摘要:

Data are presented on laser threshold current density and emission wavelength of strained‐layer InGaAs‐GaAs‐AlxGa1−xAs single quantum well lasers having confining layer aluminum compositions in the range 0.20≤x≤0.85. A decrease in threshold current density with increasing confining layer composition is related to the increased confinement factor of the waveguide structure. An increase in the laser emission wavelength is observed as a consequence of reduced bandfilling.

ISSN:0003-6951    

DOI:10.1063/1.103408

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

We have for the first time demonstrated two‐beam coupling energy transfer at a wavelength of 1.5 &mgr;m. Beam coupling gain coefficients of 0.6 cm−1have been obtained in vanadium ‐doped CdTe with only 5 mW/cm2incident intensity. These gain coefficients exceed typical gain coefficients in GaAs at 1.06 &mgr;m wavelength by 50%. In preliminary measurements using the moving grating technique, we have measured a gain coefficient of 2.4 cm−1. Through adjustment of the doping level, CdTe:V can be used as a sensitive photorefractive material through the 0.9–1.5 &mgr;m spectral range.

ISSN:0003-6951    

DOI:10.1063/1.103409

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

For the first time, the enhanced low‐frequency relative intensity noise characteristics of semiconductor lasers is explained. It is shown, by multimode rate equation analysis, that the enhanced low‐frequency noise is caused by coupling between longitudinal modes which can renormalize the resonance frequency of the individual modes to very low values. It is further shown that a single‐mode laser will also exhibit enhanced low‐frequency noise unless the side‐mode suppression is high.

ISSN:0003-6951    

DOI:10.1063/1.103385

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The generation of a 16 &mgr;m laser beam through cascading in a downstream‐mixing CO2gasdynamic laser is studied. To simulate actual lasing action, a generalized, two‐dimensional, flow‐radiation‐coupled power extraction model for a gasdynamic laser is used. Also, to model the cascade process a new four‐mode CO2‐N2vibrational kinetic model has been proposed. The steady‐state intensity obtained for an exclusive 9.4 &mgr;m transition is of the order of 5×107W/m2. In the cascade mode of operation the steady‐state intensities for 9.4 and 16 &mgr;m transitions of the order of 5×107W/m2and 1.0×106W/m2, respectively, have been obtained.

ISSN:0003-6951    

DOI:10.1063/1.103386

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

We demonstrate a novel waveguide polarization controller that allows endless transformations from any varying general input polarization state into any varying general output state. The electro‐optic controller is implemented in lithium niobate and produces adjustable elliptical birefringence of constant total phase retardation via three independent drive voltages. We show that it allows fast and reset‐free automatic polarization control using an entirely analog feedback circuit that derives its error signal from the intensity in the prescribed output polarization.

ISSN:0003-6951    

DOI:10.1063/1.103387

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Self‐pumped and double phase conjugation are first demonstrated in undoped GaAs with applied dc electric field at 1.06 &mgr;m wavelength. Phase‐conjugate reflectivities of up to 3% and 0.5% respectively, are obtained and other dependences are reported. Reported values of the self‐pumped phase‐conjugate reflectivity are compared with those of InP.

ISSN:0003-6951    

DOI:10.1063/1.103388

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The production of H−ions at a barium converter immersed in a hydrogen plasma has been investigated experimentally for a pulsed discharge. It is found that the scaling of the negative ion output with incident positive ion current on the converter depends greatly on the actual geometry of the plasma generator. A less than linear scaling is observed in a multicusp system. A more than linear scaling is obtained in a configuration where the filament and the converter are separated by a permanent magnet filter.

ISSN:0003-6951    

DOI:10.1063/1.103389

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

An optical technique for obtaining two‐dimensional spectra of turbulent flows is presented. A coherent beam is passed through a turbulent flow and acquires phase perturbations which are related to the density field of the flow. This phase‐modulated beam is focused to obtain the Fourier transform of the incoherent, fluctuating portion of the field. The coherent portion of the field is removed by exploiting the photorefractive properties of BaTiO3as a temporal filter. The technique is an improvement over existing methods in that it is nonintrusive, has a wide dynamic range, and requires no assumption of isotropy of the turbulence.

ISSN:0003-6951    

DOI:10.1063/1.104263

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

This letter critically discusses the topographical information obtained by scanning tunneling microscopy (STM) on surfaces with a mesoscopic roughness, i.e., in the range of some nm’s. In a foregoing publication [J. Appl. Phys.67, 1156 (1990)], we already treated the evaluation of constant current images based on the knowledge of the real surface and the shape of the tunneling tip (‘‘tip shape limited resolution’’). Now we deal with the invers problem: the reconstruction of the real surface topography based on the corresponding STM image and the tip shape, using a simple, straightforward formalism.

ISSN:0003-6951    

DOI:10.1063/1.103390

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Employing the on‐site tight‐binding Koster–Slater Green’s function method, the deep energy levels of two series of paired substitutionalsp3‐bonded impurities in the II‐VI wurtzite semiconductor ZnS are presented. The chemical trends in the deep levels, as the spectator impurity varies, are predicted.

ISSN:0003-6951    

DOI:10.1063/1.103391

出版商:AIP    

年代:1990

数据来源: AIP