摘要:

Time‐dependent intensities of the spectral lines emitted by laser‐induced plasmas generated in several gases are presented. The time‐resolved and spatially varying intensities of two once‐ionized nitrogen lines were used to calculate radial temperature distribution of temperature within the plasma. A modified blast wave theory, in which ionization was included through the Saha equation and the equation of conservation of charge, was used to calculate time‐dependent intensities of several spectral lines of C, N, He, and Ar. The temporal profiles of the spectral lines appear to be dependent on the ionization potentials of the species in the plasma.

ISSN:0021-8979    

DOI:10.1063/1.346285

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Third‐harmonic generation (THG) was used to monitor ground‐state atomic hydrogen H(1s 2S1/2) in a dc plasma system. A 364.6 nm laser beam focused through H2or CH4/H2plasmas induced THG at 121.5 nm, near the atomic hydrogen 2p 2PoJ→1s 2S1/2Lyman‐&agr; transition. Both the intensity and frequency shift of the excitation spectra exhibited dependence on the plasma power. Absolute H atom concentration was estimated by comparing the frequency shift to that obtained in a calibrated microwave discharge flow system. The sensitivity was ∼4×1013cm−3(100 ppm). The measured atomic hydrogen densities were substantially less than in other diamond chemical vapor deposition methods and may explain the lower diamond deposition rates obtained with dc plasma systems of this type.

ISSN:0021-8979    

DOI:10.1063/1.346263

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The general approach to cylindrically symmetric force‐free magnetic fields first introduced by Lu¨st and Schlu¨ter [Z. Astrophys.34, 263 (1954)], is restricted to fields of the formH=[0,H&fgr;(r),Hz(r)], and subsequently used to determine a set of solutions to the force‐free field equations with nonconstant &agr;. The first element of the set is the well‐known constant &agr; solution of Lundquist [Ark. Fys.2, 361 (1951)]. These solutions may have practical applications with respect to high‐temperature superconductors.

ISSN:0021-8979    

DOI:10.1063/1.346264

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The performance characteristics of ridge waveguide In0.2Ga0.8As/GaAs multiquantum‐well lasers are reported. The lasers emit more than 50 mW/facet in the temperature range 20–100 °C in the fundamental transverse mode. The external differential quantum efficiency of 250‐&mgr;m‐long lasers is 0.4 mW/mA/facet. The internal optical loss is 14 cm−1. The optical gain is found to vary linearly with current. The increase in threshold current with increasing temperature in these lasers is primarily due to decreasing carrier lifetime (increased carrier loss) at high temperature. Increasing the heterobarrier height may further improve the high‐temperature performance of these devices.

ISSN:0021-8979    

DOI:10.1063/1.346265

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

A low‐loss, high‐intensity color modulator based on the dichroic‐mirror‐induced separation of the light into three color channels, modulated by polymer dispersed liquid‐crystal shutters, is described. The maximum contrast obtained with the light‐scattering‐based shutter is estimated and compared with experimental values. The quality of color reproduction of the modulator is presented in a standard 2D CIE diagram while the luminance is included in the 3D version with an incandescent lamp used as the light source. The white color is reconstructed by the modulator with an efficiency of 50%.

ISSN:0021-8979    

DOI:10.1063/1.346266

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Tin‐diffused GaAs layer samples, with mean concentrations larger than 1019cm−3, were obtained by irradiating with a ruby laser GaAs substrates covered with thin tin layers. Mobilities between 100 and 200 cm2/V s were obtained. Both carrier concentration and mobility decrease with increasing energy density. Strong segregation effects were observed in the samples processed with large energy densities.

ISSN:0021-8979    

DOI:10.1063/1.346267

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The temporal variation of the electron and current densities as well as the discharge voltage in a XeCl excimer laser discharge is studied as function of gas pressure and HCl+Xe concentration. The results show that independent of pressure and gas mix composition the electron drift velocity is a constant ofvd=(1.2±0.2)×106cm s−1. While in discharges containing only helium the current and electron density are independent of pressureP, both quantities vary asP0.6once Xe and HCl have been added. The results are examined considering the most important atomic reaction rates.

ISSN:0021-8979    

DOI:10.1063/1.346268

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The results of an experimental investigation to improve the performance of a discharge‐pumped iodine monofluoride laser are reported. Lasing was observed at 478.7, 484.7, 490.7, and 496.5 nm. Electrical measurements of the discharge characteristics permitted the energy flow in the circuit to be followed and laser efficiencies to be calculated. Parametric studies of gas mixtures were carried out. By optimizing several parameters, single‐pulse lasing energies greater than 50 mJ were obtained.

ISSN:0021-8979    

DOI:10.1063/1.346269

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The optical and magneto‐optical properties of weakly guiding single‐mode buried channel waveguides in substituted yttrium iron garnet have been investigated experimentally. The propagation constant difference &Dgr;&bgr; of the two coupled TE and TM modes, which is of particular interest for waveguide isolator application, is found to be strongly dependent on waveguide geometry. Measured results can be explained by the specific growth of the top cladding layer, which occurs into different crystallographic directions around the etched waveguide core. This leads to a local variation of the refractive index, which effects the guidance of light, and to a local variation of birefringence, which effects &Dgr;&bgr;. The measured variation of &Dgr;&bgr; is shown to be primarily caused by growth induced birefringence. It is demonstrated that &Dgr;&bgr; can be controlled to small values at selectable waveguide widths as required for waveguide isolator application simply by an appropriate setting of fabrication parameters.

ISSN:0021-8979    

DOI:10.1063/1.346270

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Be ions are implanted into Te‐doped Ga0.96Al0.04Sb layers grown by liquid‐phase epitaxy. Be distribution is analyzed from secondary‐ion mass spectrometry profiles and is found to be in good agreement with a computed simulation one. Hall‐effect measurements show a complete electrical activity of the Be‐implanted ions. Mesa devices are realized on the Ga0.96Al0.04Sbp+/Ga0.96Al0.04Sbn−/GaSb+system: Be implantation leads to good quality junctions exhibiting homogeneous multiplication.

ISSN:0021-8979    

DOI:10.1063/1.346271

出版商:AIP    

年代:1990

数据来源: AIP