Welcome to Applied Nano-Photonics Group 

Our research activities are oriented towards imaging methods and devices for industrial, biomedical and environmental optical applications. Our research is focused on three main activities:

• Sub-nm 3D Imaging and axial position tracking: two prototypes have been developed, the first allowing video rate 3D imaging of moving samples with nm scale resolution, and the second allowing single point, very high speed, axial motion tracking and vibrometry with sub-nm resolution and max inter-sampling axial position change of 30µm.

• Plasmonic nano-photonic structures for biosensing based on the enhancement of the        

        electromagnetic field near the sensor-analyte interface.

•  Nanophotonic liquid crystal devices incorporated into biomedical optical imaging systems and diagnostic devices such as spectro-polarimetric imaging and full field optical coherence tomography, diagnosis with THz polarimetry, intraocular pressure measurement and skin cancer diagnosis.

• Simulations to discover new fields such as THz polarimetric imaging, smart windows for in-building energy management using photonic and plasmonic structures.

 

Plasmonic nanostructures for biosensing:

 

In this activity we use surface Plasmon resonance in Kretschmann configuration both in the angular and the spectral modes, Fluorescence microscopy and Raman scattering, see figure below:

 

 

 

 

 

 

 

 

 

 

We have recently demonstrated surface Plasmon resonance (SPR) sensor with enhanced sensitivity by adding a nm-thick dielectric layer with high dielectric constant to the metal (see Amit Lahav et.al., Optics Letter 2008).

 

 

 

 

 

 

 

 

 

 

A special SPR imaging approach was developed using a diverging beam and the fast Radon transform for line detection. This approach improves the precision of the sensor and allows multichannel sensing (Alina Karabchevsky et.al. Sensors and Actuators B 2011, J. Nanophotonics 2011). Small concentration of BPA in water was detected (~1ng/L). See figure below.

 

 

 

 

 

 

 

 

Using this same methodology we have demonstrated recently two important sensors:

(1) sensor based on the total internal reflection in which the angular edge is converted to a dip using a periodic stack of quarter wave layers with possibility to obtain unlimited figure of merit by increasing the number of periods (Watad et.al., Optics Letters 2015).

 

 

 

 

 

 

 

 

 

 

 

(2) SPR based self-referenced sensor with ultrahigh penetration depth suitable for detecting cells and bacteria (Isaacs et. al, APL 2015).

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Another interesting self-referenced sensor concept is based on thin dielectric grating on top of thin metal layer which allows the excitation of two plasmons at the two metal boundaries (AbuToama, Optics Express 2015, IEEE JSTQE 2016).

 

 

 

 

 

 

 

 

 

 

 

 

An ultrahigh electromagnetic field enhancement near metallic nano-features was discovered when the LSPR excitation is achieved via extended SPR.  It was demonstrated both theoretically and experimentally using SEF (Li et. al. J, Phys. chem. C 2015).

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Another type of nano-photonic structures being investigated in our group is the metallic sculptured thin films (STFs) which are made of nano-columns of metal with controlled porosity and orientation.

 

 

 

 

 

 

 

 

 

 

 

As nano-rods like structures the surface Plasmon wave is localized near their tips and hence the electromagnetic wave density is enhanced. As a result we have demonstrated recently the enhancement of fluorescence signal from fluorophores near these structures (see Abdulhalim et.al., Appl.Phys.Lett., 2009) and used it for detecting bacteria in water as shown in the figure below.

 

 

 

 

 

 

 

 

 

Raman signal enhancement is another promising technique we are working on for sensing because it provides specificity, that is it can tell also the type of the pollutant not only its concentration. (Atef Shalabney et.al., J. Nanophotonics 2013, Sachin K. Srivastava et.al. Small 2013). See figure below:

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Since the STFs are porous then when used as SPR sensors in the Kretschmann configuration they exhibit enhanced sensitivity due to the increase of the surface to volume ratio (see Atef Shalabney et.al., J. Photonics and Nanostructures 2009, Sensors and Actuators B 2011).

 

 

 

 

 

 

 

 

 

 

 

Another promising structure for sensing is the use of resonant enhanced transmission through nano-holes in metals. Presently we are optimizing one-dimensional array of metal nanoslits for Biosensing in water (see Alina Karabchevsky et.al., J. Photonics and Nanostructures, 2009). Our main goal in these studies is to come up with a highly sensitive and reliable sensor that can be easily integrated in water to monitor small quantities of pollutants. In parallel to the fundamental studies that we are performing, we also design and build prototype sensors that will be used in a true water purifying system.

 

 

 

 

 

 

 

 

 

 

Recently (Olga Krasnykov et.al., Optics Communications 2010) we have increased the penetration depth inside the analyte by using infrared wavelengths in order to increase the sensitivity and be able to detect large bioentities such as cells.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The self-referenced action of this sensor was demonstrated recently by Srivastava et.al, Optics Letter 2015.

 

 

 

 

 

 

 

 

 

 

 

 

 

Nanophotonic liquid crystal devices for biomedical imaging:

 

In this activity liquid crystals (LCs) are combined with nanostructures in order to come up with miniature devices to control the optical properties of the light such as producing tunable filters and polarizations controllers. These devices can be controlled with a small voltage in a high speed. Recently we have combined such novel LC devices into spectropolarimetric skin imaging system being evaluated at Soroka hospital for skin cancer diagnosis. In the figure below a wide dynamic range filter is demonstrate using a novel concept (O. Aharon et.al., Optics Express 2009, Optics Letters 2009, J. Biomedical Optics 2011).

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Polarization control devices were also developed and integrated into the same system.  The idea is by grabbing images at many polarization states and many wavelengths the information content on the tissue structure is enhanced and the reliability of the devices increases (Avner Safrani et.al., Optics Letters 2009, J. Biomedical Optics 2010, Graham et.al. J. Biomedical Optics 2013).

 

 

 

 

 

 

 

 

 

 

 

In an attempt to perform polarimetric measurements at many wavelengths simultaneously we have developed recently a tunable achromatic waveplate over wide band composed of two LC retarders (AbuLeil and Abdulhalim, Optics Letters, 2015).

 

In parallel we are developing methodologies to precisely characterize the LC devices (Marwan Abu Leil et.al., Applied Optics 2014) and to improve their performance such as the polarization independent tunable Fabry Perot filter developed by Sivan Issac (Optical Engineering 2014) and the tunable achromatic LC waveplate by Marwan Abu Leil (Optics Letter, 2014).

 

 

 

 

 

 

 

 

 

 

 

 

In combining LC with nano-porous Si photonic crystal structure we are trying to create a narrow band tunable filter.  Recently we have discovered that the molecules get ordered within the cylindrical nano-pores in a special way.  Applying a voltage to the composite caused the filter peak to split into two polarization dependent peaks, thus indicating that the composite is biaxial (Shahar Mor et.al., Applied Physics Letters 2010).  In the figure below: (a) Atomic force microscope image of the top layer of the P-Si 1D structure used, (b) schematic cross section view of the layered structure where AL stands for alignment layer; (c) and (d) are 20x polarized microscope images of the two samples, showing their corresponding filter color of green and red; (e)-(h) schematic drawings to illustrate some of the LC configurations inside the pores showing the UA, homeotropic, PR and ER configurations respectively.

 

 

 

 

 

 

 

 

 

 

 

 

 

In the same context we have prepared PbS film using the oblique incidence evaporation techniques and surprisingly we obtained highly porous anisotropic meso structure which acted both as an alignment layer of LCs, as a polarizer, anti-reflective and absorber (Chaudhary et.al., Nanotechnology 2015).  Surprisingly also the normal incidence evaporated films showed poros network and we demonstrated it as a sensor (Chaudhary et.al., to be published 2016).

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Recently we have discovered the possibility of photoalignment of liquid crystals on nano dimensional chalcogenide glass films (Miri Gelbaor, Appl.Phys.Lett. 2011) and we have shown that it is a result of the photoinduced anisotropy in these materials even for such thin films as thin as 20nm (I. Abdulhalim et.al., OMEX, 2011).

 

 

 

 

 

 

 

 

 

 

 

 

 

 

In addition the ND chalcogenides films acted as photosensors for optically addressed light modulation (OASLM), a device useful for night goggles, optical computing and holographic imaging (Gelbaor et.al, OL 2014).

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Another important activity involves the incorporation of liquid crystal devices into full field optical coherence tomography system. With the assistance of a single retarder incorporated into FF-OCT system based on the Linnik microscope, Ph.D student Avner Safrani has succeeded to obtain high resolution 3D images of cell nuclei both in the axial and the lateral directions (A. Safrani et.al., Appl.Optics 2011, Optics Letters, 2012).

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Recently this system was improved to give nano-precision measurements useful for surface profiling and monitoring the fabrication processes of nanoelectronic devices using 3-channelled parallel phase interferometric imaging (Safrani and Abdulhalim, OL 2014).

 

 

 

 

 

 

 

 

 

 

 

 

 

 

This concept was developed further recently to overcome the phase unwrapping problem using two wavelengths approach and demonstrated to image pillars of few microns height without any scanning (Safrani and Abdulhalim, Optics Letters 2015).

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Recently we have fabricated a transmissive annular spatial light modulator (ASLM) and showed that it is possible to use it to enhance the performance of optical imaging systems such as extended depth of focus (EDOF), tunable focal length, beam shaping and other (Iftach Klapp et.al. Optics Letter 2014, Asi Solodar et.al., Optics Communications 2014).

 

 

 

 

 

 

 

 

 

 

 

 

One important activity is the development of night goggles based on LC-OASLM when the photosensor is in the SWIR.  Using an InGaAs photodiodes array stacked with LC layer we have demonstrated recently the initial device (Solodar et.al. APL 2016).

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Simulations works to discover new diagnostic methodologies, devices and energy management in buildings

 

In this activity we perform rigorous simulations using COMSOL multuphysics, Monte-Carlo simulations and other rigorous electromagnetic simulations of nanophotonic and nanoplasmonic structures.  A nanophotonic structure for smart window application was designed based on nanoapertures in VO2 film (Liu et.al., Optics Express 2015).

 

 

 

 

 

 

 

 

 

 

 

In this activity we perform rigorous simulations using COMSOL multuphysics, Monte-Carlo simulations and other rigorous electromagnetic simulations of nanophotonic and nanoplasmonic structures.  A nanophotonic structure for smart window application was designed based on nanoapertures in VO2 film (Liu et.al., Optics Express 2015).