D.A.H. Mace

Sub-band energies of highly strained InGaAs-GaAs quantum wells

The sub-band energies of InxGa1-xAs quantum wells strained between GaAs barriers and substrate are calculated using a model which takes into account strain, nonparabolicity and quantum well effects. A comparison is made with low-temperature photoluminescence and photoluminescence excitation spectra of InxGa1-xAs quantum wells for which x=0.28. The transitions 1H-1C, 1L-1C and 2H-2C have been identified for the 7.5 nm well.

A novel twin-ridge-waveguide optical amplifier switch

A novel twin ridge-waveguide optical amplifier switch is reported. The technique of hydrogen passivation of acceptors has been applied to decrease the current spreading in the region between the ridges. The incorporation of a passive waveguide below the active waveguide leads to the result that using 1.53 mu m TE polarized light, through and cross states, each with only 1 dB insertion loss, fiber-to-fiber, can be selected in a device of 360 mu m length by varying the currents to each ridge with a total current of 140 mA. A minimum crosstalk of less than -33 dB was achieved when the cross state was selected. This is the first report of a twin ridge-waveguide amplifier switch with such a low-loss, low-polarization sensitivity, and low crosstalk.<<ETX>>

Nonlinear-optical absorption in InGaAs/InAlAs multiple quantum wells.

We have measured the room-temperature intensity dependence of the optical transmission of an In(0.53)Ga(0.47)As/In(0.52)Al(0.48)As multiple-quantum-well structure from 1.5 to 1.7 microm. The absorption is calculated from the transmission by taking into account the wavelength dependence of the reflection coefficients. An intensityof 15 kW cm(-2) is required to reduce the absorption by one half for excitation at the edge of the 1H-lC transition absorption band. For intensities exceeding 10(7) W cm(-2), complete saturation of the absorption is observed. A theoretical model is described that fits the intensity dependence of the absorption right upto saturation at two wavelengths and predicts a carrier lifetime of 0.75 nsec, which has been confirmed by independent measurements.

Carrier recombination time measurements of InAlAs/InGaAs multiple quantum wells using nonlinear frequency-dependent transmission

A novel method for measuring the carrier recombination time of a semiconductor which requires only a single semiconductor laser source is described.

Integrated lossless InGaAsP/InP 1-to-4 optical switch

The fabrication and performance of a 1-to-4 channel optical splitter/combiner are described. The design is based on the integration of a number of twin-guide amplifiers interconnected by active ridge waveguides. Lossless operation is seen fiber-to-fiber for all four ports for TE input light, with a 3-dB bandwidth of 20 nm. >

An optical tap based on the twin waveguide laser-amplifier with asymmetric flared output waveguides

An optical tap based on the twin waveguide laser-amplifier with asymmetric flared output waveguides is presented. The new optical tap exhibits gain, allows the tap channel gain to be electrically controlled over a dynamic range of 30 dB, without greatly affecting the through channel gain and is optically broadband. The general features of the optical tap can be understood from coupled mode theory.<<ETX>>

Nonlinear Optical Absorption In InGaAs/InP And InGaAs/InA1As Multiple Quantum Well Structures

We have measured the intensity dependence of the room temperature optical transmission of an In.53Ga.47As/InP multiple quantum well (MQW1) and an In .53Ga.47As/In.52A1.48As multiple quantum well (MQW2) from 1.5μm to 1.7μm. The absorption is calculated from the transmission taking into account the wavelength dependence of the reflection coefficients. At the edge of tlAe 1H-1C transition absorption band the absorption is found to fall by 1/2 if the intensity is 16kWcm-2 and 15kWcm-2 at the surface of MQW1 and MQW2 respectively and is completely saturated at intensities exceeding 107 Wcm-2 , showing no nonsaturable absorption. A theoretical model is described, which fits the intensity dependence of the absorption right up to saturation at two wavelengths with an assumed carrier lifetime of 0.66ns for MQW1 and 0.75ns for MQW2.