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.     

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.     

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.     

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.     

Ridge-width dependence on high-temperature continuous-wave quantum-cascade laser operation

We report continuous-wave (CW) operation of quantum-cascade lasers (/spl lambda/=6 /spl mu/m) up to a temperature of 313 K (40/spl deg/C). The maximum CW optical output powers range from 212 mW at 288 K to 22 mW at 313 K and are achieved with threshold current densities of 2.21 and 3.11 kA/cm/sup 2/, respectively, for a high-reflectivity-coated 12-/spl mu/m-wide and 2-mm-long laser. At room temperature (298 K), the power output is 145 mW at 0.87 A, corresponding to a power conversion efficiency of 1.68%. The maximum CW operating temperature of double-channel ridge waveguide lasers mounted epilayer-up on copper heatsinks is analyzed in terms of the ridge width, which is varied between 12 and 40 /spl mu/m. A clear trend of improved performance is observed as the ridge narrows.     

Continuous-wave operation of quantum cascade laser emitting near 5.6 /spl mu/m

Buried heterostructure quantum cascade lasers emitting at 5.64 /spl mu/m are presented. Continuous-wave (CW) operation has been achieved at -30/spl deg/C for junction down mounted devices with both facets coated. A 750 /spl mu/m-long laser exhibited 3 mW of CW power with a threshold current density of 5.4 kA/cm/sup 2/.     

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.     

Tunable twin-guide distributed feedback laser diodes with over 9 nm continuous electro-optic tuning range

Tunable twin-guide laser diodes at 1.55 /spl mu/m with a record electro-optic tuning range are presented. Employing an optimised device design, continuous tuning ranges of 9.3 and 11.0 nm are achieved in continuous-wave (CW) and pulsed operation, respectively. In CW operation, the output power of 300 /spl mu/m-long devices remains above 1 mW throughout the whole tuning range.     

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.     

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.     

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.     

Laser operation of epitaxially grown Yb:KLu(WO/sub 4/)/sub 2/--KLu(WO/sub 4/)/sub 2/ composites with monoclinic Crystalline structure

Epitaxial monoclinic double tungstate composites based on the strongly anisotropic KLu(WO/sub 4/)/sub 2/ (KLuW) were grown with high crystalline quality and laser operation of ytterbium was demonstrated for the first time. Highly efficient CW laser emission of an Yb:KLuW-KLuW crystal was achieved near 1030 nm. The 100-/spl mu/m-thick Yb:KLuW layer was pumped at wavelengths near 980 nm by a tapered diode laser as well as by a Ti:sapphire laser. More than 500 mW of CW output power and slope efficiencies up to 66% were obtained at room temperature without cooling.     

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.     

Highly reliable 60/spl deg/C 50-mW operation of 650-nm band window-mirror laser diodes

High-power GaInP QW laser diodes with a window-mirror-structure lasing at a wavelength of around 650 nm have been fabricated. The maximum light output power over 150 mW has been realized without optical mirror damage. In addition, the laser shows the fundamental-mode-operation at 50 mW and the dynamic characteristics sufficient for recordable digital versatile disc (DVD) applications. The lasers have been operating for 2000 h under the condition of CW, 50 mW, and 60/spl deg/C, for the first time.     

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.     

A continuous-wave hybrid AlGaInAs-silicon evanescent laser

We report a novel laser architecture, the hybrid silicon evanescent laser (SEL), that utilizes offset AlGaInAs quantum wells (QWs) bonded to a silicon waveguide. The silicon waveguide is fabricated on a silicon-on-insulator wafer using a complimentary metal-oxide-semiconductor-compatible process, and is subsequently bonded with the AlGaInAs QW structure using low temperature O/sub 2/ plasma-assisted wafer bonding. The optical mode in the SEL is predominantly confined in the passive silicon waveguide and evanescently couples into the III-V active region providing optical gain. The SEL lases continuous wave (CW) at 1568 nm with a threshold of 23 mW. The maximum temperature for CW operation is 60/spl deg/C. The maximum single-sided fiber-coupled CW output power at room temperature is 4.5 mW.     

160/spl deg/C pulsed laser operation of AlGaInP-based vertical-cavity surface-emitting lasers

Pulsed lasing operation of a 670 nm AlGaInP-based oxide-confined vertical-cavity surface-emitting laser (VCSEL) at high temperatures is demonstrated. At +120/spl deg/C heatsink temperature output power exceeded 0.5 mW and at +160/spl deg/C 25 /spl mu/W output power was achieved     

Pulsed operation of long-wavelength (/spl lambda//spl sime/11.3 /spl mu/m) MOVPE-grown quantum cascade lasers up to 350 K

Pulsed laser action above room temperature at /spl lambda//spl sime/11.3 /spl mu/m has been achieved in quantum cascade devices grown by metal organic vapour phase epitaxy (MOVPE). The emission wavelength (/spl lambda//spl sime/11.3 /spl mu/m) is the longest reported for QC lasers grown with this technique. The peak output power at 77 K is approximately 315 mW, decreasing to /spl sime/100 mW at room temperature. The devices display laser operation up to at least 350 K.     

High-power 1.02 mu m InGaAs/AlGaAs strained quantum well lasers with GaInP buried waveguides for pumping Pr/sup 3+/-doped optical fibre amplifier

High power 1.02 mu m single spatial mode laser diodes with low-loss (3.3 cm/sup -1/) GaInP buried waveguides have been developed for pumping Pr/sup 3+/-doped optical fibre amplifiers. A maximum CW light output power of 415 mW and an optical fibre output of 71 mW at 200 mA have been achieved. A preliminary lifetest showed stable operation for over 2300 h under 100 mW CW conditions at 50 degrees C.<>     

Vertical-cavity surface-emitting lasers in the 8-/spl mu/m midinfrared spectral range with continuous-wave and pulsed emission

Continuous-wave (CW) as well as pulsed-laser emission from a midinfrared (/spl lambda/=7.92 /spl mu/m) IV-VI vertical-cavity surface-emitting laser at 1.8 K is presented. The high-finesse microcavity, containing PbSe as an active medium, was optically pumped with a carbon monoxide laser at a wavelength of 5.28 /spl mu/m (1894 cm/sup -1/) in either CW or Q-switched mode. The maximum achieved CW power was 4.8 mW and pulsed peak powers were up to 23 W. Linewidths are considerably narrower than 0.10 cm/sup -1/, corresponding to 0.6 nm.