Mid-infrared high-power diode lasers and modules

Abstract

High-power diode lasers in the mid-infrared wavelength range between 1.8µ;m and 2.3µm have emerged new possibilities for applications like processing and accelerated drying of materials, medical surgery, infrared countermeasures or for pumping of solid-state and semiconductor disc lasers. We will present results on MBE grown (AlGaIn)(AsSb) quantum-well diode laser single emitters with emitter widths between 90µm and 200µm. In addition laser bars with 20% or 30% fill factor have been processed. More than 30% maximum wall-plug efficiency in cw operation for single emitters and laser bars has been reached. Even at 2200nm more than 15W have been demonstrated with a 30% fill factor bar. Due to an increasing interest in pulsed operation modes for these mid-infrared lasers, we have investigated single emitters and laser bars at 1940nm for different pulse times and duty cycles. More than 9W have been measured at 30A with 500ns pulse time and 1% duty cycle without COMD for a single emitter. Most applications mentioned before need fiber coupled output power, therefore fiber coupled modules based on single emitters or laser bars have been developed. Single-emitter based modules show 600mW out of a 200µm core fiber with NA=0.22 at different wavelengths between 1870nm and 1940nm. At 2200nm an output power of 450mW ex fiber impressively demonstrates the potential of GaSb based diode lasers well beyond wavelengths of 2µm. Combining several laser bars, 20W out of a 600µm core fiber have been established at 1870nm. Finally for a 7 bar stack at 1870nm we have demonstrated more than 85W at 50A in qcw mode

High-performance single-spatial mode GaSb type-I laser diodes around 2.1 μm

“…We also expect to use this type of device material for next generation single-mode (both longitudinally and spatially) with output powers in excess of several tens of mW's. Presented results are beyond state-of-the-art in terms of output power, WPE and beam quality [4,5].…”

High performance GaSb based digital-grown InGaSb/AlGaAsSb mid-infrared lasers and bars

“…[14] The high performance of the 19-emitter-bar is a good proof that the optimization of the growth technique does not sacrifice the infrared laser performance and also a good proof of emitter uniformity around the whole wafer. [15]…”

High-performance mid-infrared GaSb laser diodes for defence and sensing applications

“…Further improvements in heatsinking and minimizing the thermal resistance are expected to reduce the thermal wavelength shift. Tested devices work CW up to at least 60 deg C (setup limited), maintaining WPE of 19% at 60 deg C. Demonstrated performance can be considered as state-of-the-art [5,6,7], and demonstrates the potential and scalability to large diameter substrates of the GaSb material systems. Transfer to 3-inch diameter substrates is very important for large area device applications such as laser diode linear arrays or 2-D stacks.…”

“…In this case the output power was limited by a thermal roll-over, and higher output powers are expected from longer LD bars with wider emitters. Measured CW WPE of > 28 % is the highest WPE value at 2100 nm reported to date [5,6]. For spectral measurements were carried out using a FTIR spectrometer.…”