CW Optical Output Research Articles

Strain induced power enhancement of far-UVC LEDs on high temperature annealed AlN templates

High temperature annealed AlN/sapphire templates exhibit a reduced in-plane lattice constant compared to conventional non-annealed AlN/sapphire grown by metalorganic vapor phase epitaxy (MOVPE). This leads to additional lattice mismatch between the template and the AlGaN-based ultraviolet-C light emitting diode (UVC LED) heterostructure grown on these templates. This mismatch introduces additional compressive strain in AlGaN quantum wells resulting in enhanced transverse electric polarization of the quantum well emission at wavelengths below 235 nm compared to layer structures deposited on conventional MOVPE-grown AlN templates, which exhibit mainly transverse magnetic polarized emission. In addition, high temperature annealed AlN/sapphire templates also feature reduced defect densities leading to reduced non-radiative recombination. Based on these two factors, i.e., better outcoupling efficiency of the transverse electric polarized light and an enhanced internal quantum efficiency, the performance characteristic of far-UVC LEDs emitting at 231 nm was further improved with a cw optical output power of 3.5 mW at 150 mA.

Improving Reliability of cw Bar Laser Diodes by Novel Mounting

High power bar laser diodes, with CW optical power output were studied experimentally. A novel mounting was designed to bring the coolant as close as possible to the laser bar in order to improve the bar laser diode characteristics. Thermal properties can influence significantly device characteristics, affecting wavelength, maximum output power, threshold current, slope efficiency and operating lifetime. Stable emission (803 nm) of the bar laser diodes was maintained during the investigation since it is very important for different kinds of applications. A high external quantum efficiency of (1.66) and a characteristic temperature of (106 oC) were obtained in our experimental setup. A reliable and high performance IR bar laser diode source was achieved experimentally.

High-temperature, high-power, continuous-wave operation of buried heterostructure quantum-cascade lasers

We report cw operation of buried heterostructure quantum-cascade lasers (λ=6 μm) using a thick electroplated Au top contact layer and epilayer-up bonding on a copper heat sink up to a temperature of 333 K (60 °C). The high cw optical output powers of 446 mW at 293 K, 372 mW at 298 K, and 30 mW at 333 K are achieved with threshold current densities of 2.19, 2.35, and 4.29 kA/cm2 respectively, for a high-reflectivity-coated, 9-μm-wide and 3-mm-long laser.

High-power continuous-wave operation of a 6 μm quantum-cascade laser at room temperature

We report continuous-wave (cw) operation of quantum-cascade lasers (λ=6 μm) using a thick electroplated Au top contact layer and epilayer-up bonding on a copper heat sink up to a temperature of 308 K (35 °C). The high cw optical output powers of 132 mW at 293 K and 21 mW at 308 K are achieved with threshold current densities of 2.29 and 2.91 kA/cm2, respectively, for a high-reflectivity-coated 15 μm wide and 2 mm long laser.

High power InAsSb/InAsSbP double heterostructure laser for continuous wave operation at 3.6 μm

High continuous wave (cw) optical output power of 10 mW has been achieved from an InAsSb diode laser at 82 K in the 3.6 μm spectral region. The threshold current has been as low as 37 mA at 82 K with a characteristic temperature of 23 K. It could be shown that in multimode operation of the InAsSb-laser the cw optical output power for a single lasing mode is limited to about 2 mW.

ACTIVE MODE-LOCKING OF A DIODE-PUMPED Ce, Nd: YAG

We have developped a mode-locked Ce, Nd:YAG laser end-pumped by a 500 mW laser diode. With a short cavity configuration the cw optical output power was 155 mW, which corresponds to an optical efficiency of 30.9 % and an electrical efficiency of 9.5 %. A cavity length extended to 1.4 m allows mode -locked operation at 106 MHz and pulses widthes of 150 ps have been obtained with an average power of 23 mW.

High average power edge emitting laser diode arrays on silicon microchannel coolers

We have demonstrated high average power output devices in both one-dimensional (1-D) and two-dimensional (2-D) arrays of laser diodes using efficient edge emitting cleaved bars and silicon microchannel coolers. These packages are based on the rack and stack architecture. For the 1-D array a cw optical power output of 22.2 W was obtained with 20% electrical to optical conversion efficiency. For the 2-D array an average optical power density of greater than 100 W/cm2 was obtained at an efficiency of 25%.

Continuous wave high-power, high-temperature semiconductor laser phase-locked arrays

Continuous wave GaAlAs semiconductor laser arrays are reported to emit 585-mW/facet cw optical output power at room temperature. The lasers operate over 100 °C with output powers in excess of 200 mW/facet cw. Laser thresholds are as low as 130 mA, differential quantum efficiencies exceed 60% for some devices, and very high total power conversion efficiencies of over 20% are observed.

CW Optical Power from (Al·Ga)As Double Heterostructure Lasers

CW optical output power was investigated in (Al·Ga)As double heterostructure lasers. An analysis on CW optical power is presented, and parameters related to device characteristics and heat-sinking are analyzed in order to obtain laser operation with high CW optical power. 20–30 mW CW optical power was obtained routinely from each mirror of lasers with a 15 µm wide stripe and a 250 µm long cavity at a typical operating current of 200 mA. Lasers with a Si heat sink can deliver comparably high CW optical power under proper choice of design parameters. Several lasers delivered 85 mW in CW with a Si heat sink from each mirror at 310 mA, before the catastrophic optical mirror damage occurred. Conditions for long life operation are also discussed.

The cross-beam electric-discharge convection laser

An experimental investigation of a 60-cm-wide × 2.5-cm-high N <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> -CO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> cross-beam electric-discharge convection laser (EDCL) is described. In the cross-beam EDCL, the discharge is maintained along the flow in a rectangular cross-section channel and optical power is extracted transverse to the discharge and flow. High mass flow rates are employed to achieve high volumetric power densities. Experiments relating to the achievement of uniform and stable discharges at high-power levels in the rectangular laser channel, and measurements of the small-signal gain characteristics, amplifier performance, and optical quality are described. Using an 11-pass optical scheme, a CW optical output power of 2 kW has been extracted from the amplifier at an electrical efficiency of 9.6 percent.