we present ongoing work towards implementing a method relying on the quantum nature of a single quantum dot fluorescence in order to localize them in space and generate a super-resolved image.

 

A Hanbury-Brown and Twiss setup is employed to locate periods in which only a one out of a few blinking QDs is fluorescing. These episodes are then used to localize the position of the emitter with an accuracy of a tenth of the wavelength. Preliminary results showing the localization of two QDs as well as future outlook and obstacles will be presented.

 

 

NANOSCUPTURED THIN FILMS BASED SERS BIOSENSOR: HIGHLY SENSITIVE & SPECIFIC DETECTION OF E. COLI

 

Sachin K. Srivastava ^*,1a,1b,2,#, Hilla Ben Hamo ^1c, Ariel Kushmaro ^1b,1c,2, Robert S. Marks ^1b,1c,2   Christoph Grüner ³, Bernd Rauschenbach ^3,4 and Ibrahim Abdulhalim ^1a,1b,2

 

1a.Department of Electro optic Engineering, –

1 b. Ilse Katz Institute for Nanoscale Sciences and Technology, –

1c. The Avram and Stella Goldstein-Goren Department of Biotechnology Engineering,-

– Ben Gurion University of the Negev, Beer Sheva-84105, Israel

2. NTU-HUJ-BGU CREATE Programme, School of Materials Science and Engineering, Nanyang Technological University, 637722, Singapore,
3. Leibniz Institute of Surface Modification, Permoserstrasse 15, 04318 Leipzig
4. University Leipzig, Institute for Experimental Physics II, Linnéstr.5, 04307 Leipzig, Germany

* E-mail:sksrivastava@ntu.edu.sg,   #Present affiliation

 

Nanosculptured thin films (nSTFs) of silver (300 nm height and 30 % porosity over Si substrates) were used to develop a surface enhanced Raman spectroscopy (SERS) based nanobiosensor for very specific detection of E. coli up to the concentration levels of single bacterium [1]. These are columnar films of metal. The sensor chip was fabricated by immobilizing T4- bacteriophages. The sensor was tested for two strains of E. coli (RFM443 (E. coli B) and XLMRF (E. coli μX)] and 3 other gram negative bacteria C. violaceum (CV026), P. dentrificans and P. aeruginosa as negative control experiments.

 

(c)

Fig. 1 Sensor Response at1077cm^-1 Raman shift of the sensor chip for all the bacteria

 

Fig. 1 shows the difference of the SERS enhancement of the sample on the sensor to that from the bare sensor chip, (I_sample – I_sensor) for varying bacterial concentrations. It is observed that the sensor response does not change with any increase in concentrations for other kinds of bacteria, while that shows an increase sample solutions of both kinds of E. coli. The sensor utilizes only 10 μl from a solution of 150 cfu/ml concentration, which means detection up to single bacterium.  

 

 

References

1. Srivastava et al., Analyst 140, 3201-3209 (2015).

 

 

 

STRONG COUPLING OF PHOSPHORESCENT PTOEP MOLECULES IN METALLIC MICROCAVITIES

Roli Verma, Tal Schwartz*
School of Chemistry, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Tel Aviv,
6997801, Israel
*talschwartz@post.tau.ac.il
Strong coupling of organic molecules with optical microcavities can result in the formation of hybrid
light matter state, named polaritons, which may modify the molecular photophysical properties, as was
recently demonstrated [1,2]. Herein, we present strong coupling of triplet emitter platinum
octaethylporphyrines (PtOEP), where strong coupling may provide a novel mechanism for controlling
intersystem crossing. To realize these states, PtOEP molecules (doped into a PMMA host matrix,
~120nm thick layer) has been sandwiched nm between two silver mirrors which form an optical cavity.
Three absorption band of PtOEP molecule is shown in fig. 1(a) (black curve). The photoluminescence
properties of PtOEP molecules are also shown in fig. 1(a) where green curve and blue curve corresponds
to phosphorescence and fluorescence band respectively [3]. When the molecular Q-band excitation
(around 535nm) is coupled to the cavity, the formation of three polariton states is clearly seen in the
transmission (fig. 1b, black curve). Moreover, the photoluminescence in cavity (red curve in fig.1b)
matches with transmission of cavity. Moreover, the coupled system shows a typical polariton angleresolved
dispersion (inset in fig. 1b), proving that our system indeed operates in the strong coupling
regime, with a Rabi splitting energy of 104 meV between the upper and middle polariton branches, and
172meV between the middle and lower polariton branches. We expect that time-resolved spectroscopic
studies, which are currently underway, will reveal a modified intersystem crossing rate and modified
triplet occupation, with important applications in organic electronics and photochemical reactions.
Figure 1 (a) absorption (black solid), emission (green solid and blue solid) and Excitation (red solid) of bare molecule (b) cavity
transmission (black solid) and emission (red solid) and inset is the dispersion diagram of coupled system
1. J. A. Hutchison et al., Angew. Chem. Int. Ed. 51, 1592 (2012).
2. T. Schwartz et. al., ChemPhyChem 14, 125 (2013).
3. S. Kena-Cohen et. at., Phy. Rev. B, 075202 (2007).