Hossin Abdeldayem

An all-optical picosecond switch in polydiacetylene

A polydiacetylene derivative of 2-methyl-4-nitroaniline (PDAMNA) showed a picosecond switching property. This phenomenon was demonstrated by waveguiding a cw He–Ne laser collinearly with a mode-locked picosecond Nd:YAG laser at 532 nm through a hollow fiber coated on the inside with a thin film of PDAMNA. The Z-scan investigations of PDAMNA thin films revealed that the PDAMNA system is a three-level system and the switching is caused by excited state absorption of the He–Ne beam.

Edge enhancement and edge-enhanced correlation with photorefractive polymers

We demonstrate a simple all-optical realization of programmable edge enhancement and edge-enhanced correlation using novel photorefractive polymers. We show that the higher non-Bragg order in a two-beam coupling scheme contains the edge enhancement of the object when placed in the path of one of the incident beams. Also, this arrangement provides a scheme for writing joint transform correlation dynamic holograms, which can be read by a third beam. The correlation is edge enhanced, and the correlation peak increases with the applied bias voltage. Numerical results without and with beam fanning are presented. Theoretical predictions are reconciled with experimental results.

Optical computing: need and challenge

Focusing on the reality and promise of optical computing.

Photoinduced Optical and Electrical High-Voltage Pulsations and Pattern Formation in Photorefractive Crystals

We review our results on conversion of CW laser Ar-ion beam power into pulsating multi-channel outputs: optical, electric and piezoelectric with simultaneous dynamic pattern formation. We show, that electrical pulsations generate high-voltage signals that may be used as a driving voltage for the conventional electro-optical modulator. We have also demonstrated the possibility of synchronization of two optical pulsators, through regulated optical coupling in a photorefractive LiNbO3 crystal. Spatial distribution of scattered light is self-organized in different patterns (hexagonal and cross-type).

Recent Advances in Photonic Devices for Optical Super Computing

The twentieth century has been the era of semiconductor materials and electronic technology while this millennium is expected to be the age of photonic materials and optical technology. Optical technology has led to countless optical devices that have become indispensable in our daily lives in storage area networks (SANs) [1], parallel processing [2,3], optical switches [4,5], all-optical data networks [6], holographic storage devices [7] and biometric devices at airports [8].

Contamination and radiation effects on spaceflight laser systems

Space Lasers are vital tools for NASAs space missions and military applications. Although, lasers are highly reliable on the ground, several past space laser missions proved to be short-lived and unreliable. In this communication, we are shedding more light on the contamination and radiation issues, which are the most common causes for optical damages and laser failures in space. At first, we will present results based on the study of liquids and subsequently correlate these results to the particulates of the laser system environment. We present a model explaining how the laser beam traps contaminants against the optical surfaces and cause optical damages and the role of gravity in the process. We also report the results of the second harmonic generation efficiency for nonlinear optical crystals irradiated with high-energy beams of protons. In addition, we are proposing to employ the technique of adsorption to minimize the presence of adsorbing molecules present in the laser compartment.

Simulation of wave mixing in photorefractive polymers

A numerical simulation model of two-beam interaction in photorefractive polymers is presented. Higher diffraction orders and beam fanning are included in the model. The simulation results were found to agree precisely with theoretical predictions and experiments. Edge enhancement of images in a two-beam coupling geometry is predicted.

Photoinduced optical and electrical pulsations and pattern formation in photorefractive crystals

We have observed the conversion of CW laser Ar-ion beam power into pulsating multi-channel outputs: optical, electric and piezoelectric with simultaneous dynamic pattern formation. Frequencies of multi-channel pulsations have characteristic sigmoidal dependence (with threshold) on laser intensity. We have also demonstrated the possibility of synchronization of two optical pulsators, through regulated optical coupling in a photorefractive LiNbO3 crystal. Spatial distribution of scattered light is selforganized in different patterns (hexagonal and cross-type)

Holographic recording in polymeric materials with diffusional amplification

The volume holographic gratings in polymer materials are promising candidates for spectrally selective optical elements, dense data storage, optical communication, and spectral selective imaging. Recently new application of volume reflection-type grating for fast all-optical temporal/spatial light modulators was suggested. Spatial modulation of diffracted red beam by green laser was demonstrated. We also suggest and analyze theoretical model for material with diffusional amplification for different modes of recording: (1) Fast recording with following annealing; (2) Slow recording (real-time grating).

Fast all-optical spatial-temporal light modulator

We suggest to use modulation of distributed feedback in the volume reflection type diffractive periodic structures for the fast all-optical spatial-temporal light modulators. Different types of periodic structures are discussed: cholesteric liquid crystals, static and dynamic reflection gratings in the photorefractive crystals and photopolymers.