摘要:

The structure of GaAs/AlGaAs quantum wires (QWRs) and vertical quantum wells (VQWs) grown by low‐pressure organometallic chemical vapor deposition was investigated by conventional and high resolution transmission electron microscopy, and by low‐temperature cathodoluminescence. The lower wire boundaries show a much smaller radius of curvature, as compared with atmospheric pressure growth of similar structures, and the upper boundaries show distinct faceting. More abrupt interfaces are obtained due to the kinetically limited growth, with measured interface grading as small as one or two monolayers. The VQW structures formed in the AlGaAs barrier exhibit several branches related to the faceting of the QWR boundaries. These characteristics of the low‐pressure nonplanar growth should allow the fabrication of quasi‐one‐dimensional QWRs with size and shape controlled on the monolayer level. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114923

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The optimization of growth conditions for high quality 1.3 &mgr;m InAsP/InGaAsP laser structures by gas source molecular beam epitaxy is reported. Measurements of photoluminescence intensity and threshold currents of highly strained InAsP/InGaAsP multiple quantum well (MQW) lasers indicate an optimum growth temperature substantially lower than that for conventional 1.3 &mgr;m InGaAsP quaternary lasers. Broad‐area laser structures grown under the optimum conditions exhibited threshold current densities as low as 400 A/cm2. Buried heterostructures with uncoated facets exhibited threshold currents as low as 5.0 mA and internal losses of 8.0 cm−1. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114924

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A hybrid neodymium (Nd) laser that contains Nd:YLF and Nd:phosphate glass media in a single cavity was demonstrated. In a wide range of gain conditions, the original lasing spectrum of Nd:glass can be suppressed and the hybrid laser spectrum was ‘‘locked’’ to that of Nd:YLF, even when Nd:YLF was pumped below its threshold. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114925

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The influence of straight dislocations on the second order nonlinear optical susceptibility &khgr;(2)of cubic noncentrosymmetric media has been modeled. The resulting degradation of &khgr;(2)has been evaluated for screw and edge dislocations in GaAs. It is found that single screw and edge dislocations reduce the &khgr;(2)of GaAs by a third and ∼60%, respectively. This implies that second order nonlinear optical effects are very sensitive to misfit dislocation generation in epitaxially grown noncentrosymmetric media and that dislocation‐free epilayers are required to realize the optimum &khgr;(2). ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114926

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Grating coupled surface emitting lasers with rectangular as well as blazed grating outcouplers were investigated. Horizontal cavity InGaAs/AlGaAs laser oscillators, with two rectangular first order surface gratings as feedback elements, were integrated with single detuned rectangular or blazed second order gratings as surface output couplers, using electron beam lithography and chemically assisted ion beam etching. Superior differential quantum and surface emission efficiencies of 56% and 84%, respectively, were measured for lasers with optimized blazed output couplers. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114927

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Terahertz radiation emitted from (111) InSb illuminated with focused 1.4 &mgr;m laser pulses is due to both difference‐frequency mixing and depletion field driven current. By rotating an undoped (111) InSb sample at a temperature of 80 K about its surface normal, we were able to separate the relative contribution of the azimuthally dependent difference‐frequency mixing (DFM) signal from the total terahertz wave form. Contrary to expectations, it was found that the azimuthallydependentspectrum appears nearly identical to the azimuthallyindependentspectrum. From this, it is concluded that the spectrum of the current surge signal blue shifts as the pump is focused. Also, a strong similarity exists between the temperature dependence of the DFM and current surge signals. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114928

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A variable output coupling scheme is described for a stretched‐pulse polarization additive pulse mode‐locked (APM) fiber ring laser. The scheme allows the coupling percentage to be changed while the laser is running and allows for the maximum possible power extraction before cavity losses inhibit mode‐locked operation. We describe how the nonlinear pulse dynamics change to compensate the change in cavity loss. Compared to high power output coupling schemes that use the APM rejection port, this method provides cleaner output pulses at comparable output powers. Pulse energies of 0.39 nJ are obtained at 48% output coupling in a diode‐pumped system. 88 fs pulses with time‐bandwidth products of 0.49 are obtained after output chirp compensation using a silicon prism pair. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115351

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We report the effect of the rapid thermal annealing (RTA) of amorphous silicon oxynitride (a‐SiOxNy:H) thin films on the room‐temperature photoluminescence (PL). Samples were prepared by plasma enhanced chemical vapor deposition. The PL intensity increased by one order‐of‐magnitude after annealing for 20 min at 800 °C compared to that of the as‐deposited sample. We have followed the changes in the chemical microstructure of the materials byinsitureal‐time ellipsometry, and suggest that the annealing is characterized by two distinct mechanisms. The first is that hydrogen effusion from clustered hydrogen and/or =N–H bond breaking occurs in the first 5 min resulting in increasing dangling bond density and no increase in the PL intensity. The second occurs after longer annealing times due to local reconstruction of Si–O and Si–N bonds, rather than diffusional rearrangement of the atomic species. This results in a more dense material with a higher refractive index, fewer nonradiative recombination centers, and more efficient PL. A model is presented to describe both the radiative and nonradiative recombination processes. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115352

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Calibrated intensity noise measurements of microcavity lasers diodes are presented. Partition noise due to polarization degeneracy is found to render excess noise that destroys squeezing. The measurements indicate that it may be necessary to introduce polarization control to realize sub‐shot‐noise levels in microcavity laser diodes. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115353

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We report the characterization of a set of broad‐area semiconductor diode lasers with mid‐wave infrared (3–5 &mgr;m) emission wavelengths. The active region of each laser structure is a 5‐ or 6‐period multiple quantum well (MQW) with Ga0.75In0.25As0.22Sb0.78barriers and type‐II (broken‐gap) Ga0.75In0.25Sb/InAs superlattice wells. The cladding layers of each laser structure aren‐ andp‐type InAs/AlSb (24 A˚ /24 A˚) superlattices grown lattice‐matched to a GaSb substrate. By tailoring constituent layer thicknesses in the Ga0.75In0.25Sb/InAs superlattice wells, laser emission wavelengths ranging from 3.28 &mgr;m (maximum operating temperature=170 K) to 3.90 &mgr;m (maximum operating temperature=84 K) are obtained. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115354

出版商:AIP    

年代:1995

数据来源: AIP