Improved CW operation of quantum cascade lasers with epitaxial-sideheat-sinking

First results on the epilayer-side mounting of quantum cascade (QC) lasers are presented. Operated in continuous-wave (CW) mode, these lasers are superior to substrate-bonded devices. The maximum CW temperature is raised by 20 K (up to 175 K), and, at comparable heat sink temperatures, the performance with respect to threshold current, output power, and slope efficiency is greatly improved for the epilayer-side mounted devices. QC-laser-specific mounting procedures are discussed in this letter, such as the high reflectivity coating of the back-facet and the front-facet cleaving after mounting. Modeling of the temperature distribution inside the QC laser shows a strong temperature gradient within the active waveguide core, which partly explains the still low maximum CW operating temperatures     

High-speed Schottky-barrier pMOSFET with f/sub T/=280 GHz

High-speed results on sub-30-nm gate length pMOSFETs with platinum silicide Schottky-barrier source and drain are reported. With inherently low series resistance and high drive current, these deeply scaled transistors are promising for high-speed analog applications. The fabrication process simplicity is compelling with no implants required. A sub-30-nm gate length pMOSFET exhibited a cutoff frequency of 280 GHz, which is the highest reported to date for a silicon MOS transistor. Off-state leakage current can be easily controlled by augmenting the Schottky barrier height with an optional blanket As implant. Using this approach, good digital performance was also demonstrated.     

Proton-bombardment formation of stripe-geometry heterostructure lasers for 300 K CW operation

A method of defining the active region of stripe-geometry junction lasers by proton-bombardment-induced high-resistivity layers is described. The method yields more reproducible mode patterns and lower threshold currents than the previously used oxide insulation. The improved lasers operated continuously at heat-sink temperatures up to 110°C.     

CW operation of semiconductor ring lasers

Semiconductor ring lasers have been fabricated in single quantum well material using electron-beam lithography and SiCl/sub 4/ dry etching. CW operation has been achieved in 84 mu m diameter rings at a threshold current of 24 mA. This low value makes the structure very suitable for monolithic integration in optoelectronic circuits.<>     

CW operation of GaInAsP stripe lasers

A quantitative investigation of the constraints on dc operation of GaInAsP stripe-geometry lasers at room temperature and above has been made. Laser pulse threshold current, its temperature sensitivity, electrical series resistance, and the thermal resistance of the bonded device are critical parameters in this respect. Sets of theoretical curves have been generated that allow expected de thresholds to be determined from the value of the pulsed threshold. Experimental results confirm the accuracy of the expressions. For GaInAsP lasers, the low values of T0reported in the literature (47-80 K) imply that both electrical series resistance and thermal resistance must be minimized in order to obtain stable dc operation over a reasonable temperature range in conventional oxide or proton isolated stripe structures. Both parameters are calculated theoretically for a range of structures. The calculations show that thermal runaway is sensitive to electrical resistance in the range1-10 Omegathis suggests an area where improvements are possible. To this end, the use of tunneling Schottky contacts to a ternary InGaAs p-capping layer has been developed to minimize contact resistance.     

High-power singlemode CW operation of 1.5 /spl mu/m-range quantum dot GaAs-based laser

Narrow ridge stripe lasers with metamorphic InAs/InGaAs quantum dots grown using molecular beam epitaxy on GaAs substrates emit in the 1.5 /spl mu/m wavelength range demonstrating a differential quantum efficiency of about 50%, singlemode operation, and maximum continuous-wave power of 220 mW limited by thermal roll-over. Absence of beam filamentation is demonstrated up to the highest power levels studied.     

CW operation of corner cavity semiconductor lasers

Etched facet semiconductor lasers have been fabricated and tested under CW operating conditions. The lasers consist of stripes formed by proton implantation, a total internal reflection (TIR) corner, and an output coupling facet. Devices with a variety of output coupling geometries were fabricated. Laser threshold currents and spectral characteristics were measured. Threshold current levels of devices with several different aperture sizes are compared to those of structures with standard Fabry-Perot reflectors     

Graded base type-II InP/GaAsSb DHBT with f/sub T/=475 GHz

The first demonstration of a type-II InP/GaAsSb double heterojunction bipolar transistor (DHBT) with a compositionally graded InGaAsSb to GaAsSb base layer is presented. A device with a 0.4/spl times/6 /spl mu/m/sup 2/ emitter dimensions achieves peak f/sub T/ of 475 GHz (f/sub MAX/=265 GHz) with current density at peak f/sub T/ exceeding 12 mA//spl mu/m/sup 2/. The structure consists of a 25-nm InGaAsSb/GaAsSb graded base layer and 65-nm InP collector grown by MBE with breakdown voltage /spl sim/4 V which demonstrates the vertical scaling versus breakdown advantage over type-I DHBTs.     

CW room-temperature operation of Y-junction semiconductor ring lasers

CW room-temperature lasing in Y-junction semiconductor ring lasers with radii as small as 50 mu m is reported. The dependence of the threshold current density on device dimensions is examined for radii in the range 50-200 mu m and for waveguide widths of 2-8 mu m. From these quantum-well devices, approximately 1 mW of CW single-frequency Te-polarised lasing output is obtained.<>     

Noncatastrophic degradation of GaAs lasers under CW operation

Three types of noncatastrophic degradation have been observed during CW life tests of GaAs injection lasers at 77°K. First, when operated submerged in liquid nitrogen, a comparatively rapid decrease occurs in the power output. This effect appears to be due to the liquid nitrogen environment and is reversible. This phenomenon has not been observed to start until the laser is energized, which suggests that it is due to fine polarizable particles in the liquid nitrogen which are attracted to the junction region. Second, some lasers have been operated on a cold finger in vacuum at current levels less than three or four times threshold for as long as 1000 hours with no significant change in output. The power outputs under such conditions weresimfrac{1}{3}watt. When the current was increased byeond three or four times threshold, however, the light output decreasedsimfrac{1}{2}in several hours, and this degradation was irreversible. Third, a cyclic variation in output occurs when a cold trap is not used; apparently this variation is due to an oil film being slowly deposited on the laser mirrors. This effect is not observed when precautions are taken to prevent the growth of the oil film.     

CW operation of monolithic arrays of surface-emitting folded-cavityInGaAs/AlGaAs diode lasers

A monolithic 0.84-cm² two-dimensional array of surface-emitting folded-cavity InGaAs/AlGaAs diode lasers was mounted junction up on a W/Cu microchannel heatsink and evaluated under continuous-wave (CW) operating conditions. Each laser in the array contained two upward-deflecting internal-cavity 45° mirrors which were etched using chlorine ion-beam-assisted etching, and two top-surface facets. The CW threshold current densities of different sections of the array were ⩽223 A/cm², while effective CW differential quantum efficiencies were ⩾30%. A CW output power of over 40 W was obtained from the entire array, while a current-limited output power density of 84 W/cm² with an average temperature rise of ~30°C was obtained from a quarter of the array     

Room-temperature CW operation of 1.3 ?m distributed-feedback GaInAsP/InP lasers

Distributed-feedback GaInAsP/InP lasers with a low threshold current emitting at 1.3 ?m have been successfully fabricated. A minimum CW threshold current of 66 mA was obtained at room temperature. The temperature coefficient of lasing wavelength was 1 ?/°C, which is about a fifth of that for Fabry-Perot lasers. A stable single longitudinal mode was obtained up to 52°C in a p-side-up configuration.     

Low-threshold CW operation of square-shaped semiconductor ring lasers (orbiter lasers)

The CW operation of square-shaped semiconductor ring lasers is demonstrated with a threshold current as low as 6 mA. The ring resonator consists of straight waveguides and four total reflection mirrors. The lasers are fabricated using Br/sub 2/ dry etching on an InGaAs/GaAs strained single-quantum-well graded-index separate-confinement heterostructure wafer. The low-threshold CW operation is due to the high differential gain of the wafer and the low-loss total reflection mirror.<>     

CW high-power single-mode operation of gain-guided stripe-geometry multiple-quantum-well lasers

Stripe-geometry multiple-quantum-well GaAs-GaAlAs lasers grown by MO-CVD are reported to operate fundamental spatial and longitudinal mode up to more than 40 mW CW.     

15-nm base type-II InP/GaAsSb/InP DHBTs with F/sub T/=384 GHz and a 6-V BV/sub CEO/

Type-II InP/GaAsSb/InP double heterojunction bipolar transistors (DHBTs) with a 15-nm base were fabricated by contact lithography: 0.73/spl times/11 /spl mu/m/sup 2/ emitter devices feature f/sub T/=384GHz (f/sub MAX/=262GHz) and BV/sub CEO/=6V. This is the highest f/sub T/ ever reported for InP/GaAsSb DHBTs, and an "all-technology" record f/sub T//spl times/BV/sub CEO/ product of 2304 GHz/spl middot/V. This result is credited to the favorable scaling of InP/GaAsSb/InP DHBT breakdown voltages (BV/sub CEO/) in thin collector structures.     

A 183 GHz f/sub T/ and 165 GHz f/sub max/ regrown-emitter DHBT with abrupt InP emitter

Small-area regrown emitter-base junction InP/In-GaAs/InP double heterojunction bipolar transistors (DHBT) using an abrupt InP emitter are presented for the first time. In a device with emitter-base junction area of 0.7 /spl times/ 8 /spl mu/m/sup 2/, a maximum 183 GHz f/sub T/ and 165 GHz f/sub max/ are exhibited. To our knowledge, this is the highest reported bandwidth for a III-V bipolar transistor utilizing emitter regrowth. The emitter current density is 6/spl times/10/sup 5/ A/cm/sup 2/ at V/sub CE,sat/ = 1.5 V. The small-signal current gain h/sub 21/ = 17, while collector breakdown voltage is near 6 V for the 1500-/spl Aring/-thick collector. The emitter structure, created by nonselective molecular beam epitaxy regrowth, combines a small-area emitter-base junction and a larger-area extrinsic emitter contact, and is similar in structure to that of a SiGe HBT. The higher f/sub T/ and f/sub max/ compared to previously reported devices are achieved by simplified regrowth using an InP emitter and by improvements to the regrowth surface preparation process.     

CW operation of a cleaved-coupled-cavity array of phase-locked GaAlAs lasers

Tunable single-longitudinal-mode operation has been obtained at power levels up to 50 mW from a continuously operating cleaved-coupled-cavity array of phase-locked diode lasers. In addition, conversion of a multilobed to a single-lobed radiation pattern was observed as a function of current supplied to the control segment of the coupled cavity.     

Operating characteristics of CW CO/sub 2/-N/sub 2/O laser

The authors have obtained the emission characteristics of a CW CO/sub 2/-N/sub 2/O laser. The CO/sub 2/ laser lines and N/sub 2/O laser lines vary according to the applied condition. Thus the operating conditions are interpreted.<>     

Theory and operation of high-power CW and long-pulse dye lasers

A complete theoretical model for CW and long-pulse dye lasers is developed. The effects of excited singlet-state absorption of pump and laser fight and triplet absorption of pump and laser light are included. Expressions are derived for gain, actual dye transmission, and output power. Experimental work is presented to verify the theory and to obtain values of excited-state absorption cross sections for rhodamine 6G by matching experimental to theoretical curves.     

LD泵浦微型YAG激光器的单模连续运转

本文报道了793nmLD泵浦YAG激光器TEM_(00)模的连续运转,描述了实验系统,给出了实验结果,讨论了模式匹配、光谱匹配、阈值功率和斜率效率等问题。