Jiying Zhang

Spontaneous and stimulated emission in ZnCdSe/ZnSe asymmetrical double quantum wells

The spontaneous and stimulated emission in ZnCdSe/ZnSe asymmetric double quantum wells have been studied. The exciton photoluminescence both in the narrow well and in the wide well is influenced by two factors, the exciton tunneling and the thermal dissociation processes. The change of the emission intensity is determined by the stronger one. The carrier tunneling through the thin barrier is conductive to the stimulated emission from the wide well, and the threshold can be lowered by optimizing the structure.

Formation and photoluminescence of self-assembled CdSe quantum dots

Self-assembled CdSe quantum dots (SAQDs) were fabricated by lower pressure metal organic chemical vapor deposition. 2MLs of CdSe coverage were deposited directly on GaAs(100) substrates. The formation process of CdSe SAQDs was monitored by atomic force microscopy. The formation of SAQDs below critical thickness was contributed to the effect of surface diffusion and releasing strain. The SAQDs PL spectrum was studied primitively.

Optical bistability in a ZnTe/CdZnTe multiple quantum well optical bistable device at room temperature

The band edge nonlinear absorption in ZnTe/CdZnTe multiple quantum wells (MQWs) is studied at room temperature. It is found that the exciton absorption peak tends to saturate, broaden and the absorption edge shift to lower energy side with increasing of pump intensities. The optical bistability in ZnTe/CdZnTe MQWs optical bistable device is investigated on transmission at room temperature. The research result indicates that the threshold and contrast ratio for the optical bistability in ZnTe/CdZnTe MQWs optical bistable device are about 292.5 kW/cm2 and 3:1, respectively.

Room-temperature excitonic optical properties in ZnSe-ZnS/GaAs multiple quantum wells

Excitonic optical bistability with nanosecond switching time in ZnSe-ZnS multiple quantum wells (MQWs) with a Fabry-Perot (FP) cavity is investigated at room temperature. The research result indicates that the threshold and contrast ratio for the optical bistability in ZnSe-ZnS MQWs with a FP cavity are about 0.2 MW/cm2 and 6:1, respectively. On the basis of the room temperature excitonic absorption spectra obtained here, we attribute the major nonlinear mechanism for the optical bistability to the excitonic saturating absorption due to phase space filling of excitonic states and excitonic band broadening.

Impurity process in ZnCdSe/ZnSe multiple quantum wells

At high excitation intensity the photoluminescence (PL) spectra of ZnCdSe/ZnSe multiple quantum wells were studied, which showed strong excitonic emission and a broad emission band at low energy side. The dependence of the broad emission band on excitation intensity shoed obviously that the broad emission band is related to impurity. In time resolved luminescence spectra, with increasing the delay times (ns), the broad emission band shifts to low energy side and full width at half maximum decreased, which showed the typical characteristic of donor-acceptor pairs (DAP) emission. And then, the reason that the excitonic emission peak and the DAP band decay with same speed was discussed and it was attributed to the free carriers relax effect.

Second-harmonic generation in ZnCdSe/ZnSe asymmetric double quantum wells

Abstract Second-harmonic generation in ZnCdSe ZnSe asymmetric double quantum wells (ADQW) was observed using the Maker fringe technique. It is due to the noncentrosymmetric characteristics of ADQW, which make X(2) not equal to zero. The birefringence in ADQW was also observed by finding the point of phase match between fundamental wave and second harmonic.

Saturating refractive nonlinearities and optical bistability in ZnSe/CdZnSe MQWs at room temperature

The excitonic nonlinear refractive index was calculated by using Kramers-Kronig relation and the saturating absorption of ZnSe/CdZnSe multiple quantum wells (MQWs) was studied under different pump intensities. The maximum nonlinear refractive index change is about -6.19 X 10-3. Excitonic optical bistability in ZnSe/CdZnSe MQWs is investigated at room temperature. The result indicates that the threshold and contrast ratio for the optical bistability in ZnSe/CdZnSe MQWs are about 210Kw/cm2 and 2:1, respectively. On the basis of the excitonic nonlinear theories and excitonic absorption spectra in the ZnSe/CdZnSe MQWs, we attribute the major nonlinear mechanism of the optical bistability in the ZnSe/CdZnSe MQWs to the phase space filling of excitonic states and excitonic band broadening due to exciton-exciton interactions.

Carrier tunneling in ZnCdSe/ZnSe asymmetric double-quantum-well structure

Optical characteristics of ZnCdSe/ZnSe asymmetric double- quantum-well structure grown by LP-MOCVD were studied. By analyzing the photoluminescence spectra, we found that the excitation power and temperature could influence the tunneling of the excitons, and due to different tunneling time of electrons and holes, space-charge effect was observed.

ZnTe/CdZnTe MQWs optical bistable device on transmission at room temperature

ZnTe/CdZnTe multiple quantum wells (MQWs) optical bistable device has been fabricated, and optical bistability in ZnTe/CdZnTe MQWs optical bistable device is investigated on transmission at room temperature. The research result indicates that the threshold and contrast ratio for the optical bistability in Zn-Te/CdZnTe MQWs optical bistable device are about 363 kW/cm2 and 4:1, respectively. On the basis of the excitonic nonlinear theories, excitonic absorption spectrum in the ZnTe/CdZnTe MQWs obtained here, we attribute the major nonlinear mechanism for the optical bistability to the saturating effect of excitonic absorption.

Optically pumped ZnSe-ZnS MQWs blue vertical cavity surface emitting lasers

We describe the fabrication and operation of vertical cavity surface emitting lasers (VCSELs) by pulsed optical pumping. The VCSELs structure is a ZnSe-ZnS MQWs with a Fabry-Perot cavity. The stimulated emission in ZnSe-ZnS MQWs VCSELs is observed at thresholds of 3.6MW/cm2 with the wavelength near 440nm at 77K. On the basis of the absorption and photoluminescence spectra in the ZnSe-ZnS MQWs, we attribute the major physics mechanism for the stimulated emission of ZnSe-ZnS MQWs VCSELs to exciton and exciton interactions.