摘要:

A new method based on low-energy implantation is presented for the fabrication of laser diodes with shifted emission wavelength. The laser diodes are based on InGaAsP/InGaAs/InP material, with compressively strained active layers. Low-energy implantation(18keV As+)is used to generate vacancies near the surface of an incomplete laser structure, for which the epitaxial growth was interrupted45nm above the active layers of the device. The vacancies are subsequently diffused through the quantum wells by rapid thermal annealing. This diffusion causes a local intermixing of atoms at the interfaces of the active layers, which induces an increase of the band gap energy. The implantation/anneal process can be repeated several times to increase the amount of intermixing, thereby further shifting the emission wavelength. Once this process is completed, the upper optical confinement layer of the structure is overgrown using chemical beam epitaxy. Operational lasers with blueshifts as large as35nm were obtained. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120407

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We present a two-color (956 and 985 nm) InGaAs/AlGaAs laser structure epitaxially stacked through a low-resistance(10−5–10−4 &OHgr; cm2)Esaki junction, exhibiting two threshold characteristics. It is shown that this structure can be considered as a bipolar cascade laser. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120408

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Correlated measurements of emission spectra, photoluminescence and scintillation decays, thermoluminescence, and light yield were performed on a selected set of undoped and La-doped PbWO4single crystals. The samples were grown from5Npurity raw powders and show the blue emission component only. Distinct influence of La doping was found in the decays, thermoluminescence and light yield characteristics. It is discussed in the light of the direct influence of La doping on suppressing the creation of point defect centers in the PbWO4lattice, which are involved in the energy transfer and storage processes in this material. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120409

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A large increase in the quantum efficiency (QE) and open-circuit voltageVocof GaInAsSb thermophotovoltaic (TPV) devices is obtained by the use of an AlGaAsSb window layer compared with devices without a window layer. The TPV structure, grown on GaSb substrates by organometallic vapor phase epitaxy or molecular beam epitaxy, consists of a 1-&mgr;m-thickn-GaInAsSb base layer, a 3-&mgr;m-thickp-GaInAsSb emitter layer, a 100-nm-thick AlGaAsSb window layer, and a 25-nm-thick GaSb contacting layer. The band-gap energy of the lattice-matched GaInAsSb is 0.53–0.55 eV. The peak internal QE of the TPV cells with the window is>90&percent;,compared with less than 60&percent; for those without the window. At a short-circuit current density of∼1000 mA/cm2,Vocof∼300 meVis obtained for cells with the window layer, compared with less than 220 meV without the window layer. These increases are attributed to a substantial decrease in the surface recombination velocity with the window layer. Based on a standard calculation, the electron diffusion length in thep-GaInAsSb layer is at least 5 &mgr;m. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120497

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The influence of carrier relaxation on the emission dynamics of a semiconductor microcavity laser is investigated using femtosecond optical excitation. For moderate excitation intensities, the dynamics of the output laser pulse becomes significantly slower when the photon energy of the pump laser is tuned from the quantum well band-gap energy towards higher energies. Theoretical calculations reproduce this trend only if the interaction-induced dephasing of the polarization driven by the pump pulse, the formation, and relaxation of the nonequilibrium carrier distribution as well as the chirp of the excitation pulse are taken into account. Additionally, band-structure effects such as excitation of light holes influence the thermalization dynamics and lead to discontinuities in the general trend. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120498

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We report the operation of a III-V interband laser at a wavelength beyond 5 &mgr;m and temperatures above 90 K. The active region consists of a strain compensated broken gap four layer superlattice ofInAs/Ga0.6In0.4Sb/InAs/Al0.3Ga0.42In0.28As0.5Sb0.5grown by molecular beam epitaxy. The maximum operating temperature under 2.01 &mgr;m pulsed optical excitation was 185 K at a wavelength of 5.2 &mgr;m. The peak pump intensity at the 80 K threshold was62 kW/cm2,and the characteristic temperature(T0)of the threshold intensity was 37 K. ThisT0is comparable to the best observed values for 3–4.5 &mgr;m lasers based on the InAs/GaInSb material system. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120499

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

In this work, the efficiency of laser generation of surface acoustic waves (SAWs) in ceramic materials is reported to be wavelength dependent. A pulsed Nd:YAG laser operating at wavelengths of 1064 or 532 nm was used to generate SAWs on ceramic (silicon nitride and silicon carbide) and metal substrates. It was observed that 1064 nm radiation is more efficient than 532 nm radiation for SAW generation on ceramics, whereas the opposite is the case for metals. While the wavelength dependence of SAW generation efficiency in metals is due to stronger optical absorption at the shorter wavelength, the dependence for the ceramics is attributed to a longer absorption length at the longer wavelength. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120500

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We have fabricated ZnSe/ZnS quantum wires emitting at the shortest wavelength ever reported for a one-dimensional system. We show that inhomogeneous strain relaxation and Stark effect due to the internal piezoelectric field influence the ground level energy of the wires and overcome the quantum size effect. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120501

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

This letter describes the use of a sensitive photoresist for direct imaging of optical intensity profiles in near-field photolithographic experiments. A comparison between experimental patterns in exposed, developed photoresist and calculated profiles of intensity shows that this procedure provides a reliable semiquantitative image of the irradiance distribution in the near field; experiment and theory correlate adequately. A potential use of the superficial diffraction contrast recorded in photoresist as the basis for a new method of the fabrication of nanostructures is discussed. ©1997 American Institute of Physics. 

ISSN:0003-6951    

DOI:10.1063/1.120502

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The lasing of a Van de Graaff electrostatic accelerator–free-electron laser (EA–FEL) with an internal cavity is reported. An EA–FEL employing an internal cavity is a FEL configuration that has a potential to operate at high average power, high frequency, and possibly in a continuous wave (cw) mode. The initial lasing provided a pulsed radiation power of 1 kW at 100.5 GHz frequency. The FEL operated with a 1.4 A, 1.4 MeV electron beam in a recirculation (depressed collector) configuration. It utilizes a high quality(Q≈30 000)Talbot effect resonator and a Halbach-type wiggler placed internally in the center of the accelerator tank. Nonlinear features of the oscillation power buildup and decay near saturation and mode hopping were observed and are interpreted. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120503

出版商:AIP    

年代:1997

数据来源: AIP