Ofer Limon

All-optical nano modulator on a silicon chip.

We present an all-optical modulator realized on a silicon chip. The proposed modulator has nano scale dimensions and a high extinction ratio. Its operation principle is based on a spatially non-uniform variation of the absorption of a miniaturized, silicon waveguide - based Mach-Zehnder interferometer (MZI). The absorption variation is obtained by illuminating the MZI with visible light. Our modulator may be used as an interfacing link between microelectronic processing circuits and optical information transmission links. We provide details on the fabrication and the experimental characterization of the suggested device. Since the operation principle is not based on a high Finesse resonator, the modulator is less sensitive to wavelength changes and its operation rate is not connected to the time required for the optical response to reach steady state but rather to material related effects.

Transverse resolution improvement using rotating-grating time-multiplexing approach

The ability to improve the limited resolving power of optical imaging systems while approaching the theoretical diffraction limit has been an attractive discipline with growing interest over the last years due to its benefits in many applied optics systems. This paper presents a new approach to achieve transverse superresolution in far-field imaging systems, with direct application in both digital microscopy and digital holographic microscopy. Theoretical analysis and computer simulations show the validity of the presented approach.

Nanophotonic interferometer realizing all-optical exclusive or gate on a silicon chip

We present an all optical approach allowing the realization of microscale logic exclusive or (XOR) gate based on special interferometer configuration. The operation device includes two close optical waveguides realized on a silicon chip. A thin metallic layer of a few nanometers that separates the two waveguides causes a relative phase shift of between them. The structure performs interference of the two input beams while demonstrating XOR logic gate operation at the amplitude of the resulted output. The logic operation is realized after small propagation distance of <1.8 µm.

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.

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).

Metal-oxide semiconductor, field effect transistor-based microscale electro-optical multimode interference modulator on a silicon chip

A new approach allows the realization of an electro-optical modulator or a transistor that is integrated on a silicon chip. The operation principle includes the realization of optical multimode interference (MMI) as the operation core of an electro-optical metal-oxide-semiconductor (MOS) field effect transistor (FET). Externally applied voltage generates a depletion region as well as layer of inversion which is full with free carriers. The free carriers vary the relative phase shift as well as the attenuation of one arm of the interferometer due to the plasma dispersion effect in silicon. This variation allows breaking the balance of the mode conversion and results with amplitude modulation in the output of the MMI region. The device does not have high finesse resonance and yet its overall length is only about 18 μm.

Miniaturized Bragg modulator on a silicon chip

We present a new design of a miniaturized modulator on a silicon chip. The modulation principle is based upon the plasma dispersion effect in which free electrons affect the real and the imaginary part of the refractive index. The novelty of the modulation configuration is related to its periodically patterned electrodes due to which the applied voltage generates axially periodic change in index of refraction. This results with the generation of an effective Bragg filter. Such filter allows having shorter device with the same extinction ratio or having a device with the same length but with improved modulation contrast.

Electronic devices based upon Germanium nano-crystals with durability to strong neutron irradiation

In this paper we present the preliminary experimental characterization of electronic devices based upon Germanium nano-crystals (nc-Ge) embedded in thick SiO2 films grown on a Si substrate. The samples were prepared using Ge ion implantation followed by thermal annealing. Typical diameter of the nc-Ge is shown to be in the range of 4- 10nm. Gold (Au) contacts were deposited on the top of the oxide surface allowing measurements of the electronic properties. We present preliminary experimental results of electronic properties of the nc-Ge based devices including current-voltage (I-V) and capacitance-voltage (C-V) curves of the nano-devices while illuminated by white light and an external laser at a wavelength of 532nm for various levels of intensity. The characterization curves were also obtained at different temperatures. The proposed technology of devices based on nc-Ge was proven to be insensitive to high doses of irradiation by neutrons in a research nuclear reactor, which suggests that these nc-Ge devices can be used under extreme working conditions such as strong cosmic radiation appearing in outer space.

Clinical trials of interference-based extended depth of focus intra ocular lens design

In this paper we present the clinical trials performed with intra ocular lens (IOL) design having interference based extended depth of focus. The purpose of such IOL design is to allow cataract patients avoid using glasses after doing their surgery.