摘要:

Broad‐area InGaAsP/InP lasers emitting at 1.55 &mgr;m have been fabricated from material grown by liquid phase epitaxy. The effects of different levels of zinc doping of the antimeltback layer combined with light doping (≤5×1017cm−3) of the InP cladding layers have been studied. Threshold current densities of 2.1–2.3 kA cm−2are found under a range of zinc‐doping levels. The quantum efficiencies are highest, approximately 19% per facet, when the antimeltback layer is undoped. With zinc doping, the quantum efficiencies drop by a factor of 2–3. Photoelectrochemical etching has been used to reveal thep‐njunction. The etching shows that the zinc doping yields an increase in the small scale variations in the placement and abruptness of thep‐njunction.

ISSN:0021-8979    

DOI:10.1063/1.334718

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

A new self‐aligned rib‐waveguide structure using a large optical cavity for high‐power single‐mode operation is presented. cw output powers of 40 mW are achieved with linear light‐current (L‐I) characteristics and single transverse and longitudinal modes. Over the temperature interval 10 to 60 °C, we find a typicalT0of 270 K. This laser is easily coupled to a single‐mode fiber and has been modulated to 2 GHz with only a 3‐dB loss in output power.

ISSN:0021-8979    

DOI:10.1063/1.334719

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The temporal compression of a KrF laser pulse in a plasma cell via Raman backscattering is a promising technique for obtaining pulse widths of relevance to laser‐driven fusion. It is shown that this technique can also serve as an effective means for cleaning the spatial modulations in a pump beam. When a spatially incoherent pump is compressed by an initially Gaussian Stokes pulse, the spatial nonuniformities in the pump are averaged out to yield a smooth, nearly Gaussian Stokes pulse. Strong modulations in the pump lead to less overlap with the Stokes pulse, thus indicating a compromise between compression efficiency and the amount of incoherency that can be tolerated in the input pump. It is argued, however, that for compressors operated in the saturated gain limit, with sufficiently long Stokes pulses, considerable beam cleaning can be achieved with little loss of efficiency.

ISSN:0021-8979    

DOI:10.1063/1.334720

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

In this paper we investigate the dependence of the mode suppression in coupled‐cavity semiconductor lasers on coupling junction parameters and cavity lengths. An effective mirror formalism is developed and combined with exact numerical analysis to explore the mode behavior across the entire relative cavity gain operating range of coupled‐cavity resonators. A gap coupling model is also presented which permits one to deduce the optimum gap spacing for best mode suppression, as well as the dependence of this optimum gap spacing on relative cavity lengths. Finally, the exact numerical analysis is combined with spectral gain roll‐off to explore the mode suppression of all modes of the system versus cavity lengths. Long‐long and long‐short geometries are shown to be desirable as well as some interesting new intermediate cavity length ratios. Calculations indicate that coupled‐cavity 1.55‐&mgr;m lasers with mode suppression in excess of 10 cm−1to both near in and repeat modes are realizable.

ISSN:0021-8979    

DOI:10.1063/1.334721

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The characteristics of a three‐mode coupling in a dielectric slab waveguide attached doubly periodic surface corrugations are investigated. The coupled‐mode equations governing the first‐order Bragg interactions of three TE modes are systematically derived with the help of perturbation procedure. For the case where the waveguide is symmetric and the three TE modes are lowest even modes, the coupled‐mode equations are solved to obtain the reflection and transmission characteristics of the periodic waveguide of finite length. The results are compared with those of the two related two‐mode couplings in a dielectric slab waveguide with a singly periodic surface corrugation.

ISSN:0021-8979    

DOI:10.1063/1.334722

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The operating characteristics and scaling parameters of a flashlamp‐pumped, 4‐m‐long IBr laser were investigated to further evaluate its potential as a solar‐pumped laser. A peak power of 3 kW/cm2at 2.7 &mgr;m was achieved at 4‐Torr IBr pressure. A gain of 0.07 m−1was measured at a maximum capacitor discharge energy of 4 kJ. The threshold input power necessary for lasing was found to decrease by a factor of 4 and the laser pulse width increased fourfold as the active gain length was increased from 1 to 4 m. A maximum pulse width of 120 &mgr;s was achieved with 10‐Torr argon diluent added to 4‐Torr IBr. Quenching of the excited state by the parent molecule was shown to be unimportant for pressures less than 4‐Torr IBr. An intrinsic efficiency in the range of 12% has been measured for flashlamp‐pumped IBr.

ISSN:0021-8979    

DOI:10.1063/1.334723

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

An ultrasonic optical modulator using an interdigital transducer operating at a liquid–solid boundary is described. The fundamental characteristics of the optical modulator are given for a combination of a He–Ne 0.63‐&mgr;m laser and water as an acousto‐optic material. The modulator consists of a piezoelectric ceramic plate with interdigital electrodes. The diffraction pattern can be varied by changing the voltage or the frequency of the electrical signal applied to the transducer. By using the voltage dependence of the first‐order diffraction peak, we demonstrate optical modulation.

ISSN:0021-8979    

DOI:10.1063/1.334724

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

It is known that the propagation characteristics of elastic waves are influenced by the nature of biasing stress distributions in the propagating medium. A knowledge of the magnitude of such effects plays an important role in improving the performance and long term aging characteristics of surface acoustic wave (SAW) devices. Generally, SAW devices employ thin platelike structures as the propagating medium of surface waves. The biasing deformation of such structures due to externally applied forces can be decomposed into extensional and flexural deformations which can have substantially different effects on the change in the time delay between two observations points. This paper describes a study of the fractional change in the time delay of surface waves due to the stress components in terms of which a general deformation can be expressed. The information on the biasing state of thin disks has been employed in a previously reported perturbation procedure for equations of motion for small dynamic field superposed on a static bias. Computational results have been obtained for fractional changes in the time delay of surface waves in crystalline quartz of various orientations and propagation directions due to many simple stress systems in thin disks. We have considered the cases of flexural deformation of rectangular plates due to cylindrical bending and disks subjected to normal pressures, as well as extensional deformation due to a pair of forces acting diametrically on a circular disk along various azimuthal angles. Experimental results have been obtained for the moment‐frequency effect on circular ST‐cut quartz disks and the force‐frequency effects on both singly, as well as doubly rotated quartz disks. Good agreement has been obtained between the theoretical predictions and experimental measurements.

ISSN:0021-8979    

DOI:10.1063/1.334725

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Temperature profiles in sufficiently narrow thin‐film conductors can be computed in a quasi‐one‐dimensional model. The model applies when the linewidth is less than a thermal decay length. We discuss the thermal decay length as a function of geometrical and material parameters and find that many practical cases satisfy the narrow stripe criterion. Fringing effects are included in the model. Three specific examples are discussed: (i) the temperature of an isolated stripe, including fringing, (ii) temperature profiles near junctions of narrow stripes, and (iii) temperature profiles at the junction of a narrow tap and a wide stripe. The simplicity of the model makes it convenient for the design of electromigration experiments, for programmable read‐only memory fusing current calculations, etc. Examples and graphs are given for the case of passivated aluminum on SiO2. The graphs are useful for estimation of thermal parameters without calculation.

ISSN:0021-8979    

DOI:10.1063/1.334726

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The radiative yield of dense, high‐temperature plasma mixtures has been studied theoretically for conditions typically attained in puffed‐gas implosions from high‐voltage pulse power generators. The mixtures are characterized using an equilibrium ionization/radiation model which calculates the self‐consistent state density populations of detailed level configurations by solving the complete set of atomic rate equations. In order to accurately model the quantitative line emission as well as the radiation spectrum from the plasma mixtures, detailed atomic models ofL‐ andK‐shell ion level structure and collisional processes in neon, argon, and krypton are employed; these models are described in detail. Specific mixtures reported on include neon/argon, argon/krypton, helium/argon, and helium/krypton. They are considered as compressed stationary plasmas, radiating at constant temperature and density (the time‐history of the implosion dynamics is neglected in this report). While no power amplification is detected in the optically thin approximation via the various mixtures, broadband spectral enhancement is demonstrated using various constituents.

ISSN:0021-8979    

DOI:10.1063/1.334727

出版商:AIP    

年代:1985

数据来源: AIP