摘要:

We report the first demonstration of a type II phase‐matched optical parametric oscillator using &bgr;‐barium borate (BBO) as the nonlinear optical material. The optical parametric oscillator (OPO) is pumped at 354.7 nm and tuning has been demonstrated over 0.48–0.63 &mgr;m and 0.81–1.36 &mgr;m. The linewidth of the device, without line narrowing elements, is 0.5–3.0 A˚, which is dramatically narrower than that of a corresponding type I phase‐matched BBO OPO. Experimentally usable conversion efficiencies of 12% have been achieved.

ISSN:0003-6951    

DOI:10.1063/1.103080

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

We report giant, nonlinear optical rectification in asymmetric quantum wells weakly coupled by an intermediate potential barrier. This phenomenon originates from (i) macroscopic displacements (30 nm) of carriers during optical transitions and (ii) large storage times of excited electrons because of a slow transfer mechanism between the wells (≊6 ps at 77 K). The resulting rectification coefficient is 1.62×10−3m/V per well, more than six orders of magnitude higher than in bulk GaAs. These structures really behave as giant ‘‘quasimolecules’’ optimized for infrared optical nonlinearities and their use may be envisioned for a new class of infrared detectors.

ISSN:0003-6951    

DOI:10.1063/1.103081

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Reduction of threshold current in GaAs/AlGaAs patterned quantum well (PQW) lasers grown by molecular beam epitaxy is studied. Application of high reflection coating results in threshold currents as low as 0.35 mA. Dependence of the measured threshold currents on the optical cavity losses agrees well with a simple model accounting for gain saturation in the quantum well active region. It is shown that gain saturation and finite optical confinement in the lateral direction lead to a minimum in the threshold current for an optimal width of the optical waveguide. Threshold currents as low as ∼100 &mgr;A are predicted for PQW lasers with ∼0.2‐&mgr;m‐wide active regions.

ISSN:0003-6951    

DOI:10.1063/1.103196

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Radiation from Ar+and Nd:YAG lasers is used within a metalorganic chemical vapor deposition reactor to thermally desorb selected areas of GaAs quantum well (QW) layers during a pause in the epitaxial growth. The process, called laser‐patterned desorption, is used to laterally pattern current confinement in an AlGaAs/GaAs diode laser structure. Current channels are produced by completely removing selected areas (∼3 mm wide) of ann+GaAs QW blocking layer embedded in the AlGaAspcladding of a separate confinement heterostructure laser. Scanning electron microscopy cross sections indicate the blocking layer is completely removed in regions illuminated with the focused laser beam. Current confinement is confirmed by observing the localized optical emission from a 1‐cm‐long bar containing a 1‐mm‐wide desorbed region. Broad‐area diode lasers fabricated from the sample exhibit a forward voltage varying from a minimum (∼2 V) within the lase‐desorbed region to a maximum (∼4 V) in the surrounding field. This work is the first demonstration of current confinement produced by epitaxial patterning in an optical device during growth.

ISSN:0003-6951    

DOI:10.1063/1.103082

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

In order to estimate deleterious effects caused by heating in continuous‐wave end‐pumped solid‐state lasers, the heat equation has been solved for an axially heated cylinder with a thermally conductive boundary at the periphery. Steady‐state thermal profiles are developed using both a full numerical solution and an analytic approximation which assumes only radial heat flow. The analytic solution, which is in good agreement with the numerical solution, is utilized to obtain an expression for the thermal focusing due to temperature‐induced refractive index changes. For Nd:YAG, 1 W of pump power deposited as heat is predicted to cause a thermal focusing length comparable to the cavity length of a typical diode end‐pumped laser.

ISSN:0003-6951    

DOI:10.1063/1.103083

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The transient behavior of the nonresonant nonlinear index is investigated in AlGaAs waveguides with femtosecond time resolution. Both the refractive index and the absorption changes are measured by time division interferometry and pump probe techniques. Different mechanisms which contribute to the nonlinear index are distinguished by examining their dynamics, including the optical Stark effect, resonantly excited carriers, and two‐photon absorption processes. The relative contribution from each mechanism is a strong function of wavelength near the band edge.

ISSN:0003-6951    

DOI:10.1063/1.103061

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

A new AlGaAs phased array laser structure with dummy stripes outside the stripe region is developed. The dummy stripes are dashed line stripes along both edge elements of the array stripes. Therefore, current in these dummy stripes does not cause lasing, but does increase the temperature of the edge elements. Thermal distribution in the array stripes, which mainly causes multimode oscillation in phased array lasers, is effectively unified by the dummy stripes. As a result, completely single lateral 180° mode continuous‐wave operation is realized for the first time in this novel phased array laser.

ISSN:0003-6951    

DOI:10.1063/1.103062

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

We report a GaAs mushroom structure surface‐emitting laser at 900 nm with submilliampere (0.2–0.5 mA) threshold under room‐temperature cw operation for the first time. The very low threshold current was achieved on devices which consisted of a 2–4 &mgr;m diameter active region formed by chemical selective etching, and sandwiched between two Al0.05Ga0.95As/ Al0.53Ga0.47As distributed Bragg reflectors of very high reflectivity (98–99%) grown by metalorganic chemical vapor deposition.

ISSN:0003-6951    

DOI:10.1063/1.103063

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The scanning photoelectron microscope at the National Synchrotron Light Source (NSLS) has recently recorded micrographs with a resolution below half a micron. To demonstrate elemental and chemical sensitivity at the submicron level, an artificial structure consisting of Al and SiO2lines on a boron‐doped silicon substrate was examined. Al 2pand Si 2pprimary photoelectrons as well as OKVVAuger electrons were used for image formation. Contrast reversal between the the Si and SiO2areas was observed in images formed from Si 2pand oxide‐shifted Si 2pphotoelectrons. The soft x‐ray undulator at the NSLS provides coherent illumination of a zone plate to produce the microprobe. The sample is mechanically scanned through the beam allowing the formation of images from photoelectrons detected by a single‐pass cylindrical mirror analyzer, or a more complete spectroscopic examination of a selected area of the sample.

ISSN:0003-6951    

DOI:10.1063/1.103064

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Heteroepitaxial InxGa1−xAs/GaAs structures have been formed for the first time by pulsed laser induced mixing of molecular beam epitaxy deposited In films (∼200 A˚) on GaAs (100) substrates. The process occurs by a melt‐induced, rapid‐mixing and solidification process driven by a XeCl pulsed excimer laser. The laser has a 27 ns full width at half maximum pulse width at 308 nm with its energy density of 0.28–0.61 J cm−2homogenized into a 4×4 mm square area which is stepped across the wafer. InxGa1−xAs layers withxvalues, as determined by both x‐ray diffraction and Rutherford backscattering spectrometry simulation ranging fromx=0.21–0.26 and thicknesses of 77–94 nm, have been formed. The formation of single‐crystal layers has been verified by4He ion channeling and cross‐section transmission electron microscopy.

ISSN:0003-6951    

DOI:10.1063/1.103065

出版商:AIP    

年代:1990

数据来源: AIP