Continuous-wave operation of GaInAs-AlGaAsSb quantum cascade lasers

We report on the demonstration of continuous-wave (CW) operation of GaInAs-AlGaAsSb quantum cascade (QC) lasers. By placing a 2.5-/spl mu/m-thick gold layer on both sides of the laser ridge to extract heat from the active region in the lateral direction, together with mounting the device epilayer down, we have achieved CW operation of GaInAs-AlGaAsSb QC lasers composed of 25 stages of active/injection regions. The maximum CW operating temperature of the lasers is 94 K, and the emission wavelength is around /spl lambda//spl sim/4.65 /spl mu/m. For a device with the size of 10/spl times/2000 /spl mu/m/sup 2/, the CW optical output power per facet is 13 mW at 42 K and 4 mW at 94 K. The CW threshold current density is 1.99 kA/cm/sup 2/ at 42 K, and 2.08 kA/cm/sup 2/ at 94 K, respectively.     

High-power continuous-wave operation of quantum-cascade lasers up to 60/spl deg/C

High-temperature high-power continuous-wave (CW) operation of high-reflectivity-coated 12-/spl mu/m-wide quantum-cascade lasers emitting at /spl lambda/ = 6 /spl mu/m with a thick electroplated Au top contact layer is reported for different cavity lengths. For a 3-mm-long laser, the CW optical output powers of 381 mW at 293 K and 22 mW at maximum operating temperature of 333 K (60/spl deg/C) are achieved with threshold current densities of 1.93 and 3.09 kA/cm/sup 2/, respectively. At 298 K, the same cavity gives a maximum wall plug efficiency of 3.17% at 1.07 A. An even higher CW optical output power of 424 mW at 293 K is obtained for a 4-mm-long laser and the device also operates up to 332 K with an output power of 14 mW. Thermal resistance is also analyzed at threshold as a function of cavity length.     

High-power ridge waveguide InGaAsN lasers fabricated with pulsed anodic oxidation

High-power InGaAsN triple-quantum-well strain-compensated lasers grown by metal-organic chemical vapor deposition were fabricated with pulsed anodic oxidation. A maximum light power output of 145 mW was obtained from a 4-/spl mu/m ridge waveguide uncoated laser diode in continuous-wave (CW) mode at room temperature. The devices operated in CW mode up to 130/spl deg/C with a characteristic temperature of 138 K in range of 20/spl deg/C-90/spl deg/C.     

Short wavelength (/spl lambda//spl sim/4.3 /spl mu/m) high-performance continuous-wave quantum-cascade lasers

We report continuous-wave (CW) operation of a 4.3-/spl mu/m quantum-cascade laser from 80 K to 313 K. For a high-reflectivity-coated 11-/spl mu/m-wide and 4-mm-long laser, CW output powers of 1.34 W at 80 K and 26 mW at 313 K are achieved. At 298 K, the CW threshold current density of 1.5 kA/cm/sup 2/ is observed with a CW output power of 166 mW and maximum wall-plug efficiency of 1.47%. The CW emission wavelength varies from 4.15 /spl mu/m at 80 K to 4.34 /spl mu/m at 298 K, corresponding to a temperature-tuning rate of 0.87 nm/K. The beam full-width at half-maximum values for the parallel and the perpendicular far-field patterns are 26/spl deg/ and 49/spl deg/ in CW mode, respectively.     

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.     

Room-temperature continuous-wave quantum cascade lasers grown by MOCVD without lateral regrowth

We report on room-temperature continuous-wave (CW) operation of /spl lambda//spl sim/8.2 /spl mu/m quantum cascade lasers grown by metal-organic chemical vapor deposition without lateral regrowth. The lasers have been processed as double-channel ridge waveguides with thick electroplated gold. CW output power of 5.3 mW is measured at 300 K with a threshold current density of 2.63 kA/cm/sup 2/. The measured gain at room temperature is close to the theoretical design, which enables the lasers to overcome the relatively high waveguide loss.     

Low-threshold high-T/sub 0/ 1.3-/spl mu/m InAs quantum-dot lasers due to p-type modulation doping of the active region

P-type doping is used to demonstrate high-To, low-threshold 1-3 /spl mu/m InAs quantum-dot lasers. A 5-/spl mu/m-wide oxide confined stripe laser with a 700-/spl mu/m-long cavity exhibits a pulsed T/sub 0/ = 213 K (196 K CW) from 0/spl deg/C to 80/spl deg/C. At room temperature, the devices have a CW threshold current of /spl sim/4.4 mA with an output power over 15 mW. The threshold at 100/spl deg/C is 8.4 mA with an output power over 8 mW.     

Electrically pumped room temperature CW VCSELs with 2.3 /spl mu/m emission wavelength

Continuous wave (CW) operation at room temperature of electrically pumped InGaAlAs/InP vertical-cavity surface-emitting lasers (VCSELs) at emission wavelengths as high as 2.3 /spl mu/m is demonstrated for the first time. Devices with 15 /spl mu/m active region diameter show a maximum output power of 0.75 mW at 20/spl deg/C and a maximum CW operating temperature of 45/spl deg/C.     

Low-threshold continuous-wave 1.5-/spl mu/m GaInNAsSb lasers grown on GaAs

We present the first continuous-wave (CW) edge-emitting lasers at 1.5 /spl mu/m grown on GaAs by molecular beam epitaxy (MBE). These single quantum well (QW) devices show dramatic improvement in all areas of device performance as compared to previous reports. CW output powers as high as 140 mW (both facets) were obtained from 20 /spl mu/m /spl times/ 2450 /spl mu/m ridge-waveguide lasers possessing a threshold current density of 1.06 kA/cm/sup 2/, external quantum efficiency of 31%, and characteristic temperature T/sub 0/ of 139 K from 10/spl deg/C-60/spl deg/C. The lasing wavelength shifted 0.58 nm/K, resulting in CW laser action at 1.52 /spl mu/m at 70/spl deg/C. This is the first report of CW GaAs-based laser operation beyond 1.5 /spl mu/m. Evidence of Auger recombination and intervalence band absorption was found over the range of operation and prevented CW operation above 70/spl deg/C. Maximum CW output power was limited by insufficient thermal heatsinking; however, devices with a highly reflective (HR) coating applied to one facet produced 707 mW of pulsed output power limited by the laser driver. Similar CW output powers are expected with more sophisticated packaging and further optimization of the gain region. It is expected that such lasers will find application in next-generation optical networks as pump lasers for Raman amplifiers or doped fiber amplifiers, and could displace InP-based lasers for applications from 1.2 to 1.6 /spl mu/m.     

Continuous-wave operation of GaInAsSb-GaSb type-II ridge waveguide lasers emitting at 2.8 /spl mu/m

We have realized compressively strained GaInAsSb-GaSb type-II double quantum-well lasers with an emission wavelength of 2.8 /spl mu/m. Using broad area devices, an internal absorption of 9.8 cm/sup -1/ and an internal quantum efficiency of 0.57 is determined. For the increase of the threshold current with temperature, a T/sub 0/ of 44 K is obtained. Narrow ridge waveguide lasers show continuous-wave laser operation at temperatures up to 45 /spl deg/C, with room-temperature (RT) threshold current of 37 mA. At RT, the maximum optical output power per facet of an uncoated 800/spl times/7 /spl mu/m/sup 2/ ridge waveguide laser exceeds 8 mW.     

Low-temperature optimized vertical-cavity lasers with submilliamp threshold currents over the 77-370 K temperature range

We demonstrate an extended temperature range (77-370 K) of continuous wave (CW) operation for dielectrically-apertured double-intracavity-contacted vertical-cavity InGaAs strained QW lasers optimized for operation at cryogenic temperatures. Superior performance is achieved through the alignment of the cavity mode with the gain of the first and second quantized subbands at 77 K and room temperature, respectively. This design results in submilliamp threshold currents over a 77-370 K temperature range for 5.4-/spl mu/m diameter lasers. The threshold is 120 /spl mu/A and the output power is >8 mW at 77 K.     

Ridge-width dependence on high-temperature continuous-wave operation of native oxide-confined InGaAsN triple-quantum-well lasers

InGaAsN triple-quantum-well (TQW) ridge waveguide (RWG) lasers were fabricated with contact ridge width of 4, 10, 50, and 100 /spl mu/m, respectively, using pulsed anodic oxidation (PAO). All these lasers worked under continuous-wave operation up to 100/spl deg/C. A clear trend of improved characteristic temperature (T/sub 0/) was observed as the ridge width narrowed. Proper choosing of ridge height and optimized PAO process were believed to minimize the lateral spreading current and reduce the scattering losses at the etched RWG sidewall, both of which are beneficial to the narrow ridge lasers operation. High output power of 298.8 mW, low transparency current density of 130 A/cm/sup 2//well, and high T/sub 0/ of 157.2 K were obtained from InGaAsN TQW 4-/spl mu/m-width lasers.     

Room-temperature low-threshold type-II quantum-well lasers at 4.5 /spl mu/m

We report optically pumped InAs-InGaSb-InAs-AlSb type-II quantum-well lasers at 3.84-4.48 /spl mu/m. Lasing was observed at temperatures up to 300 K with a characteristic temperature T/sub 0/ of 61.6 K. The average absorbed threshold power was only 0.7 mW at 220 K, and 2.7 mW at 300 K with a pulselength of 650 ns and a repetition rate of 2 kHz. At 49 K, the continuous-wave (CW) output power was 4.2 mW/facet with an absorbed threshold pump power of 31.5 mW and an absorbed pump power of 62 mW, indicating a differential quantum efficiency of 54% for two facets.     

Resonant-phonon terahertz quantum-cascade laser operating at 2.1 THz (/spl lambda//spl sime/141 /spl mu/m)

The development of quantum-cascade lasers (QCLs) at 2.1 THz (/spl lambda//spl sime/141 /spl mu/m), which is the longest wavelength QCL to date without the assistance of magnetic fields, is reported. This laser uses a structure based on resonant-phonon depopulation, and a metal-metal waveguide to obtain high modal confinement with low waveguide losses. Lasing was observed up to a heatsink temperature of 72 K in pulsed mode and 40 K in continuous-wave (CW) mode, and 1.2 mW of power was obtained in CW mode at 17 K.     

650-nm vertical-cavity surface-emitting lasers: laser properties and reliability investigations

650-nm AlGaInP-AlGaAs-based oxide-confined VCSELs are investigated in dependence on the current aperture size. VCSELs with small aperture (a=5 /spl mu/m) have a maximum continuous-wave (CW) output power of about 1 mW at room temperature. They reach higher operating temperatures (T/sub max/=55/spl deg/C), have narrower beam profiles, less transverse modes, and a higher side mode suppression compared to large aperture VCSELs (a>13 /spl mu/m). The latter devices emit a CW-output power P=3 mW at 20/spl deg/C. Reliability tests of 655-nm devices show at 20/spl deg/C an output power of P/spl ap/0.4 mW over more than 1000 h and at 40/spl deg/C P/spl ap/0.1 mW over 500 h.     

1.3-/spl mu/m Vertical-cavity surface-emitting lasers with double-bonded GaAs-AlAs Bragg mirrors

We demonstrate, for the first time, double-bonded AlGaInAs strain-compensated quantum-well 1.3-/spl mu/m vertical-cavity surface-emitting lasers (VCSELs). GaAs-AlAs Bragg mirrors were wafer-bonded on both sides of a cavity containing the AlGaInAs strain-compensated multiple-quantum-well active layers sandwiched by two InP layers. The lasers have operated under pulsed conditions at room temperature. A record low pulsed threshold current density of 4.2 kA/cm/sup 2/ and a highest maximum light output power greater than 4.6 mW have been achieved. The maximum threshold current characteristic temperature T/sub 0/ of 132 K is the best for any long wavelength VCSELs. The laser operated in a single-longitudinal mode, with a side-mode suppression ratio of more than 40 dB, which is the best results for 1.3-/spl mu/m VCSELs.     

Improved CW operation of GaAs-based QC lasers: T/sub max/= 150 K

We present a substantial improvement in the CW performance of GaAs-based quantum cascade lasers with operation up to 150 K. This has been achieved through suitable changes in device processing of a well-characterized laser. The technology optimizes the current injection in the laser by reducing the size of the active stripe whilst maintaining a strong coupling of the optical mode to preserve low current densities. The reduction of total dissipated power is critical for these lasers to operate CW. At 77 K, the maximum CW optical power is 80 mW, threshold current is 470 mA, slope efficiency is 141 mW/A, and lasing wavelength /spl lambda//spl sim/10.3 /spl mu/m.     

Low threshold high-power room-temperature continuous-wave operation diode laser emitting at 2.26 /spl mu/m

Diode lasers emitting at 2.26 /spl mu/m, based on the InGaAsSb-AlGaAsSb materials system, are reported. These devices exhibit high internal quantum efficiency of 78% and low threshold current density of 184.5 A/cm/sup 2/ for a 2-mm-long cavity. Output power up to 700 mW (/spl ap/550 mW) has been obtained at 280 K (300 K) in continuous-wave operation with 100 /spl mu/m/spl times/1 mm lasers. These devices have been coated with an antireflection on the output facet and are mounted epilayer down on a copper block. The working temperature was maintained by a thermoelectric Peltier cooling element.     

High-power single-mode antiresonant reflecting optical waveguide-type vertical-cavity surface-emitting lasers

Antiresonant reflecting optical waveguide (ARROW) techniques are employed in vertical cavity surface emitting lasers (VCSELs) to achieve high-power single-mode emission. Using the effective-index method and fiber mode approximation, the cold-cavity lateral modal behavior for the circular shaped ARROW VCSEL demonstrates significant reduction of radiation loss from that of a single antiguide, while maintaining strong discrimination against high-order modes. The circular-waveguide is created by selective chemical etching and two-step metal-organic chemical vapor deposition growth, with proton implantation used to confine the current injection to the low-index core region. A single-mode CW power of 7.1 mW has been achieved from an 8 /spl mu/m diameter ARROW device (index step /spl Delta/n = 0.05, emission at /spl lambda//sub 0/ = 980 nm) with a far-field FWHM of 10/spl deg/. Larger aperture (12 /spl mu/m) devices exhibit multimode operation at lower drive currents with a maximum single-mode continuous-wave output power of 4.3 mW.     

Room-temperature continuous-wave laser operation of electrically-pumped 1.55 /spl mu/m VECSEL

A report is presented on room-temperature (RT) continuous-wave (CW) laser emission at 1.55 /spl mu/m of an all InP-based electrically-pumped vertical external-cavity surface-emitting laser (EP-VECSEL). Threshold currents of 1.4 kA/cm/sup 2/ and output powers of up to 0.3 mW were measured under CW operation at RT. A maximum output power of 2.7 mW has been obtained in quasi-CW operation at a heatsink temperature of 10.5/spl deg/C. This first result demonstrates that EP-VECSELs are a potential candidate for the realisation of compact vertical-cavity emitting sources.