摘要:

We have studied metalorganic molecular beam epitaxy growth on strain‐compensated multi‐quantum‐wells (MQWs) in which well layer tensile strain ranges from 0.5 to 1.45%. Double‐crystal x‐ray and cross‐sectional transmission electron microscopy study reveal that each layer in the six‐well, 1.3% strained MQWs has well‐defined flat interfaces. The photoluminescence intensities of the MQWs are comparable to those of lattice‐matched MQWs and remain unchanged after 620 °C annealing. The threshold current density (Jths) of six‐well MQW lasers emitting at 1.3 &mgr;m wavelength decreases when increasing the tensile strain from 0.5 to 1.3%. TheJth and the threshold current of the 1.3% strained MQW lasers with a 300 &mgr;m cavity length are 0.6 kA/cm2and 9 mA, respectively. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116440

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We have constructed a non‐biased all‐optical bistable device using electroabsorption in multiple quantum wells (MQWs). The device is made of a serial connection of two identical doublep‐i‐n(p‐i‐n‐i‐p) diode structures within asymmetric Fabry–Perot (AFP) cavity. This scheme ensures both large internal electric field swing and full exploitation of the light intensity. From the measurement of the diode properties, the non‐biased bistability parameters—reflection change of 19%, contrast ratio of 17:1, and bistable loop width of 70%—were obtained. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116441

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

The device performance of light‐emitting electrochemical cells is improved by adding a bifunctional liquid additive into the light‐emitting layer. Because of the surfactant‐like character of the additive, the light‐emitting layer exhibits a high surface area bicontinuous three‐dimensional network morphology. The semiconducting polymer forms a continuous network phase enabling electronic transport of injected electron and holes: the electrolyte forms a continuous network phase enabling fast ion transport; the nm length scale of the phase separated network enables rapid, effective transport of the ions into the conducting polymer during electrochemical doping. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116442

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We report on time‐resolved photoluminescence study of AlxGa1−xAs spontaneous vertical quantum well (SVQW) structures on GaAs V‐grooved substrates. Four distinct photoluminescence peaks are observed originating from the spatial nonuniformity of the alloy compositions spontaneously formed during metalorganic vapor phase epitaxial growth. The decay time of the (111)A sidewall AlGaAs decreased with increasing temperature, while that of the SVQW increased. The rise time of the SVQW was found to be longer than the typical value of the exciton formation and increases with increasing temperature, indicating that the exciton formation is not limiting factor of the rise time. These results are explained in terms of the exciton diffusion toward the SVQW from the outer AlGaAs layers with less Ga compositions. In addition, two dimensionality of the SVQW was evidenced by temperature dependence of the radiative lifetime. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116443

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We report the measurement of the dynamics of free‐space electro‐optic field sensors for pulsed electromagnetic wave radiation. With an optical probe power spanning six decades of linearity and excellent signal‐to‐noise ratio (SNR), it is feasible to convert a far‐infrared 2D image into an optical 2D image. A simple estimation indicates that 100 mW of optical probe power can achieve an image of 256×256 pixels with a 50 pA signal current per pixel and a SNR ≳200. We also present a comparison measurement of an ultrafast photoconductive antenna and an electro‐optic sensor crystal. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116444

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

A reflection‐grating measurement technique is reported for measurement of the electro‐optic coefficient in crystalline strontium barium niobate thin films grown using pulsed laser deposition. The measurement yields a value of about 350 pm/V for ther33coefficient of the Sr0.6Ba0.4Nb2O6(SBN:60) film. The measurement technique is based on a modulated diffraction pattern measurement using coplanar electrodes and can be extended to a range of cases where it is not possible to deposit electrodes on both sides of a film. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116445

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We show that energy positions of features in photoluminescence and photoluminescence excitation (PLE) spectra can be obtained more accurately by Fourier transforming segments of these spectra and analyzing the resulting coefficients in reciprocal space than by using conventional real‐space analysis. Fourier transform analysis is particularly advantageous where base line effects are significant, as in PLE. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116446

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We have tested a series of high‐Q photonic band gap (PBG) resonant cavities in the mm‐wave regime and achieved a cavity‐Q of 2.3×104, the highest value reported among all two‐ and three‐dimensional PBG cavities. We have also systematically varied the size and reflectivity of such cavities to study their effect on cavity properties such as cavity modal frequency, linewidth, and cavity Q value. We show that the resonant frequencies can be tuned throughout the PBG regime and that linewidths (or equivalently Q value) can be varied over two orders of magnitude (i.e., a Q value from ∼2.7×102to 2.3×104). ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116558

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

A femtosecond four‐wave mixing technique is used to measure the ultrafast coherent dynamics of the optical polarization in semiconductor optical amplifiers. A heterodyne detection scheme enables us to measure a background‐free quasi‐degenerate four‐wave mixing signal even without spatial separation of the pump and probe beam. First results indicate that the polarization dephasing time close to the transparency point is on the order of 100 fs. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116559

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We have used the discrete‐dipole approximation (DDA) method, implemented as a modified version of theDDSCATprogram of Draine and Flatau, to calculate 3D light scattering intensity diagrams for individual oxide particles present in Czochralski silicon wafers. The particles were either octahedra or plates with normalized sizesx=0.01–5. The signals that would be measured for light scattered through 90° or 180° were determined from the diagrams, these angles corresponding to the cases of light scattering tomography (LST) and reflection confocal (RC) scanning infrared microscopy (SIRM), respectively. The results show that asxincreases, the signal (particle image contrast) increases ∝x6forx<∼1, but increased more slowly and in an irregular manner forx≳∼1. The signal also depends markedly on the particle shape and orientation. These findings demonstrate the difficulty of deducing quantitative data, e.g., individual particle sizes, from SIRM image contrasts. However, they also indicate the type of measurements that need to be made and provide a basis for the quantitative interpretation of the experimental results. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116560

出版商:AIP    

年代:1996

数据来源: AIP