摘要:

Rates of photodarkening and photodoping of silver were examined in binary PxSe1−xamorphous films over a wide range fromx=1 to 0.4. No monotonic change withxwas observed for either of the rates. The photodarkening rate remained almost constant in the ranges ofx<0.85, was reduced drastically by two orders of magnitude aroundx≊0.9, and became constant again in 0.95<x. A similar composition dependence was observed also for the photodoping rate. These results suggest that the presence of the critical composition in both rates is due to the change in the nature of uppermost orbitals of the valence band.

ISSN:0003-6951    

DOI:10.1063/1.104091

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

We report, for the first time, the growth of high quality InP/InGaAs multiquantum well modulator arrays onboththe [100] and the [1¯00] faces of the same InP wafer using an indium‐free wafer mounting technique in gas source molecular beam epitaxy.

ISSN:0003-6951    

DOI:10.1063/1.103359

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

An interferometric version of mirage technique is reported, whereby one part of the probe beam passes through the center of the thermal lens in air, while the other one avoids it. By mixing the two parts with the help of a diffraction grating, a strong photothermal signal is obtained at predetermined spots of the interference pattern. This photothermal arrangement is integrated into a reflected light microscope.

ISSN:0003-6951    

DOI:10.1063/1.103360

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The threshold conditions, under which a spatial subharmonic beam may arise when a Bi12SiO20crystal is illuminated by two pump beams, are investigated. It is shown that a nonlinear theory based on the material equations leads to good qualitative agreement with experiments

ISSN:0003-6951    

DOI:10.1063/1.104132

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

We report for the first time room‐temperature, continuous‐wave operation of individual vertical‐cavity laser diodes with submilliampere threshold currents. A single quantum well active region emitting at 979 nm surrounded by GaAs/AlAs Bragg reflector mirrors was used. Threshold currents were as low as 0.7 mA. A record low linewidth‐power product of 5 MHz mW and a linewidth as narrow as 85 MHz was measured. High yield and good uniformity were demonstrated.

ISSN:0003-6951    

DOI:10.1063/1.103361

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

To explore the ultimate threshold current limit in long‐wavelength semiconductor lasers, InxGa1−xAs/InP strained‐layer single quantum well laser diodes were studied for the first time by optically pumping with a 0.8 &mgr;m laser diode. Low‐threshold (≤92 A/cm2) cw operation was obtained and the lasing wavelength (1.62 &mgr;m) corresponding to the transition from the first quantization state of a 25 A˚ In0.8Ga0.2As well was observed. By taking the carrier collection efficiency (≤77%) into account, the actual threshold current density could be as low as 70 A/cm2.

ISSN:0003-6951    

DOI:10.1063/1.103362

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

We evaluate the effect of high‐reflectivity facet coatings on the threshold current of lattice matched and compressively strained InGaAs/InP quantum well lasers. A large decrease in the threshold current is observed in structures with low internal losses. Coated lasers exhibit threshold currents as low as 1.1 mA at 20 °C and 0.9 mA at 10 °C, down from ∼15 mA in as‐cleaved devices with cavity length of 200 &mgr;m. These changes are carefully modeled and the prospects for further reduction of the threshold current discussed.

ISSN:0003-6951    

DOI:10.1063/1.104085

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

GaAs/AlGaAs vertical‐cavity surface‐emitting lasers (VCSELs) with two semiconductor distributed Bragg reflectors (DBRs) were grown by molecular beam epitaxy. The threshold current was found to be 20–50% less on an average for VCSELs grown on the 4° off‐orientation (001) substrates than those on the on‐orientation ones. The lower threshold current was attributed to the smoother interfaces of the Al0.1Ga0.9As/AlAs DBRs in the off‐orientation growth observed by transmission electron microscopy. A threshold current and current density of 12 mA and 10.5 kA/cm2were measured with an emission efficiency of 0.2 mW/mA.

ISSN:0003-6951    

DOI:10.1063/1.104086

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Deposition of hydrogenated amorphous silicon films from SiH4/He gas mixtures was performed by using a square wave amplitude modulated rf discharge. The modulation was used for controlling radical densities in plasmas which led to a high rate deposition of good quality films. The fairly high deposition rate of 6 A˚/s was obtained for a low concentration of 5% SiH4and a high rf peak power 200 W (0.8 W/cm3) without any appreciable amount of powder particles in the reaction chamber. The optical gap of the films was 1.8–1.95 eV. Emission intensities of HeI 388.9 nm and SiH 413.5 nm linearly increased with rf peak power and were well correlated with the deposition rate.

ISSN:0003-6951    

DOI:10.1063/1.104087

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The electron energy distribution in low‐pressure pulsed power plasma switches is typically not in equilibrium with the local electric field. To simulate electron transport under these conditions a computer model has been developed and has been applied to the optically triggered pseudospark, or back‐lit‐thyratron (BLT). The model uses many groups of electrons divided into the ‘‘bulk’’ and the ‘‘beam’’. The bulk is represented by a fluid while the beam electrons are ballistic in nature and have not undergone significant energy‐loss collisions after generation. To account for beam electrons being generated at arbitrary locations in the BLT, multiple beams are employed in the model. The commutation phase of switching in the BLT is investigated and the onset of a hollow cathode effect during switching is predicted.

ISSN:0003-6951    

DOI:10.1063/1.104066

出版商:AIP    

年代:1990

数据来源: AIP