摘要:

A repetitively pulsed, traveling‐wave laser has been operated with a front‐to‐back ratio exceeding 1000 : 1 when producing peak powers in excess of 3 MW.

ISSN:0021-8979    

DOI:10.1063/1.328087

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

A model which completely describes the Cu/CuCl double pulse laser is presented. The dissociation discharge pulse and afterglow are simulated and the results are used as initial conditions for an analysis of the pumping discharge pulse and laser pulse. Experimental behavior including the minimum, optimum, and maximum delays between pulses, and the dependence of laser pulse energy on dissociation energy are satisfactorily reproduced. An optimum tube temperature is calculated, and the dependence of laser pulse energy on tube temperature (i.e., CuCl vapor pressure) is explained for the first time.

ISSN:0021-8979    

DOI:10.1063/1.328088

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Active and passive mode locking of strip buried heterostructure lasers is observed using an external cavity consisting of a lens and a mirror. Using the second‐harmonic‐generation method to obtain the second‐order autocorrelation function we obtain Gaussian pulses as short as 35.7 psec (FWHM) at a 1.9‐GHz repetition rate. The optical spectrum of the mode locked laser consists of longitudinal modes of the composite cavity spaced by ∼0.05 A˚, whose amplitudes are modulated by the 2.09‐A˚‐mode spacing of the laser itself, and contained under a Gaussian envelope of 9.5‐A˚ FWHM. Additional very sharp structure (∼1.6‐psec FWHM) in the autocorrelation is shown to result from the presence of several laser mode groups.

ISSN:0021-8979    

DOI:10.1063/1.328089

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

We have observed laser action in single‐crystal ribbon whiskers of GaAs. The whiskers were grown with various dopants by a vapor transport process and were used, as grown, in an ultrashort cavity composed of high reflectivity dielectric mirrors. The structure was longitudinally photopumped, and it operated in a single mode at room temperature.

ISSN:0021-8979    

DOI:10.1063/1.328090

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

A new method for measuring absorption and gain spectra of lasers is presented. These spectra are deduced from measurements of spontaneous emission spectra at different laser currents supplemented by measurements of the laser line energy and the differential quantum efficiency. The spontaneous emission emerged from the side of the laser after traveling through a transparent cladding layer. At each current, the bias energyeVis determined. A simple theoretical model is used to converteVto minority carrier density. The method is based on the application of general relations between the rates of spontaneous emission, stimulated emission, and optical absorption. A new general proof of these relations is presented. The gain versus carrier density relation at the laser line energy is measured for four samples having different active layer doping or Al composition. Gain increased superlinearly with carrier density in undoped andn‐type samples and increased slightly sublinearly in ap‐type sample. The losses at low carrier densities ranged from 100–200 cm−1. For one undoped sample, the changes in the absorption edge caused by the electron and hole densities increasing from 5×1016to 1.1×1018cm−3were deduced by comparing the measured changes with a model calculation. It was found that the exponential broadening increased 20%, that the energy gap decreased 12–16 meV, and that the strength of optical absorption at low energies decreased by about a factor of 1.4.

ISSN:0021-8979    

DOI:10.1063/1.328091

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

The size of defects necessary to cause pulsations, in otherwise ideal semiconductor injection lasers, is calculated for two defect models: a nonradiative region and a number of nonradiative surfaces. The point of instability for pulsations is found by solving the linearized rate equations describing small oscillations about the steady state and determining the length of the nonradiative region or the number of surfaces for which damped oscillations change to growing oscillations. The validity of this method is verified by computer calculations of large amplitude pulsations in a particular case. An oscillating light intensity induces an oscillating component of gain. Part of the oscillating gain is in phase with the light intensity in the absorbing region, causing growth, and is directly out of phase in the amplifying region, causing damping. The laser pulsates if the in‐phase gain in the absorbing region is dominant. This component of gain is enhanced by a short nonradiative lifetime. This mechanism applies over a broad range of parameters with optimum values of about 0.06–0.10 nsec for the nonradiative lifetime and 1–2 mW for the laser power. The requirement for pulsations found in earlier studies of divided contact lasers, that the gain versus carrier density relationg(n) be nonlinear withdg/dngreater in the absorbing region than in the amplifying region, is not required for pulsations if the relaxation time is short. However, increaseddg/dnin the absorbing region greatly enhances the ability of a small defect to produce pulsations. Forg(n) increasing linearity withn, a defect at least 11 &mgr; long is needed to cause pulsations, whereas fordg/dntwice as great in the absorbing region as in the amplifying region, a defect only 4 &mgr; long can cause pulsations. The possibility of increaseddg/dnand absorption in the nonradiative region due to local heating is discussed. For optimum lifetime and surface recombination velocity, each nonradiative surface is approximately equivalent to a nonradiative region about 1/2 &mgr; in length. Accordingly, two nonradiative cleaved surfaces are insufficient to be the sole cause of pulsations.

ISSN:0021-8979    

DOI:10.1063/1.328092

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

The characteristics of an optical fiber external resonator in conjunction with (GaAl)As stripe geometry lasers are described. We have observed a 6–10% reduction in the threshold current and have obtained 150 ps pulses at gigahertz repetition rates. The fiber resonator has also been used to quench self‐pulsations in a (GaAl)As injection laser. In order to explain many of our results we have used a model that uses the conventional semiconductor rate equations modified by the addition of saturable electron traps and the effects of the external cavity. Our results predict many of the self‐locking effects observed in injection lasers operating in an external cavity. Furthermore, the degree of self‐locking will be a strong function of the external cavity length and the density of saturable absorbers.

ISSN:0021-8979    

DOI:10.1063/1.328093

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

A technique for the cancellation of background contribution to four‐wave mixing is proposed and demonstrated. The technique consists of the destructive interference of the background parametric waves produced by two samples that differ only in one or more properties of interest. This cancellation technique is applicable even when the background itself contains resonances in the frequency range of interest. Cancellation factors of 500 and higher were achieved using a double cell for liquid specimens. This technique is demonstrated using phenol water solution. It is shown that with full background the 1004‐cm−1phenol line can hardly be observed at 1% phenol concentration whereas the same line is easily observed when the background is cancelled even at 0.1% phenol concentration. This technique can also be used to extract the real and imaginary parts of the nonlinear susceptibility without the use of the Kramers‐Kronig relations. We have performed this calculation in the case of 5% phenol solution in water.

ISSN:0021-8979    

DOI:10.1063/1.328094

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Stimulated Raman scattering in liquid nitrogen was studied with a high repetition rate Nd : YAG laser. Severe distortions of the laser and Raman light beams were observed. These thermal‐blooming effects are the result of heating of the laser path by vibrational energy relaxation which changes the refractive index of the medium.

ISSN:0021-8979    

DOI:10.1063/1.328095

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Stimulated scattering induced by the longitudinal electric field of a pump wave is studied theoretically for the case of dense relativistic electron beams traveling in cylindrical metal waveguides. Two processes are examined. In one, the pump wave decays parametrically into a slow and a fast space‐charge wave. In the other, it decays into a slow space‐charge wave and a TM wave of the guide. The frequency characteristics and stimulated growth rates are given for each process, as a function of beam diameter, velocity, and density.

ISSN:0021-8979    

DOI:10.1063/1.328096

出版商:AIP    

年代:1980

数据来源: AIP