摘要:

A GaInAsP/InP Fabry–Perot‐type buried‐heterostructure quantum well laser operating at 1.55 &mgr;m has been realized utilizing iron‐doped semi‐insulating InP around vertical mesas fabricated by reactive ion etching using methane and hydrogen. A maximum cw output power of 19 mW has been achieved on as‐cleaved chips of 300 &mgr;m length with a quantum efficiency of 21% per facet. Threshold currents lie between 20 and 25 mA. As low as 2 &OHgr; series resistance has been measured despite an ohmic contact area not exceeding that of the 2‐&mgr;m‐wide mesa. A 3 dB bandwidth of 7.5 GHz at 12 mW output power is obtained from the small‐signal frequency modulation measurements.

ISSN:0003-6951    

DOI:10.1063/1.105612

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

We have observed two‐wave mixing in semi‐insulating AlGaAs/GaAs multiple quantum well structures at wavelengths near the exciton absorption. The photorefractive index changes are caused by the Franz–Keldysh effect on quantum‐confined excitons. Photorefractive gains larger than 200 cm−1are obtained for the first time at wavelengths near 836 nm using stationary fringes and dc applied fields up to 5 kV/cm. The direction of energy transfer between the two beams is determined by the direction of applied electric field.

ISSN:0003-6951    

DOI:10.1063/1.105613

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

We have performed low‐temperature femtosecond pump and probe experiments on GaAs/AlAs type II and GaAs/AlGaAs type I multiple quantum wells of similar well sizes. The measurements are analyzed using a many‐body theory appropriate for both types of systems. It is found that the type I and type II nonlinearities are very similar at early times after excitation. However, the very fast (<1 ps) &Ggr; toXelectron scattering in the type II samples causes pronounced differences at later times, allowing the observation of hole relaxation in the type II samples.

ISSN:0003-6951    

DOI:10.1063/1.105614

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

A new type of log‐periodic antenna, the wire log‐spiral, has been designed and implemented on GaAs substrates with low‐temperature grown GaAs photoconductors. The new antenna is compared to two traditional antenna designs (log‐periodic and dipole) used for the detection of pulsed THz radiation.

ISSN:0003-6951    

DOI:10.1063/1.105615

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

We report the results of investigations on the transient heating and series resistance of a vertical‐microcavity surface‐emitting (VMSE) laser with an air‐bridge structure. Transient temperature broadening of the lasing spectrum and chirping of the current versus voltage characteristic are analyzed experimentally and theoretically. We believe that the experiments provide us valuable information on the severity of the heating problems in VMSE laser.

ISSN:0003-6951    

DOI:10.1063/1.105616

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

We have fabricated the first heterojunction phototransistor (HPT) on InP‐on‐Si. These phototransistors, based on the InP/GaInAs heterojunction, have optical gains as high as 125 A/W at 1300 nm and dark currents as low as 300 pA, for a 48×64 &mgr;m HPT. The bandwidth was determined from impulse photoresponse measurements to be 4.4 GHz. The intrinsic bandwidth was estimated from the zero bias capacitance (0.2 pf) to be as high as 16 GHz.

ISSN:0003-6951    

DOI:10.1063/1.105617

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

A high‐resolution laser spectroscopy method is used to analyze the time‐of‐flight (TOF) distribution of uranium atoms photoablated by a Nd:YAGQ‐switched laser in real time. The velocity distribution of an individual pulsed beam of ablated particles was derived from the TOF spectrum. The velocity of the neutral atoms ranged from 1 to 10 km/s in our experiments.

ISSN:0003-6951    

DOI:10.1063/1.105618

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

An experimental investigation was made of the motion of a cavitation bubble in the vicinity of a free surface in order to study an induced secondary cavitation during the bubble rebound. A bubble was produced by focusing a ruby laser into water, and its subsequent behavior was observed with a high‐speed camera. The deformable nature of both a bubble and a free surface becomes significant as the mutual distance between them is decreased. Immediately after bubble rebound, a secondary cavitation occurs at around zero dynamic pressure region which is developed in water between a rising free surface and a collapsing bubble, due to the local pressure reduction mainly caused by the interaction of expansion waves originated from the surface.

ISSN:0003-6951    

DOI:10.1063/1.105619

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

The results of numerical simulations of two high‐rate diamond growth environments (oxygen‐acetylene torch and dc arcjet) are reported. The calculations account in detail for boundary‐layer transport, gas‐phase chemistry, and gas‐surface chemistry. Diamond growth rates are calculated self‐consistently with the gas‐phase concentrations, using a recently proposed methyl growth mechanism. The calculated growth rates agree well with the measured values, indicating that this growth mechanism can account for both high‐ and low‐rate diamond growth.

ISSN:0003-6951    

DOI:10.1063/1.105620

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Ultrathin Si3N4films are characterized with Auger electron spectroscopy, spectroscopic ellipsometry (SE), and Raman spectroscopy (RS). It is shown that Ar+sputtering induces preferential nitrogen sputtering which causes problems in the determination of the interface location. Film thickness measurements with the nondestructive SE technique result in film thicknesses systematically larger than those calculated from the Auger sputter profiling, for films thinner than 100 A˚. Furthermore, analysis of the SE and RS data shows that the films are dense and stoichiometric while the stress induced by the Si3N4film on the Si substrate amounts to 2–3 kbar.

ISSN:0003-6951    

DOI:10.1063/1.105621

出版商:AIP    

年代:1991

数据来源: AIP