High Temperature Continuous-wave Operation Research Articles

High-temperature continuous-wave operation of InAs-based interband cascade laser

In this work, we report an InAs-based interband cascade laser that emits at λ = 4.58 μm in continuous-wave mode up to a maximum temperature of 64 °C, an increase of 29 °C beyond the previously highest reported value for InAs-based interband cascade lasers. At T = 20 °C, an output power of 20 mW was achieved for a 10-μm × 2-mm ridge waveguide device with one facet coated for high reflection and epilayer-down mounting.

High-temperature continuous-wave operation of 1310 nm InAs/GaAs quantum dot lasers

Here we report 1.3 μm electrical injection lasers based on InAs/GaAs quantum dots (QDs) grown on a GaAs substrate, which can steadily work at 110 °C without visible degradation. The QD structure is designed by applying the Stranski–Krastanow growth mode in solid source molecular beam epitaxy. The density of InAs QDs in the active region is increased from 3.8 × 1010 cm−2 to 5.9 × 1010 cm−2. As regards laser performance, the maximum output power of devices with low-density QDs as the active region is 65 mW at room temperature, and that of devices with the high-density QDs is 103 mW. Meanwhile the output power of high-density devices is 131 mW under an injection current of 4 A at 110 °C.

High-temperature continuous-wave operation of directly grown InAs/GaAs quantum dot lasers on on-axis Si (001)

Laser devices for silicon photonics are expected to be implemented in an integrated environment to complement CMOS devices. For this reason, quantum dot (QD) lasers with excellent thermal properties have been considered as strong candidates for Si photonics light sources. The direct growth of QD lasers on Si (001) on-axis substrates has been garnering attention owing to the possibility of monolithic integration on a CMOS-compatible wafer. In this paper, we report on the high-temperature (over 100°C) continuous-wave operation of an InAs/GaAs QD laser directly grown on on-axis Si (001) substrates through the use of only molecular beam epitaxy.

High power and high temperature continuous-wave operation of distributed Bragg reflector quantum cascade lasers

High temperature continuous-wave (CW) operation of a distributed Bragg reflector (DBR) quantum cascade laser is demonstrated up to a heat sink temperature of 80 °C. A CW output power of 2 W and a single mode operation with side mode suppression ratio of 30 dB around wavelength of 4.48 μm were achieved at 20 °C. The maximum pulsed and CW wall-plug-efficiencies reached 14.7% and 10.3% at 20 °C, respectively. A large tuning range of 5 cm−1 between mode hopping was observed and attributed to the thermal cross-talk from the gain section to the DBR section.

High-Power High-Temperature Continuous-Wave Operation of Quantum Cascade Laser at λ∼4.6 μm without Lateral Regrowth

High-power quantum cascade lasers (λ = 4.6 μm) working in continuous wave (cw) up to 90°C are presented. The material was grown by solid-source molecular beam epitaxy and processed into narrow conventional ridge geometry without lateral regrowth. High cw output power of 850mW at 10°C and more than 200mW at 90°C were obtained with threshold current densities of 1.34 and 2.47 kA/cm2, respectively, for a high-reflectivity-coated 12-μm-wide and 3-mm-long laser.

High-temperature continuous-wave operation of low power consumption single-mode distributed-feedback quantum-cascade lasers at λ∼5.2 μm

Continuous-wave operation of a distributed-feedback quantum-cascade laser in a packaged module is demonstrated up to a heat sink temperature of 80 °C with an output power of greater than 10 mW and a power consumption of less than 3.8 W. Single longitudinal mode emission near 5.24 μm is observed over a temperature range from 10 to 80 °C with a side mode suppression ratio greater than 20 dB limited by the instrumentation. A single spatial mode is determined with far-field pattern measurement. The above performance is achieved using a buried heterostructure and a small cavity of 7.6 μm×1.5 mm.

High-Temperature Continuous-Wave Operation of GaInAsN–GaAs Quantum-Dot Laser Diodes Beyond 1.3 $\mu$m

Internal laser parameters and characteristic temperature T0 of a GaInAsN-GaAs quantum-dot (QD) laser emitting above 1350 nm were determined. Continuous-wave operation of GaInAsN-GaAs QD ridge waveguide laser diodes with an emission wavelength of 1355 nm at room temperature (RT) is reported for the first time. Low threshold currents of 16 mA are achieved at RT. Ground state laser emission is observed up to temperatures of 75degC with a resulting laser emission wavelength of 1395 nm.

High-temperature continuous wave operation of strain-balanced quantum cascade lasers grown by metal organic vapor-phase epitaxy

The authors report the fabrication of high-power strained quantum cascade lasers working in continuous mode above 370K. The devices, processed in narrow buried heterostructures, were grown by low-pressure metal organic vapor-phase epitaxy. Continuous wave output power as high as 312mW at 300K was obtained at a wavelength of 5.29μm from a 3.25mm long, 7.5μm wide laser with a high-reflectivity back facet coating. The slope efficiency was in excess of 1.5W∕A and the power conversion efficiency reached almost 5%.

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.

Reduction of the threshold current density of GaAs/AlGaAs quantum cascade lasers by optimized injector doping and growth conditions

Since the first realization of quantum cascade lasers (QCL) in the GaAs material system in 1998, large progress has been made in the device performance of GaAs-based QCLs. However, the relatively high threshold current density of GaAs-based QCLs compared to InP-based QCLs is still the main obstacle for achieving high-temperature continuous wave operation in the GaAs material system. In this work, we investigate the GaAs/Al 0.45Ga 0.55As QCL-design published by Page et al. [Appl. Phys. Lett. 78 (2001) 3529] with 48 active periods embedded in a plasmon enhanced waveguide structure. The optimization of the growth conditions resulted in high-quality quantum cascade structures with operation temperatures up to room temperature. Essential for the fabrication of the high-quality layers was the use of different arsenic fluxes for the waveguide and the active region layers. Furthermore, we varied the doping level in the injector region and we found a strong dependence of this parameter on the threshold current density. The threshold current density is significantly reduced by a factor of 2 due to a decrease of the sheet carrier density by a factor of only 1.6.

High temperature continuous wave operation of Sb-based vertical external cavity surface emitting laser near 2.3 μm

The growth conditions and the operation of a diode-pumped AlGaAsSb/GaInAsSb type-I quantum-well vertical cavity surface emitting laser emitting near 2.3 μm in an external cavity configuration are reported. The epitaxial structure was grown in two steps on a GaSb substrate by molecular beam epitaxy. It is made of a GaSb/AlAsSb Bragg reflector, a GaInAsSb/AlGaAsSb multi quantum-well active region and an AlAsSb heatspreader layer. A TEM 00 low-divergence laser continuous wave mode operation was demonstrated from 277 K up to 350 K. A characteristic temperature T 0 as high as 74 K was measured just below 300 K. Threshold incident pump power as low as 600 W/cm 2 at 277 K and a maximum output power of 8.5 mW at 288 K was observed.

High temperature continuous-wave operation of 1.3- and 1.55-μm VCSELs with InP/Air-Gap DBRs

We demonstrate novel electrically pumped 1.3- and 1.55-/spl mu/m vertical cavity surface emitting lasers (VCSELs) with two InP/air-gap distributed Bragg reflectors (DBRs). The active regions comprise conventional InGaAsP multiple quantum wells. A tunnel junction is placed between the active region and the top DBR to convert electrons into holes, thus minimizing the use of p-type material in the structure to reduce the free-carrier loss and achieve current confinement. The whole structure was grown in a single growth run by low-pressure metal-organic chemical vapor deposition (MOCVD). For both 1.3and 1.55-/spl mu/m emission wavelengths, air-gap DBR VCSELs exhibit room-temperature continuous wavelength (CW) threshold current density as low as 1.1 kA/cm/sup 2/, differential quantum efficiency greater than 30%, and CW operation up to 85/spl deg/C. The single-mode output power was 1.6 mW from a 1.3 /spl mu/m VCSEL with a 6.3-/spl mu/m aperture and 1.1 mW from a 1.55 /spl mu/m VCSEL with a 5.7-/spl mu/m aperture under room temperature CW operation.

High-temperature continuous-wave operation of λ∼8 μm quantum cascade lasers

We report single-mode continuous-wave operation of a λ∼8 μm quantum cascade laser at 140 K. The threshold current density is 4.2 kA/cm2 at 300 K in pulsed mode and 2.5 kA/cm2 at 140 K in continuous wave for 2 mm long index-guided laser cavities of 20 μm width. Wide stripe (W∼100 μm), index-guided lasers from the same wafer in pulsed operation demonstrate an average T0 of 210 K with other wafers demonstrating a T0 as high as 290 K for temperatures from 80 to 300 K. This improvement in high-temperature performance is a direct result of three factors: excellent material quality, a low-loss waveguide design, and a low-leakage index-guided laser geometry.

Characteristics of molecular-beam epitaxially grown pair-groove-substrate GaAs/AlGaAs multiquantum-well lasers

Growth and device characteristics of an index-guided GaAs/AlGaAs multiquantum-well (MQW) laser, called a pair-groove-substrate (PGS) MQW laser, are described in detail. The laser structure is fabricated by using single-step molecular-beam epitaxy on a (001) GaAs substrate with a pair of etched grooves along the 〈11̄0〉 direction. A mesa between a pair of grooves, where the lasing action occurs, becomes narrow during growth, and the narrow mesa offers lateral waveguiding that stabilizes a fundamental transverse mode. The superior crystalline quality of the mesa top, which is examined by a microprobe photoluminescence technique, serves to lower the lasing threshold currents. The lasers with mesa widths below 2 μm show stable transverse mode operation with a low threshold current of 20 mA, as well as a high external differential quantum efficiency of 68%. The low threshold and high characteristic temperature accomplish a high-temperature continuous-wave operation at 153 °C for the lasers mounted on silicon heat sinks.