J. M. Glinski

All-optical reflectivity tuning and logic gating in a GaAs/AlAs periodic layered structure

The optical nonlinearity of a GaAs/AlAs periodic layered structure was experimentally investigated for the first time. The shift of the reflectivity peak with increasing intensity was observed. A reflectivity contrast of about 10:1 was obtained by varying the incident intensity. Hysteresis loops due to the response delay of both the electronic and the thermal nonlinearity were observed. All‐optical logic operations were also demonstrated. A further improvement of the structure may lead to a new type of optical bistable device.

Electro‐optical switching in a GaAs multiple quantum well directional coupler

Theoretical and experimental results are reported on electro‐optical switching in a GaAs‐based multiple quantum well coupled planar nonlinear optical directional coupler. It is shown that a careful selection of the wavelength of operation can lead to an efficient, practically constant loss, low electric field controlled transfer of light energy from one slab waveguide to the other. The quantum‐confined Stark effect in the multiple quantum well coupling layer is employed as the switching mechanism. Results are compared with those achieved with nonlinear all‐optical switching in the same structure. It is believed that this is the first semiconductor ΔK switch.

Multiple quantum well coupling element with losses

A nonlinear directional coupling element consisting of a GaAs‐based multiple quantum well (MQW) heterostructure sandwiched between two slab optical waveguides is analyzed numerically with optical absorption losses in the MQW included. Optical waveguides are designed to be made of lossless AlGaAs slabs of an appropriate composition corresponding to the wavelength of operation. Calculations indicate an improvement in the element’s overall propagation attenuation by about two orders of magnitude when compared to previous results dealing directly with MQW optical waveguides. Promising element performance characteristics are reported.

Electro‐optic switching in a p‐i‐n doped multiple quantum well directional coupler

The quantum‐confined Stark effect observed in multiple quantum well (MQW) materials has been employed recently in a variety of electro‐optic devices. This communication reports on some encouraging results achieved with a MQW‐based, nonlinear vertical directional coupler. The device may be operated as an electrooptic switch through changes in the coupling length in response to large Stark shifts.

Second harmonic generation in InGaAsP waveguides at 1.3 μm wavelength

We report the first surface emission of red light from an InGaAs waveguide, generated by the nonlinear mixing of two counterpropagating guided waves at wavelengths around 1.3 μm. A nine layer InGaAsP/InP heterostructure was grown by low pressure MOCVD on 〈100〉 InP substrate. All layers were n‐doped with silicon to a level of 1.0×1017 cm−3. The structures functioned in both planar as well as ridge waveguide configurations. Measurements were performed with both a YAG laser and a semiconductor laser in the pulsed as well as the cw regime and were compared with theoretical calculations, used in the design of the structure. Red light was detected even in a single slab InGaAsP waveguide with a cw semiconductor laser diode.

Two-wavelength optical switching in a GaAs multiple quantum well directional coupler

Preliminary experimental results are reported on two‐wavelength switching in a GaAs‐based multiple quantum well planar directional coupler. It is verified that a novel design of the multiple quantum well (MQW) coupling region leads to a wavelength multiplexing/demultiplexing/switching operation. It is shown that control of such a function can be exercised by either the wavelength of operation or by an applied electrical voltage through exciton resonance effects in the MQW layer. The layer structure exhibits two exciton‐resonance peaks at which wavelength‐selective switching can be achieved.

Excitonic Versus Thermal Contribution To All-Optical Switching In A Nonlinear Multiple Quantum Well Directional Coupler Fabricated In GaAs.

In previous works we have demonstrated that the MQW-coupled directional coupler is a promising design for all-optical switching elements. Experimental analysis has revealed that an efficient intensity-dependent coupling can be achieved between the two waveguides for a sample length as short as 127 μm. However, due to the presence of two competing nonlinearities, namely excitonic and thermal, there is some concern over the nature of the switching. W e report here on results which support our claim that the dominant mechanism in this case, where we are operating at low powers near the heavy-hole resonance peak, is the faster excitonic nonlinearity.

Multiple Quantum Well Nonlinear Optical Directional Coupler As A Logic/Computing EI FMENT.

Applications of a multiple quantum well (MQW) nonlinear directional coupler to optical logic/computing are discussed. Very encouraging performance parameters are presented based on theoretical and experimental analysis of the element.