Asaf Shahmoon

Self Assembly of Nano Metric Metallic Particles for Realization of Photonic and Electronic Nano Transistors

In this paper, we present the self assembly procedure as well as experimental results of a novel method for constructing well defined arrangements of self assembly metallic nano particles into sophisticated nano structures. The self assembly concept is based on focused ion beam (FIB) technology, where metallic nano particles are self assembled due to implantation of positive gallium ions into the insulating material (e.g., silica as in silicon on insulator wafers) that acts as intermediary layer between the substrate and the negatively charge metallic nanoparticles.

Sub-Micron Particle Based Structures as Reconfigurable Photonic Devices Controllable by External Photonic and Magnetic Fields

In this paper we present the configurations of two nanometer scale structures—one of them optically controllable and the second one magnetically controllable. The first involves an array of nanoparticles that are made up of two layers (i.e., Au on top of a Si layer). The device may exhibits a wide range of plasmonic resonance according to external photonic radiation. The second type of device involves the usage of sub micron superparamagnetic particles located on a suitable structuring grid, that according to the angle of the external magnetic field allows control of the length of the structuring grid and therefore control the diffraction order of each wavelength.

Design and Fabrication of 1 × 2 Nanophotonic Switch

We present the design and the fabrication of a novel 1×2 nanophotonic switch. The switch is a photonic T-junction in which a gold nano particle is being positioned in the junction using the tip of an atomic force microscope (AFM). The novelty of this 1×2 switch is related to its ability to control the direction of wave that propagates along a photonic structure. The selectivity of the direction is determined by a gold nanoparticle having dimension of a few tens of nanometer. This particle can be shifted. The shift of the gold nano particle can be achieved by applying voltage or by illuminating it with a light source. The shifts of the particle, inside the air gap, direct the input beam ones to the left output of the junction and once to its right output. Three types of simulations have been done in order to realize the photonic T-junction, and they are as follows: photonic crystal structures, waveguide made out of PMMA, and a silicon waveguide.

All-optical nano modulator, sensor, wavelength converter, logic gate, and flip flop based on a manipulated gold nanoparticle

We developed a device in which one can shift and control the position of a gold nanoparticle by using special type of optical tweezers realized by guiding and confining light in a nanosize void structure in which the nanoparticle is placed. The nanosize void is positioned inside a multimode interference (MMI) region of a silicon waveguide. The coupling of light from two opposite sides of the optical device generates standing interference waves in the MMI region. The relative phase between the two coupled beams is controllable and therefore also the position of the fringes of the standing waves. Evanescent tails coming from the guided standing waves interfere in the void and allow control the position of the trapped nanoparticle. A nanoparticle with diameter of 30 nm was experimentally implanted in the void. The particle was trapped by one of the high intensity evanescent fringes. Changing the relative phase between the two inputs to the chip allowed us experimentally to modify the location of the fringes and the position of the particle (similarly to what happens in optical tweezers). This experimentally demonstrated capability may be useful for all-optical nano modulators, sensors, wavelength converters, logic gates and even a state machine (e.g. a flip flop).

All-optical integrated micro logic gate

In this paper we present a novel approach for realizing an integrated all-optical logic gate. The basic principle is based upon stimulated emission process generated in an active gain medium while special interferometric photonic wave-guiding structure allows the realization of an integrated micro scale device. The operation rate of the proposed device structure can theoretically reach tens of Tera-Hertz.

Neural networks within multi-core optic fibers.

Hardware implementation of artificial neural networks facilitates real-time parallel processing of massive data sets. Optical neural networks offer low-volume 3D connectivity together with large bandwidth and minimal heat production in contrast to electronic implementation. Here, we present a conceptual design for in-fiber optical neural networks. Neurons and synapses are realized as individual silica cores in a multi-core fiber. Optical signals are transferred transversely between cores by means of optical coupling. Pump driven amplification in erbium-doped cores mimics synaptic interactions. We simulated three-layered feed-forward neural networks and explored their capabilities. Simulations suggest that networks can differentiate between given inputs depending on specific configurations of amplification; this implies classification and learning capabilities. Finally, we tested experimentally our basic neuronal elements using fibers, couplers, and amplifiers, and demonstrated that this configuration implements a neuron-like function. Therefore, devices similar to our proposed multi-core fiber could potentially serve as building blocks for future large-scale small-volume optical artificial neural networks.

In vivo minimally invasive interstitial multi-functional microendoscopy

Developing minimally invasive methodologies for imaging of internal organs is an emerging field in the biomedical examination research. This paper introduces a new multi-functional microendoscope device capable of imaging of internal organs with a minimal invasive intervention. In addition, the developed microendoscope can also be employed as a monitoring device for measuring local hemoglobin concentration in blood stream when administrated into a blood artery. The microendoscope device has a total external diameter of only 200 μm and can provide high imaging resolution capability of more than 5,000 pixels. The device can detect features with a spatial resolution of less than 1 μm. The microendoscope has been tested both in-vitro as well as in-vivo in rats presenting a promising and powerful tool as a high resolution and minimally invasive imaging facility suitable for previously unreachable clinical modalities.

“Beating speckles” via electrically-induced vibrations of Au nanorods embedded in sol-gel

Generation of macroscopic phenomena through manipulating nano-scale properties of materials is among the most fundamental goals of nanotechnology research. We demonstrate cooperative “speckle beats” induced through electric-field modulation of gold (Au) nanorods embedded in a transparent sol-gel host. Specifically, we show that placing the Au nanorod/sol-gel matrix in an alternating current (AC) field gives rise to dramatic modulation of incident light scattered from the material. The speckle light patterns take form of “beats”, for which the amplitude and frequency are directly correlated with the voltage and frequency, respectively, of the applied AC field. The data indicate that the speckle beats arise from localized vibrations of the gel-embedded Au nanorods, induced through the interactions between the AC field and the electrostatically-charged nanorods. This phenomenon opens the way for new means of investigating nanoparticles in constrained environments. Applications in electro-optical devices, such as optical modulators, movable lenses, and others are also envisaged.

Micro mirrors based coupling of light to multi-core fiber realizing in-fiber photonic neural network processor

Hardware implementation of artificial neural networks facilitates real-time parallel processing of massive data sets. Optical neural networks offer low-volume 3D connectivity together with large bandwidth and minimal heat production in contrast to electronic implementation. Here, we present a DMD based approaches to realize energetically efficient light coupling into a multi-core fiber realizing a unique design for in-fiber optical neural networks. Neurons and synapses are realized as individual cores in a multi-core fiber. Optical signals are transferred transversely between cores by means of optical coupling. Pump driven amplification in Erbium-doped cores mimics synaptic interactions. In order to dynamically and efficiently couple light into the multi-core fiber a DMD based micro mirror device is used to perform proper beam shaping operation. The beam shaping reshapes the light into a large set of points in space matching the positions of the required cores in the entrance plane to the multi-core fiber.

Non-labeled lensless micro-endoscopic approach for cellular imaging through highly scattering media

We describe an imaging approach based on an optical setup made up of a miniature, lensless, minimally invasive endoscope scanning a sample and matching post processing techniques that enable enhanced imaging capabilities. The two main scopes of this article are that this approach enables imaging beyond highly scattering medium and increases the resolution and signal to noise levels reaching single cell imaging. Our approach has more advantages over ordinary endoscope setups and other imaging techniques. It is not mechanically limited by a lens, the stable but flexible fiber can acquire images over long time periods (unlike current imaging methods such as OCT etc.), and the imaging can be obtained at a certain working distance above the surface, without interference to the imaged object. Fast overlapping scans enlarge the region of interest, enhance signal to noise levels and can also accommodate post-processing, super-resolution algorithms. Here we present that due to the setup properties, the overlapping scans also lead to dramatic enhancement of non-scattered signal to scattered noise. This enables imaging through highly scattering medium. We discuss results obtained from in vitro investigation of weak signals of ARPE cells, rat retina, and scattered signals from polydimethylsiloxane (PDMS) microchannels filled with hemoglobin and covered by intralipids consequently mimicking blood capillaries and the epidermis of human skin. The development of minimally invasive procedures and methodologies for imaging through scattering medium such as tissues can vastly enhance biomedical diagnostic capabilities for imaging internal organs. We thereby propose that our method may be used for such tasks in vivo.