摘要:

Photoluminescence (PL) dynamics of localized excitons in a strongly coupled 40 A˚/40 A˚ GaAs/Al0.2Ga0.8/As superlattice under an electric field along the growth direction is reported. At zero field, a delayed PL formation due to the relaxation of dark excitons into radiative states is observed. With increasing field, both the PL decay time and the PL amplitude are strongly reduced. A rate equation analysis of the measured PL transients gives evidence that the field‐induced dissociation of nonradiative excitons is important. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113592

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Polarization of 8×8 vertical cavity surface emitting laser (VCSEL) arrays is completely controlled. These index‐guided VCSELs have a 6×5 &mgr;m rectangular poststructure consisting of DBR mirrors. All 64 VCSELs emit fundamental single‐mode and linearly polarized light with a polarization angle deviation of only 2.9°. Their light output characteristics are almost the same as those of conventional 6×6 &mgr;m polarization‐uncontrolled VCSELs. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113593

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Simulations have been performed for signal reproduction from a read‐only super resolution optical disk using a beam splitting method, in which a collimated laser beam generated by a laser diode is split into two beams with orthogonal polarizations and then recombined using polarizing beamsplitters. The beam with a higher power is used to raise the temperature of the mask layer, while the one with a lower power is employed to reproduce the recorded data. Tilting one of the laser beams against the other results in two laser spots partially overlapped at the focal plane, and the distance between the center of the two spots can be controlled by a galvanomirror. This allows signal readout with maximum resolution independent of the disk rotation speed. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113594

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We demonstrate the high‐contrast polarization‐rotation switching in semi‐insulating CdTe:Ga using a 30‐ps pump and probe pulses at a wavelength of 1.064 &mgr;m. It is found that the maximum switching contrast in the photorefractive cross‐polarization beam coupling configuration is about eight times higher for CdTe:Ga compared to undoped GaAs at fluences above 10 mJ/cm2. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113595

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

High‐efficiency diffractive elements with a graded volume distribution of refractive index are proposed, designed, and fabricated using thermal ion exchange in glass. A deliberate use of isotropic diffusion of ions enables us to generate, even with a single binary mask, a structure that acts like a continuous surface‐relief profile. The advantages of the proposed method include the ease of cleaning and antireflection coating the flat surface, the absence of alignment problems in the fabrication process, and compatibility with stacked planar optics. A grating beam splitter with three equal‐efficiency central orders and 89.7% diffraction efficiency is demonstrated. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113596

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A periodic dependence of kink power on laser length is observed and explained. Weakly index guided high power stripe lasers in the AlGaAs, InGaAlP, and InGaAs–AlGaAs material systems are studied and oscillation periods of 100–350 &mgr;m are found. Relative kink power differences exceeding a factor of 4 are observed. Facet coatings lead to differences in the oscillation amplitude but not in the oscillation period. The observations indicate that phase‐locked fundamental and first‐order modes exist at certain preferred laser lengths. This general model fully explains the oscillatory behavior of the kink power and the correlated changes in lateral far field distributions at the front and rear mirrors. It is concluded that the optimum diffraction limited power output can be obtained by choosing the proper laser length. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113597

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Nonresonant third‐order harmonic generation from CdS clusters encapsulated in zeolite A and X was observed at a fundamental wavelength of 1900 nm. To avoid scattering from the surfaces of the small zeolite crystals, the powder samples were dispersed in a liquid with nearly the same refractive index as that of the samples. The third‐order optical susceptibilities of CdS‐encapsulated zeolite A and X estimated from the intensity of their Maker fringe patterns were 4.1×10−12and 1.1×10−11esu, respectively. These values were slightly smaller than those reported for the 1.5 nm surface‐capped CdS cluster. The hyperpolarizabilities of CdS clusters encapsulated in zeolite A and X were estimated by assuming the Lorentz local field to be in the range of 380–480×10−36and 270–390×10−36esu, respectively. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113598

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Lasing of Nd3+ions in different crystallographic sites of KYF4has been demonstrated to occur at different wavelengths. Low threshold, high efficiency lasing performance at 1041 and 1302 nm were achieved under selective pumping conditions. The stimulated emission cross section at 1041.2 nm was estimated to be 2.6×10−19cm2and the radiative lifetime was found to be 600 &mgr;s. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113599

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Dispersions of nematic liquid crystal microdroplets in silica glasses have been obtained by sol‐gel processes, forming gel‐glass dispersed liquid crystals (GDLCs). GDLC microdroplet size may be adjusted precisely by controlling the sol‐gel reaction. This allows the preparation of scattering media with different spectral response, which can be further modified by reorienting the liquid crystal microdroplets with external electric fields. Opaque/transparent and dichroic GDLC thin films have been prepared. An extension of the general scattering theory is used for explaining their optical behavior. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113600

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The third‐order nonlinear optical properties of multilayered films containing 23% by weight of an axially modified silicon phthalocyanine derivative have been measured by degenerate four‐wave mixing at 532 nm with 70 ps full width at half maximum pulses. The average &khgr;(3)of the films measured at (1.33±0.15) ×10−11esu using CS2as a standard and the cubic hyperpolarizability ⟨&ggr;⟩ was calculated at (1.97±0.22)×10−32esu. The degenerate four‐wave mixing signal profile indicates that the films have a response time better than 70 ps. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113601

出版商:AIP    

年代:1995

数据来源: AIP