Single-frequency 1310-nm AlGaInAs-InP grating-outcoupled surface-emitting lasers

Single-frequency 1310-nm grating-outcoupled surface-emitting (GSE) semiconductor lasers with output slope efficiencies exceeding 0.1 mW/mA into multimode fibers, threshold currents below 22 mA, and >30-dB sidemode suppression ratios are reported. These GSE lasers consist of 500-/spl mu/m-long active ridges that excite one end of surface-emitting second-order outcoupling gratings with 200-/spl mu/m-long first-order distributed Bragg reflector gratings terminating the laser cavities at both ends. The grating outcouplers range from 10 to 50 /spl mu/m in length. These lasers have an open eye pattern for nonreturn-to-zero signals at 2.5 Gb/s into single-mode fibers. The full-width half-maximum far-field beam divergences range from 1.5/spl deg/ /spl times/ 8/spl deg/ to 5/spl deg/ /spl times/ 8/spl deg/.     

GaAs/AlGaAs quantum cascade microlasers based on monolithic semiconductor-air Bragg mirrors

Edge emitting GaAs-based quantum cascade microlasers at a wavelength of 9 /spl mu/m were realised by monolithic integration of photonic bandgap mirrors based on deeply etched air-semiconductor Bragg gratings. The shortest operating device with Bragg mirrors on both sides has a cavity length of 180 /spl mu/m.     

1.55-/spl mu/m AlGaInAs-InP laterally coupled distributed feedback laser

A novel 1.55-/spl mu/m AlGaInAs-InP laterally coupled (LC) distributed feedback (DFB) semiconductor laser is presented. Longitudinal feedback and lateral optical confinement are realized simultaneously by incorporating deep gratings etched with inductively coupled plasma technique. Stable single-mode operation with a sidemode suppression ratio over 45 dB has been demonstrated for the fabricated LC-DFB laser.     

Surface-emitting unstable-resonator lasers with integrated diffractive beam-forming elements

Grating-coupled surface-emitting semiconductor lasers have been integrated with focusing and spot array generating diffractive beam-forming elements. The lasers have an unstable resonator producing a 160-/spl mu/m-wide single spatial mode. The area of the outcoupler element is 160 /spl mu/m/spl times/240 /spl mu/m. For an outcoupler focusing at 500 /spl mu/m above the surface the spot size is 9 /spl mu/m/spl times/17 /spl mu/m The spot size is primarily limited by aberrations in the wavefront of the guided mode.     

MQW DBR lasers with monolithically integrated external-cavity electroabsorption modulators fabricated without modification of the active region

In this letter, we report the design and operation of multiple-quantum-well distributed Bragg reflectors (MQW DBR) lasers with monolithically integrated external-cavity electroabsorption (EA) modulators without modification of the active region fabricated using only a single growth step. Devices were fabricated with operating wavelengths of 1.06, 1.07, and 1.08 /spl mu/m, which are red-shifted from the material gain peak wavelength (/spl lambda/=1.05 /spl mu/m) by 100, 200, and 300 /spl Aring/, respectively. The /spl lambda/=1.06-/spl mu/m device has a continuous-wave (CW) threshold current of 16 mA and a slope efficiency of 0.09 W/A from the modulator facet, while the /spl lambda/=1.08 /spl mu/m device has a CW threshold current of 33 mA and a slope efficiency of 0.40 W/A from the modulator facet. The /spl lambda/=1.06-, 1.07-, and 1.08-/spl mu/m device exhibits an extinction ratio of /spl ges/20 dB at a modulator bias of 1.0, 1.4, and 2 V, respectively.     

GaInAsSb-AlGaAsSb distributed feedback lasers emitting near 2.4 /spl mu/m

We have investigated fabrication and characteristics of continuous wave (cw) GaInAsSb-AlGaAsSb distributed feedback (DFB) lasers in the 2.4-/spl mu/m range. Single-mode DFB emission is obtained without overgrowth by first order Cr-Bragg gratings on both sides of a laser ridge. The cw threshold currents for a cavity with a length of 800 /spl mu/m and a width of 4 /spl mu/m are around 30 mA. At 20/spl deg/C and at an injection current of 190 mA output powers of 8.5 mW were realized. Monomode emission with a side-mode suppression ratio (SMSR) of 33 dB has been obtained.     

Experimental verification of numerically optimized photonic crystal injector, Y-splitter, and bend

We present the experimental measurement of a photonic crystal (PhC) device comprising an injector, Y-splitter, and 60/spl deg/ bend. The complete device consists of a 9-/spl mu/m-long injector tapering down from 5 /spl mu/m into a triangular-lattice-of-holes single-line defect waveguide with period a=430 nm and 36.2% air filling factor (corresponding to a radius over period (r/a) ratio of 0.30), an optimized Y-junction, 60/spl deg/ bend and output injectors, with a total device footprint of 30 /spl mu/m. This is etched into a GaAs/AlGaAs heterostructure using chlorine/argon chemically assisted ion beam etching (CAIBE). An erbium-doped fiber amplifier (EDFA)-based source and Fabry-Perot technique are used to characterize the device. The device displays a bandwidth of approximately 110 nm in the 1.55 /spl mu/m window, and a transmission of 70% relative to the same length of 5-/spl mu/m-wide waveguide. This is compared with three-dimensional finite-difference time-domain (3-D FDTD) results, which have a bandwidth and transmission of 120 nm and 75%, respectively. The highlight of this paper is the close agreement of the numerically optimized complete microcircuit with its experimental equivalent, and the significant improvement in bandwidth over previous work on Y-junctions.     

A W-band InAs/AlSb low-noise/low-power amplifier

The first W-band antimonide based compound semiconductor low-noise amplifier has been demonstrated. The compact 1.4-mm/sup 2/ three-stage co-planar waveguide amplifier with 0.1-/spl mu/m InAs/AlSb high electron mobility transistor devices is fabricated on a 100-/spl mu/m GaAs substrate. Minimum noise-figure of 5.4dB with an associated gain of 11.1 dB is demonstrated at a total chip dissipation of 1.8 mW at 94 GHz. Biased for higher gain, 16/spl plusmn/1 dB is measured over a 77-103 GHz frequency band.     

Edge-emitting lasers with short-period semiconductor/air distributed Bragg reflector mirrors

We demonstrate a short-cavity edge-emitting 0.98-/spl mu/m GaAs-based laser with semiconductor/air distributed Bragg reflector (DBR) mirrors made by reactive ion etching (RIE). The dc and small-signal modulation properties of 100-/spl mu/m-long lasers have been measured and are characterized by I/sub th/=4.5 mA and f/sub -3dB/=30 GHz under pulsed conditions, respectively. The far-field pattern of light emanating from the DBR is also measured.     

Type-II interband cascade lasers in the 4.3-4.7-/spl mu/m wavelength region

Operation of type-II interband cascade lasers in the 4.3-4.7-/spl mu/m wavelength region has been demonstrated at temperatures up to 240 K in pulsed mode. These lasers fabricated with 150-/spl mu/m-wide mesa stripes operated in continuous-wave (CW) mode up to a maximum temperature of 110 K, with an output power exceeding 30 mW/f and a threshold current density of about 41 A/cm/sup 2/ at 90 K. The maximum CW operation temperature of 110 K is largely limited by the high specific thermal resistance of the 150-/spl mu/m-wide broad area lasers. A 20-/spl mu/m-wide mesa stripe laser was able to operate in CW mode at higher temperatures up to 125 K as a result of the reduced specific thermal resistance of a smaller device.     

VCO phase-noise improvement by gate-finger configuration of 0.13-/spl mu/m CMOS transistors

Using a standard logic process, 0.13-/spl mu/m RF CMOS devices with multifinger gate structure have been fabricated. The flicker noise and minimum noise figure characteristics have been investigated with different gate layout splits, where the device parasitic resistance is the determining factor in this issue. The stripe-shaped gate configuration demonstrates better noise performance, due to the reduction of device gate resistance. In addition, the MOS varactors designed with different gate layouts were used in a 5.2-GHz voltage-controlled oscillator (VCO) design, where the VCO with the stripe-shaped (2 /spl mu/m /spl times/ 36 fingers) gate varactor improved about 6 dB in phase-noise performance at 100-kHz offset frequency than that of square-shaped (8 /spl mu/m /spl times/ 9 fingers) gate varactor.     

GaAs MOSFET with oxide gate dielectric grown by atomic layer deposition

For the first time, a III-V compound semiconductor MOSFET with the gate dielectric grown by atomic layer deposition (ALD) is demonstrated. The novel application of the ALD process on III-V compound semiconductors affords tremendous functionality and opportunity by enabling the formation of high-quality gate oxides and passivation layers on III-V compound semiconductor devices. A 0.65-/spl mu/m gate-length depletion-mode n-channel GaAs MOSFET with an Al/sub 2/O/sub 3/ gate oxide thickness of 160 /spl Aring/ shows a gate leakage current density less than 10/sup -4/ A/cm/sup 2/ and a maximum transconductance of 130 mS/mm, with negligible drain current drift and hysteresis. A short-circuit current-gain cut-off frequency f/sub T/ of 14.0 GHz and a maximum oscillation frequency f/sub max/ of 25.2 GHz have been achieved from a 0.65-/spl mu/m gate-length device.     

High-performance 1.06-/spl mu/m selectively oxidized vertical-cavity surface-emitting lasers with InGaAs-GaAsP strain-compensated quantum wells

We present the first room-temperature continuous-wave operation of high-performance 1.06-/spl mu/m selectively oxidized vertical-cavity surface-emitting lasers (VCSEL's). The lasers contain strain-compensated InGaAs-GaAsP quantum wells (QW's) in the active region grown by metalorganic vapor phase epitaxy. The threshold current is 190 /spl mu/A for a 2.5/spl times/2.5 /spl mu/m/sup 2/ device, and the threshold voltage is as low as 1.255 V for a 6/spl times/6 /spl mu/m/sup 2/ device. Lasing at a wavelength as long as 1.1 /spl mu/m was also achieved. We discuss the wavelength limit for lasers using the strain-compensated QW's on GaAs substrates.     

Nonreciprocal Reflection-Beam Isolators for Far-Infrared Use

Magnetoplasma reflection-beam isolators for submillimeter-wave use are discussed in theory and experiment. The basic device uses the Kerr transverse magnetooptic effect (plane of polarization of the EM wave in the plane of incidence, which is perpendicular to a dc magnetic field) in InSb near room temperature. When the semiconductor slab is covered with a thin dielectric layer acting as a matching transformer, improved performance is predicted and observed at 337 /spl mu/m, and very efficient isolator performance is predicted for 118 /spl mu/m. Physical arguments are presented to explain the nonreciprocal phenomenon and lead to better device design.     

Sub-40 /spl mu/A continuous-wave lasing in an oxidized vertical-cavity surface-emitting laser with dielectric mirrors

Due to two improvements in cavity design, low-threshold lasing is achieved in oxidized vertical-cavity surface-emitting lasers incorporating upper dielectric distributed Bragg reflectors. Intracavity absorption is reduced by removal of a heavily p-type contact layer and the use of a low-loss MgF-ZnSe upper mirror. We report sub-100 /spl mu/A lasing for a 7-/spl mu/m diameter device, and sub-40 /spl mu/A lasing for a 3-/spl mu/m diameter device. The low-loss cavity design also allows for highly multimode operation at a low-bias current of 600 /spl mu/A in a detuned cavity.     

Characterization and modeling of AlGaN/GaN MOS capacitor with leakage for large signal transistor modeling

Dual mode AlGaN/GaN metal oxide semiconductor (MOS) heterostructure field-effect transistor (HFET) devices were fabricated and characterized. In HFET mode of operation the devices showed an f/sub t//spl middot/L/sub g/ product of 12GHz/spl middot//spl mu/m at Vgs=-2 V. The AlGaN devices showed formation of an accumulation layer under the gate in forward bias and a f/sub t//spl middot/L/sub g/ product of 6GHz/spl middot//spl mu/m was measured at Vgs=5 V. A novel piecewise small signal model for the gate capacitance of MOS HFET devices is presented and procedures to extract the capacitance in presence of gate leakage are outlined. The model accurately fits measured data from 45MHz to 10GHz over the entire bias range of operation of the device.     

Design for high-power single-mode operation from 2-D surface-emitting ROW-DFB lasers

Stable single-mode single-lobe operation to high powers is predicted for two-dimensional surface-emitting lasers, if second-order distributed feedback/distributed Bragg reflector (DFB/DBR) gratings are preferentially placed in the elements of a resonant-optical-waveguide array. Beside their usual functions (i.e., feedback and outcoupling), the gratings act as an effective array-mode selector due to different interaction with the gratings of different array modes. The in-phase array mode is strongly favored to lase around its (lateral) resonance due to better field overlap with DFB region and lower interelement absorption loss than for nonresonant array modes. For 20-element arrays with 700/600 /spl mu/m DFB/DBR gratings, emitting at /spl lambda/=0.98 /spl mu/m, high (/spl sim/100 A/cm/sup 2/) intermodal discrimination /spl Delta/J/sub th/ is obtained. /spl Delta/J/sub th/ is enhanced to /spl sim/225 A/cm/sup 2/ by introducing free-carrier absorption in the array-interelement regions.     

Active U-turn electrooptic switch formed in patterned holographic polymer-dispersed liquid crystals

We have developed an active U-turn device by spatially patterning two identical holographic polymer dispersed liquid-crystal gratings. In the field-OFF state, the holographic planes of both gratings are slanted such that the angle of the diffraction beam is beyond the total internal reflection angle of the air-glass interface. The diffraction beam is "trapped" in the device until diffracted by the second slanted grating. In the field-ON state, the holographic grating is "erased" and the incident beam propagates directly through the sample. The index modulation is determined to be 0.059 /spl plusmn/ 0.006 at 1.55 /spl mu/m. Low switching voltage and sub-millisecond response times are reported.     

1.5-/spl mu/m InGaAsP-InP slab-coupled optical waveguide lasers

We report the demonstration of high-power semiconductor slab-coupled optical waveguide lasers (SCOWLs) operating at a wavelength of 1.5 /spl mu/m. The lasers operate with large (4/spl times/8 /spl mu/m diameter) fundamental mode and produce output power in excess of 800 mW. These structures have very low loss (/spl sim/0.5 cm/sup -1/) enabling centimeter-long devices for efficient heat removal. The large fundamental mode allows 55% butt-coupling efficiency to standard optical fiber (SMF-28). Comparisons are made between SCOWL structures having nominal 4- and 5-/spl mu/m-thick waveguides.     

Mid-infrared (8.5 /spl mu/m) semiconductor lasers operating at room temperature

The room-temperature pulsed operation of a semiconductor laser emitting at 8.5 /spl mu/m is reported. This device is an optimized vertical transition quantum cascade (QC) laser. At 300 K the peak output power from a single facet is 15 mW, and the current density at threshold is /spl sim/8 kA/cm/sup 2/. The temperature dependence of the threshold current density is described by a high T/sub 0/ (107 K) in the 200-320 K temperature range.