摘要:

Spatial hole burning causes rapid mode jumping and spectral broadening in free‐running long linear Nd3+‐fiber lasers. Phase modulators at either end of the resonator, operating in antiphase, provide active spatial averaging and permit stable single‐mode operation with a short‐term linewidth of ≊5 kHz at 1088 nm wavelength.

ISSN:0003-6951    

DOI:10.1063/1.104909

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Strained In0.2Ga0.8As/GaAs multiple quantum well polyimide buried ridge waveguide lasers with 3 dB bandwidths of 20 GHz andKfactors as low as 0.17 ns have been fabricated. This is the highest bandwidth and the lowestKfactor reported to date for quantum well lasers in any material system or for lasers of the ridge waveguide geometry.

ISSN:0003-6951    

DOI:10.1063/1.104910

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Generation of single pulses from a copper bromide laser with 2 ns pulse width is described here. At 11 kHz the pulse repetition rate, the stability of the amplitude, and the pulse width of these pulses are excellent. Theoretical considerations of the pulse shortening are also shown to agree well with the experiment.

ISSN:0003-6951    

DOI:10.1063/1.104911

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

We have studied the effect of nonuniformity in graded index, channel waveguide dimensions on the phase‐matching condition for guided‐wave nonlinear frequency conversion. Both theoretical and experimental results using normalized waveguide parameters and quasi‐phase matching for second‐ harmonic generation in annealed proton‐exchanged LiNbO3waveguides show the existence of an optimum waveguide design which is insensitive to inhomogeneities in the waveguide dimensions. Application of such a waveguide design using normalized approach can significantly relax the fabrication tolerance, leading to nonlinear guided‐wave devices with long interaction lengths and useful conversion efficiencies.

ISSN:0003-6951    

DOI:10.1063/1.104912

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

An apparent transition between active and nonactive second‐harmonic generation (SHG) has been discovered in the NaNb3O8solid solutions with the tetragonal tungsten bronze structure. No SHG was detected in 0.35Na2O:Nb2O5solid solution crystal or its powder. Nevertheless, powder SHG with a magnitude comparable to KH2PO4was observed when a small amount of Nb2O5was added to the powder ground from the crystal and sintered again. Microcracks and ferroelectric domain boundaries have been observed in the crystal using transmission electron microscopy. The only difference between the lattice images of SHG active powder and non‐SHG active powder is the absence of microcracks and ferroelectric domain boundaries in the SHG active powder. Dielectric constant of the 0.35Na2O:Nb2O5crystal is about 300 and &dgr; is 0.003 for frequency from 120 kHz to 12 MHz.

ISSN:0003-6951    

DOI:10.1063/1.104913

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Strained‐layer In0.35Ga0.65As‐GaAs‐AlGaAs graded index separate confinement heterostructure multiple quantum well lasers were grown by molecular beam epitaxy and processed as ridge waveguide structures. Devices with 3 &mgr;m×200 &mgr;m cavities have threshold currents of 18 mA (3000 A/cm2) and optical waveguide losses of 4.2 cm−1. The microwave modulation bandwidth of a 3 &mgr;m×200 &mgr;m device was determined to be 19.5 GHz, which exceeds the 15.5 GHz reported for multimode index‐guided devices, and is the highest direct modulation bandwidth reported for a quantum well laser.

ISSN:0003-6951    

DOI:10.1063/1.104914

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

We investigate enhanced and inhibited spontaneous emission effects in a vertical &lgr;‐microcavity structure havingtwokinds of quantum wells (QWs) with the thicknesses of 76 and 114 A˚, measuring both photoluminescence intensity and carrier lifetime. The 76 and 114 A˚ QWs are placed at the maximum and at the nodes of the emitted standing wave in the microcavity, respectively. When the &lgr;‐microcavity mode is tuned to the quantized band‐gap energy of the 76 A˚ QWs (enhanced condition), the PL intensity is enhanced compared with the case that the cavity mode is tuned to the quantized band‐gap energy of the 114 A˚ QWs (inhibited condition). In addition, the increase of the carrier lifetime is also observed under the inhibited condition. These results demonstrate existence of enhanced and inhibited spontaneous emission effects in the microcavity structures.

ISSN:0003-6951    

DOI:10.1063/1.104918

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Vertical cavity surface‐emitting lasers are integrated with GaAs/AlGaAs heterojunction phototransistors to yield optically controlled lasers. The two‐terminal device operates in several modes: As an amplifier with a large signal, external optical gain of 5, as in optical logic gate, and as an optically or electrically triggerable latch. The optical AND gate has an output on‐to‐off ratio of 10:1. Although the device has no optical feedback, latching is achieved with appropriate biasing through impact ionization. The device structure is advantageous for forming large two‐dimensional arrays for optical signal processing.

ISSN:0003-6951    

DOI:10.1063/1.104919

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Brillouin scattering from two classic glass‐forming materials, ZnCl2and glycerol, reveals a maximum in the ratio (&ggr;) of specific heatsCpandCvas a function of temperature. We propose that the temperature at which the maximum in &ggr; occurs in our materials may be indicative of a ‘‘liquid‐like’’ to ‘‘solid‐like’’ transformation. As such it may be a convenient thermodynamic signature of a ‘glass’ transition.

ISSN:0003-6951    

DOI:10.1063/1.104920

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

For chamber base pressure ≊5×10−4mbar in a rapid thermal processing chemical vapor deposition system, a 900 °C H2prebake for 60 s results in relatively high defect densities in the GexSi1−xepitaxial layer due to surface damage caused by the H2prebake. We have demonstrated that a very low thermal budgetinsitupreclean (800 °C/15 s) can reduce the defect densities. In addition, the use of a Si buffer layer grown at 1000 °C for 60 s prior to the GexSi1−xgrowth is capable of significantly reducing defect densities.

ISSN:0003-6951    

DOI:10.1063/1.104893

出版商:AIP    

年代:1991

数据来源: AIP