摘要:

The structure of defects occurring in degraded 1.3‐&mgr;m double‐channel planar buried heterostructure type laser diodes was studied in detail by conventional diffraction contrast, weak‐beam dark‐field microscopy and high‐resolution lattice imaging in a transmission electron microscope. The electrical activity of the defects was analyzed by means of the electron‐beam‐induced current. Device degradation is associated with the presence of interstitial Frank partial dislocation loops with a Burgers vector of (a/3) {111} at the interfaces between the InGaAsP active layer exposed after the channel etching and the firstp+‐InP layer of the liquid‐phase‐epitaxy‐grown current‐blocking layers. No other types of defects were observed in the course of the present study. The implications of the latter finding are far‐reaching and lead to a new degradation model for the microstrctural changes associated with the gradual degradation of long‐wavelength lasers. A new degradation model is proposed, and laser diode design considerations for degradation‐free operation are given. These consdierations are twofold: the device structure should (a) not favor Frank partial dislocation loop nucleation and (b) suppress the dissociation of the Frank partial dislocations.

ISSN:0021-8979    

DOI:10.1063/1.344999

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

We present a theoretical model of a physically pixellated nonlinear interference filter illuminated by a Gaussian laser beam. The plane‐wave model figure of merit of a previous paper is redefined as a function of spot size, pixel dimensions, and the thermal conductivities of the pixel and substrate. We present detailed calculations of switching powers, and actual values are obtained for the cases of glass and polyimide pixels on a sapphire substrate. The theory predicts that switching powers of the order of less than 1 mW can be achieved for the polyimide‐sapphire combination and 10 mW for the glass‐sapphire combination. An upper limit of the order of 107gate Hz/cm2in an array of pixels is projected.

ISSN:0021-8979    

DOI:10.1063/1.345000

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

A simulation code for an electron‐beam‐excited XeF(B→X) laser using Ar/Xe/F2gas mixtures is described. The validity of the code was checked by comparing the computed results to those obtained in a previously reported experiment with a 65‐ns, 1.14‐MW/cm3excitation pulse. Good agreement is demonstrated for sidelight fluorescence, laser waveforms, output power, and energy. Furthermore, the simulation code analysis suggests that the XeF laser can be operated effectively with low‐pressure (<1 atm) Ar/Xe/F2mixtures at room temperature. A maximum intrinsic efficiency of ∼3% is obtained at a total pressure of 0.5 atm. Such a low‐pressure Ar/Xe/F2laser gas mixture would permit operation of a scaled‐up XeF laser system since the intrinsic efficiency is as high as that with conventional high‐pressure (∼3 atm) Ne/Xe/NF3mixtures.

ISSN:0021-8979    

DOI:10.1063/1.345001

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

A modified amplified spontaneous emission technique has been introduced to measure the radial distributions of the gain and the saturation energy density of the output of a double‐discharge pulsed CuBr laser. An asymmetric distribution of the gain was obtained. With the laser tube temperature at 420 °C, the peak value of the gain and the saturation energy density are 70 db/m and 85 &mgr;J/cm3, respectively.

ISSN:0021-8979    

DOI:10.1063/1.345002

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The fabrication, performance characteristics, and design rules of buried-facet optical amplifiers are described. Chip gain of 25 dB, gain ripple of <1 dB, and gain difference of ≤1 dB for TE- and TM-polarized light are observed. The gain ripple and polarization dependence of gain correlate well with the ripple and polarization dependence of the amplified spontaneous emission spectrum. The performance of buried-facet amplifiers is comparable to that of cleaved-facet amplifiers with very good antireflection (R<10−4) coatings. The buried-facet design reduces the requirement on antireflection coatings and makes the fabrication process more reproducible.

ISSN:0021-8979    

DOI:10.1063/1.345003

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

A scaling up of kW‐class chemical oxygen‐iodine laser (COIL) is achieved. The key issues for the system design of COIL for industrial application is discussed. The scaled up COIL system of 1‐kW output power is now under trial operations. In these operations, a maximum output power of 1100 W, and a continuous operation time of more than 2 h with a power of over 500 W is recorded.

ISSN:0021-8979    

DOI:10.1063/1.345004

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Amplification of short pulse KrF lasers is theoretically studied by using both coherent and incoherent interaction models, which consist of five vibrational levels in the upper laser state and a single repulsive lower laser state. The multilevel models predict a significant decrease in the saturation energies for short applied laser pulses. When the laser pulse width is extremely short (≤1 ps), the higher vibrational levels in the upper KrF laser state are repumped from the lower laser state instead of being extracted by the laser pulse. Since the small‐signal gain also decreases as the applied pulse width decreases, due to mismatch between the laser pulse and the KrF gain spectrum, the energy extraction efficiencies for subpicosecond laser pulses deteriorate significantly. For longer pulse widths (≥10 ps), population repumping from the KrF(C) state increases the effective saturation energy of the KrF(B) state. A steady‐state population of ≊28% relative to the B‐state population is estimated for the C state from recent experimental results of KrF gain recovery.

ISSN:0021-8979    

DOI:10.1063/1.345005

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Proton‐exchanged waveguides fabricated in LiNbO3doped with 4.5% MgO and 0.1–0.2 % Nd:4.5% MgO have been characterized by prism‐coupling and infrared‐absorption spectroscopy. Single and multimode doped waveguides have temporally stable effective mode indices, and the refractive‐index profiles are identical to those observed for proton exchange in congruent LiNbO3. Effective diffusion coefficients for proton exchange in dopedxandz‐cut substrates have been estimated for waveguide‐fabrication temperatures in the range 182–235 °C. While diffusion coefficients for MgO:LiNbO3and Nd:MgO:LiNbO3appear to be identical, waveguides formed in the doped substrates have substantially smaller diffusion coefficients compared to waveguides formed in congruent LiNbO3, the magnitudes being down by as much as 50% forx‐cut waveguides and 37% forz‐cut waveguides. These results should prove of value when using the proton‐exchange technique to design waveguide lasers in Nd:MgO:LiNbO3.

ISSN:0021-8979    

DOI:10.1063/1.345006

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Atomic absorption spectroscopy has been used to determine Li+concentrations in benzoic acid after proton exchange withx‐ andz‐cut LiNbO3as a function of exchange time and temperature. The atomic absorption results, in agreement with our previous infrared spectroscopic and optical waveguide measurements, indicate that there is no evidence for saturation of the melt by Li+at typical melt volumes.

ISSN:0021-8979    

DOI:10.1063/1.345007

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

As is the case with the usual free‐electron laser with a helical magnetic field, the uniform magnetic‐field free‐electron laser has both the fundamental and the higher harmonic‐frequency (spontaneous and stimulated) emission, where, however, emission with higher harmonic frequencies occurs only off axis. (Thezcomponent of the initial electron velocity defines the axis direction, which is also the direction of the uniform magnetic fieldB.) Here, within the multiphoton formalism, using both the ordinary and scalarized photons, we study only the spontaneous emission, into the fundamental and higher harmonic frequencies. It is proven that the use of the scalarized photons, whose advantage is that they simplify many calculations, is generally equivalent to the use of the ordinary photons. Specifically we find that the radiated energy, either total or partial (for a particular harmonic), scales linearly withL, the interaction length, and quadratically withB. The numerical analysis of the angular distribution of the spontaneously emitted energy indicates that, in addition to dominant on‐axis fundamental frequency spontaneous emission, we can have rather significant higher harmonic‐frequency spontaneous emission occurring just slightly off axis. So it appears that, at least in principle, not only on axis but also slightly off axis (higher harmonic) spontaneous emission could be used to stimulate emission from electrons further along for sufficiently wide electron beams.

ISSN:0021-8979    

DOI:10.1063/1.345008

出版商:AIP    

年代:1990

数据来源: AIP