Elsa Garmire

Theory of bistability in nonlinear distributed feedback structures

We show that optical bistability can occur in a distributed feedback structure with an intensity‐dependent refractive index. Analytical expressions for the transmissivity are obtained and a comparison with Fabry‐Perot‐type devices is presented.

Resonant optical nonlinearities in semiconductors

Semiconductors provide some of the most promising materials for nonlinear optics, because of large resonant nonlinearities, control of recombination time (from milliseconds to femtoseconds), well-developed fabrication technologies, and compatibility with other optoelectronic devices. The paper reviews some of the concepts and results that have come from the study of nonlinear optics in semiconductors. The emphasis is on nonlinear absorption and the refractive index that arises from the photo-induced excitation of free carriers. Mechanisms described include state-filling, carrier transport, and photorefractivity. Devices include optical bistability, reflective asymmetric Fabry-Perot all-optical absorptive switches, optically addressed spatial light modulators, and real-time holography. The papers approach is to provide a basic engineering understanding of the principles, some of the historical details, and a snapshot of the state of the field today.

Photorefractivity at 1.5 μm in CdTe:V

We have for the first time demonstrated two‐beam coupling energy transfer at a wavelength of 1.5 μm. Beam coupling gain coefficients of 0.6 cm−1 have been obtained in vanadium ‐doped CdTe with only 5 mW/cm2 incident intensity. These gain coefficients exceed typical gain coefficients in GaAs at 1.06 μm wavelength by 50%. In preliminary measurements using the moving grating technique, we have measured a gain coefficient of 2.4 cm−1. Through adjustment of the doping level, CdTe:V can be used as a sensitive photorefractive material through the 0.9–1.5 μm spectral range.

Nonlinear Optics in Semiconductors

The dream of the all‐optical processing of information has motivated efforts over the past decade to create sensitive semiconductors that have large optical nonlinearities. Semiconductors have been the medium of choice in part because a well‐developed materials technology has already been built around them. One can design semiconductor structures easily and predict their performance accurately.

Temporal/spatial optical CDMA networks-design, demonstration, and comparison with temporal networks

The design and experimental results for a temporal/spatial (T/S) noncoherent optical code-division multiple access (CDMA), based on matrix codes, using a breadboard of passive multimode fiber-optic couplers and delay lines, is presented. It is shown that a T/S CDMA network allows for shorter bit times, given a set laser pulse width, compared to a temporal CDMA network. Also, T/S codes result in a reduction of autocorrelation sidelobes and cross-correlation peaks, and the T/S network has lower losses. It is also shown that the couplers are critical components in maintaining code integrity.<<ETX>>

Incoherent mirrorless bistable optical devices

A new class of bistable optical devices is described which do not require resonators or single‐mode lasers. Optical bistability was demonstrated using a LiNbO3 electro‐optic modulator and a multimode laser.

Photonics: Linear and Nonlinear Interactions of Laser Light and Matter

Topics in Photonics.- Properties and Description of Light.- Linear Interactions between Light and Matter.- Nonlinear Interactions of Light and Matter without Absorption.- Nonlinear Interactions of Light and Matter with Absorption.- Lasers.- Nonlinear Optical Spectroscopy.- References.

Transient response of hybrid bistable optical devices

The response of a hybrid bistable optical device to step inputs of light was studied experimentally. The results confirm theoretical predictions concerning the dependence of switching time on the applied light increment. For the first time the phenomenon of ’’critical slowing down’’ is observed directly.

Flexible infrared waveguides for high-power transmission

This paper gives a comparison of theory with experimental results for the transmission of flexible infrared waveguides fabricated from commercially available aluminum sheet. From this analysis, design equations are generated, which may be used to predict the losses of FIT waveguides in useful geometries.

Propagation of infrared light in flexible hollow waveguides

Designs are described for flexible hollow waveguides with low ir loss over distances on the order of 1 m. Transmission losses at 10.6 microm are calculated, and the effect of bends and twists is discussed. A hollow combination metal-dielectric-walled rectangular waveguide is proposed that can have transmission as high as 95% for a 1-m length, while bent with a 1-m radius of curvature.