摘要:

A graded superlattice composed of AlxGa1−xAs and GaAs having a total thickness of 150 A˚ was incorporated on each side of the active layer of an otherwise standard double heterojunction laser. In spite of no optimization, current threshold densities as low as 600 A/cm2at 880 nm were obtained in broad area devices with 300‐&mgr;m cavity lengths. Otherwise identical structures with abrupt heterointerfaces in place of a graded superlattice exhibited current threshold densities in the range 1.2–1.4 kA/cm2. Silicon and beryllium were used forn‐ andp‐type dopants. These results represent the best values for bulk laser and are attributed to improved interfaces primarily that between the bottom confining layer (substrate side) and the active layer.

ISSN:0003-6951    

DOI:10.1063/1.94588

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

Using a novel three‐pulse technique, essential information about the density, optical effective mass, and kinetics of laser‐generated plasmas in silicon has been obtained.

ISSN:0003-6951    

DOI:10.1063/1.94543

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

We report the generation of a stable single longitudinal mode in the transient spectrum of a GaAlAs laser diode using dispersive external feedback. The characteristics of the spectral evolution subsequent to a step increase in the drive current can be adequately understood from consideration of temperature induced shift of the gain spectrum and longitudinal modes as a function of time. Operation in a single longitudinal mode is observed from the first few nanoseconds out to steady state for lasers with both index guiding and gain guiding. Over 7 mW of single mode power is observed with an index‐guided laser.

ISSN:0003-6951    

DOI:10.1063/1.94552

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

This letter describes a computational technique for optimal control problems arising in the synthesis of electron and ion lenses. The method provides an effective search algorithm for electrostatic and/or magnetic imaging fields with minimum aberrations. An optimized electrostatic field distribution is given as an example of application.

ISSN:0003-6951    

DOI:10.1063/1.94559

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

The phase noise characteristics of single mode semiconductor lasers with optical feedback have been studied. A correlation is found between the suppression of the low‐frequency noise and the enhancement of the high‐frequency noise near the relaxation oscillation frequency. Contrary to previous analyses, the low‐frequency noise is minimized when the reflected light is 70°–90° out of phase with respect to that inside the diode laser cavity. A calculation of the laser frequency fluctuation spectrum, taking into account the amplitude‐phase coupling of the laser field, agrees with the observation. A new explanation is proposed for the feedback‐induced phase noise reduction effect.

ISSN:0003-6951    

DOI:10.1063/1.94573

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

A three‐segment laser, when separately pumped, shows both frequency switching and continuous tuning with a modulation current applied to the middle segment. The wavelength changes are attributed to gain peak shift with the carrier concentration and carrier‐induced index change. A total wavelength change of 61 A˚, a continuous tuning range of 4.1 A˚, and a tuning rate of −0.74 A˚/mA are obtained. The laser may be useful in optical FM fiber communication.

ISSN:0003-6951    

DOI:10.1063/1.94581

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

A new type of high‐speed optical modulator is proposed and demonstrated. An electric field is applied perpendicular to GaAs/GaAlAs multiple quantum well layers using a ‘‘p‐i‐n’’ diode doping structure of 4‐&mgr;m total thickness. The optical absorption edge, which is particularly abrupt because of exciton resonances, shifts to longer wavelengths with increasing field giving almost a factor of 2 reduction in transmission at 857 nm with an 8‐V reverse bias. The shifts are ascribed to changes in carrier confinement energies in the wells. The observed switching time of 2.8 ns is attributed toRCtime constant and instrumental limitations only, and fundamental limits may be much faster.

ISSN:0003-6951    

DOI:10.1063/1.94586

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

We report the fabrication of metal‐oxide‐semiconductor field‐effect transistors (MOSFET’s) in laser recrystallized silicon films on a lithium tantalate substrate with an intervening silicon dioxide layer. Deposited polycrystalline silicon films were irradiated with a scanning focused argon ion laser beam which caused melting and subsequent crystallization of the silicon film into crystallites suitable for MOSFET fabrication. Melting and recrystallization of the silicon film without damaging the substrate were accomplished by irradiation with 0.3–0.4 W of argon ion laser power focused to a 50‐&mgr;m‐diam spot. Transistor channel mobility was measured to be 50 cm2/Vs. When operated as integrated photodetectors, a responsivity of approximately 0.5 A/W was measured. Theoretical operation of these MOSFET’s as integrated photodetectors is derived and compared to observed operation.

ISSN:0003-6951    

DOI:10.1063/1.94587

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

An F2excimer laser at 157 nm has been used for the first time as an exposure source for high resolution photolithography. At this short wavelength, conventional glass and quartz mask substrates are opaque, and therefore alkaline‐earth halides and sapphire were used as mask substrates. The masks were patterned by electron beam lithography, and mask features as narrow as 150 nm have been replicated and represent the smallest features yet produced by contact photolithography.

ISSN:0003-6951    

DOI:10.1063/1.94589

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

The operation of the first optical parametric oscillator using a urea crystal is reported. Tunable radiation in both the visible and IR was obtained with conversion efficiencies as high as 20%.

ISSN:0003-6951    

DOI:10.1063/1.94590

出版商:AIP    

年代:1984

数据来源: AIP