摘要:

High‐quality epitaxial PbxSn1−xTe films have been obtained for the first time on Ge substrates. The films have been deposited employing a rf multicathode sputtering system capable of simultaneous and sequential sputtering at different rates from three different targets. Heteroepitaxial films of PbxSn1−xTe at substrate temperatures lower than the ones needed in conventional evaporation techniques have been obtained using NaCl and BaF2substrates. Using the cosputtering technique, it has been possible to obtainn‐type andp‐type PbxSn1−xTe layers by controlling the quantity of excess metal, or tellurium, respectively. Electrical properties close to the best reported single‐crystal values have been measured. Middle‐infrared detector arrays have been made using PbxSn1−xTe films deposited on silicon and germanium substrates since such substrates can easily incorporate the electronic readout elements for a completely integrated thermal imaging system. Peak detectivity values up to 2.4×108cm Hz1/2/W have been measured in photoconductive epitaxial thin films. Polycrystalline films deposited on SiO2‐covered Ge and Si substrates have shown exceptionally high responsivity values (480 V/W). Peak detectivities,D*&lgr;(8.5 &mgr;, 800,1), higher than 109cm Hz1/2/W have been obtained with a 2&pgr;‐sr field of view at an operating temperatue of 77°K. Measurements of noise, responsivity, and detectivity of linear detector arrays are reported.

ISSN:0021-8979    

DOI:10.1063/1.1663803

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Thermodynamic calculations are presented which provide explicit expressions for the combined temperature and phosphorus partial pressure dependences of the Ga‐ and P‐vacancy concentrations in GaP. This work extends the applicability of earlier results for the vacancy concentrations, obtained by an analysis of the solidus data, from solid‐liquid (i.e., LPE and LEC growth) to solid‐vapor equilibria (vapor growth, annealing, and diffusion). The calculations are represented in the form of Ga‐ and P‐vacancy concentration and solid‐composition isobars. In addition, the previously established correlation between the reciprocal of the nonradiative shunt‐path lifetime (1/&tgr;n) and the relative Ga‐vacancy concentration for GaP crystals prepared by a variety of techniques is transformed into a correlation with absolute vacancy concentrations. The electron‐capture cross section of a Ga‐vacancy behaving as a shunt path inp‐type material is estimated to be ∼4.5×10−17cm2. Finally, the Ga‐vacancy concentration isobars and the 1/&tgr;ncorrelation are discussed in the context of LPE, vapor growth, and annealing processes for GaP.

ISSN:0021-8979    

DOI:10.1063/1.1663804

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The pressure dependence of the energy gap has been determined at 63 and 77°K for GaSb, InAs, and InSb by tuning their laser‐emission frequencies with hydrostatic pressures up to 8 kbar. The pressure variation of mode frequency and refractive index has also been measured for each semiconductor. The laser threshold and emission intensity are essentially independent of pressure in GaSb and InAs. For InSb, however, the application of pressure dramatically decreases the threshold and increases both spontaneous and stimulated emission. A number of experiments have been performed to determine the cause of these pressure effects. The data are consistent with a mechanism involving nonradiative recombination between nearly overlapping bandtails within the energy gap which separate with pressure.

ISSN:0021-8979    

DOI:10.1063/1.1663805

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Total light output of GaAs laser diodes has been measured at 300 and 76°K before and after successive neutron irradiations to a cumulative fluence of 6.5×1014neutron/cm2(> 10 keV). The range of current densities used extended from well below the laser threshold current density to the maximum allowable value. Both the subthreshold light output and the threshold current density were sensitive to neutron damage in agreement with previous observations. However, at current densities significantly above threshold the light output is much less sensitive to irradiation and, in fact, the light output at 76°K was observed to increase following irradiation. These latter results have significant practical importance for cases in which laser diodes must operate in a radiation environment.

ISSN:0021-8979    

DOI:10.1063/1.1663806

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Single‐crystal sapphire was found to lose some of its original transparency in the near infrared (0.9 &mgr;m) when subjected to strong dynamic compression in the pressure range between 100–130 GPa (1–1.3 Mbar). Experimental evidence of this phenomenon is presented and discussed in relation to some of the other known properties of the crystal.

ISSN:0021-8979    

DOI:10.1063/1.1663807

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Mode conversion in a periodically perturbed thin‐film optical waveguide is studied in detail. Three different types of perturbations are considered: periodic index of refraction of the film, periodic index of refraction of the substrate, and periodic boundary. The applications in filters, mode converters, and distributed feedback lasers are discussed.

ISSN:0021-8979    

DOI:10.1063/1.1663808

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The spontaneous emission from HF infrared bands in the free jet of a continuous HF chemical laser with a slit nozzle bank has been measured at a number of downstream positions. Three flows are reported: He&sngbnd;SF6&sngbnd;H2‐(1) with O2, (2) without O2, and (3) with reduced SF6without O2. Spatially averaged number densities of the HF vibrational levels (&ngr; = 1, 2, 3, 4) have been determined during zero‐power conditions. Vibrational nonequilibrium is evident. The largest HF densities are ∼1015No./cm3. Observed rotational temperatures, equilibrated to jet static temperature, range from 560 down to 390°K. The largest zero‐power gain coefficient deduced is 0.12 cm−1on thePbranch of the 2 → 1 band.

ISSN:0021-8979    

DOI:10.1063/1.1663809

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The ignition of laser‐supported detonation waves is caused by the thermomechanical response of the target. The blown‐off material acts as an accelerating piston creating a shock wave in air. The small amount of free electrons created by the shock wave is cascaded to plasma densities by light absorption. The theory explains a number of conclusions which have been experimentally verified. Numerical results agree with observed data.

ISSN:0021-8979    

DOI:10.1063/1.1663810

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

This paper discusses two characteristics necessary for efficient laser‐induced transfer of organic colorants. Results analyzed on a scanning electron microscope and scanning microdensitometer suggest that the material transfer is caused by melting and vaporization.

ISSN:0021-8979    

DOI:10.1063/1.1663811

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Holograms of diffuse opaque objects which are submerged in water are difficult to obtain using a cw laser if the object is to be viewed from the top of the container. Experiments and theory are described which indicate that the major cause of the problem is excitation of unstable surface waves. When the object and container are on a stabilized table suitable for normal holography, these waves are excited by small residual oscillations of the table. Surface wave amplitudes can be of sufficient height and frequency to ruin the hologram. A simple solution to this problem is presented.

ISSN:0021-8979    

DOI:10.1063/1.1663812

出版商:AIP    

年代:1974

数据来源: AIP