Double-channel Ridge Waveguide Research Articles

InP-Based Surface-Emitting Distributed Feedback Lasers Operating at 2004 nm

We demonstrate InP-based buried grating coupled surface-emitting distributed feedback (DFB) lasers designed to operate at a wavelength of 2004 nm. The laser structure consists of three InGaAsSb/InGaAs QWs, with a 5 $\mu \text{m}$ wide double-channel ridge waveguide. A second-order semiconductor/semiconductor grating is used for in-plane feedback and vertical out-coupling. The single longitudinal mode emission wavelength of the fabricated laser can be adjusted from 2002.7 to 2006 nm without any mode hopping. High side-mode suppression ratio (SMSR) of at least 35 dB is achieved under all injection currents and temperature conditions. The edge output power reaches 19 mW, measured in continuous-wave (CW) mode at 10 °C. Simultaneously, the output power of surface emission reaches 8 mW.

Thermal effects in quantum cascade lasers at λ∼4.6 μm under pulsed and continuous-wave modes

The thermal effects in InGaAs/InAlAs quantum cascade lasers (QCLs) emitting at λ∼4.6 μm under pulsed and continuous-wave (CW) modes using a three-dimensional (3D) heat dissipation model were investigated. Based on the experimentally measured results, the thermal characteristics were theoretically analyzed for various device and heatsinking structures. Also, the heat accumulation effects and dissipation processes were studied in detail under pulsed operation. High cooling efficiencies were achieved by a relatively fast heat diffusion rate from the active core region for the epilayer-down bonded single ridge waveguide buried heterostructure (BH) with a thick electroplated Au around the laser ridge. A further improvement was made by the use of InP embedding layer. In CW mode, the thermal conductance (G th) value of 445 W/(K cm2) at 298 K was obtained for the epilayer-down bonded double-channel ridge waveguide QCL with AlN submount, which indicates a reasonable consistency with the available experimental data. By optimizing the device and heatsinking structures, the G th was improved to a high value of 673 W/(K cm2) at 298 K for the epilayer-down bonded single ridge waveguide BH QCL with InP embedding layer on diamond submount in CW mode.

Thermal analysis of InP-based quantum cascade lasers for efficient heat dissipation

We have theoretically investigated the thermal characteristics of double-channel ridge–waveguide InGaAs/InAlAs/InP quantum cascade lasers (QCLs) using a two-dimensional heat dissipation model. The temperature distribution, heat flow, and thermal conductance (Gth) of QCLs were obtained through the thermal simulation. A thick electroplated Au around the laser ridges helps to improve the heat dissipation from devices, being good enough to substitute the buried heterostructure (BH) by InP regrowth for epilayer-up bonded lasers. The effects of the device geometry (i.e., ridge width and cavity length) on the Gth of QCLs were investigated. With 5 μm thick electroplated Au, the Gth is increased with the decrease of ridge width, indicating an improvement from Gth=177 W/K⋅cm2 at W=40 μm to Gth=301 W/K⋅cm2 at W=9 μm for 2 mm long lasers. For the 9 μm×2 mm epilayer-down bonded laser with 5 μm thick electroplated Au, the use of InP contact layer leads to a further improvement of 13% in Gth, and it was totally raised by 45% corresponding to 436 W/K⋅cm2 compared to the epilayer-up bonded laser with InGaAs contact layer. It is found that the epilayer-down bonded 9 μm wide BH laser with InP contact layer leads to the highest Gth=449 W/K⋅cm2. The theoretical results were also compared with available obtained experimentally data.

Room temperature continuous wave operation of quantum cascade lasers with 12.5% wall plug efficiency

An InP based quantum cascade laser heterostructure emitting at 4.6μm was grown with gas-source molecular beam epitaxy. The wafer was processed into a conventional double-channel ridge waveguide geometry with ridge widths of 19.7 and 10.6μm without semi-insulating InP regrowth. An uncoated, narrow ridge device with a 4.8mm cavity length was epilayer down bonded to a diamond submount and exhibits 2.5W maximum output power with a wall plug efficiency of 12.5% at room temperature in continuous wave operation.

Optimization of 660-nm-Band AlGaInP Laser Diodes by Using Deep-Level Transient Spectroscopy Analyses

We report high power and high temperature operation of 660-nm-band AlGaInP laser diodes. The double-channel ridge waveguide structure was used, and the growth conditions for each layer of the AlGaInP laser were optimized to have the lowest defect density by using deep-level transient spectroscopy (DLTS) analyses. The optimized AlGaInP lasers showed better performance than those fabricated without optimization. One of the optimized AlGaInP lasers showed a very stable fundamental transverse mode even at 200 mW and 70 ◦C, a typical threshold current of 64 mA at 660 nm, a slope efficiency of 1.0 W/A, and a characteristic temperature of 212 K. The beam divergences perpendicular and parallel to the junction plane were 15.3◦ and 8.6◦, respectively, at 80 mW CW, which is small enough for a DVD-R/RW system.

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 μm) 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 xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , respectively, for a high-reflectivity-coated 12-μm-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 μm. A clear trend of improved performance is observed as the ridge narrows.

Sputtered AIN films for semiconductor lasers

The deposition rates and properties of AIN films produced by r.f. sputter deposition are dependent on the discharge mixture pressure, discharge voltage and depositing time. The breakdown electric field of the AIN films can range from 3.6×10 6 to 9.1×10 6 V cm −. These films have been successfully used as a new dielectric facet reflector and protector for 850 nm GaAs/GaAlAs double-heterostructure lasers. A 1300 nm InGaAsP/InP heterostructure laser with a double-channel ridge waveguide structure was successfully made by the deposition of an AIN film as the passivating layer. The data for AIN, Al 2O 3, SiO 2, Si 3N 4, GaAs and InP were compared, and AIN is the best of these in the field of semiconductor optoelectronic devices on a substrate of GaAs or InP.