In this paper, we show results of further brightness improvement and power-scaling enabled by both the rise in chip brightness/power and the increase in number of chips coupled into a given numerical aperture. We report a new chip technology using x-REM design providing a record ~340 W output from a 2×12 nLIGHT <i>element</i>® in 105 μm diameter fiber. These diodes will allow next generation of fiber-coupled product capable of >250W output power from 105 μm/0.15 NA beam at 915 nm. There is also an increasing demand for low SWaP fiber-coupled diodes for enabling compact high energy laser systems for defense applications. We have demonstrated 600 watts and 60% efficiency at 15C in 220 μm/0.22 NA fiber resulting in specific mass and volume of 0.44 kg/kW and of 0.5 cm<sup>3</sup>/W respectively.
Multi-kilowatt, continuous-wave fiber lasers continue to drive the need for higher power, higher brightness, and more efficient diode laser pump modules. It is well documented that increases in pump module power either enable higher power CW fiber lasers or minimize complexity of the multi-stage fiber combiners for a given power. Additionally, increasing pump module brightness positively impacts the SRS threshold of a given multi-kilowatt CW fiber lasers architecture. We report on the continued progress by nLIGHT to develop and deliver the highest brightness diode-laser pumps using single-emitter technology at 976 nm for Ytterbium fiber laser pumping. Building upon our prior developments that have enabled higher emitter counts in the element® packages, nLIGHT is releasing two new 976 nm module configurations: a 2×7 module with 155 W into 105 μm – 0.15 beam NA, and a 375 W 2×12 into 200 μm – 0.16 beam NA. Additionally, we have demonstrated high efficiency designs utilizing a new chip on submount (COS) architecture: with a 430 W 2×12 into 200 μm – 0.16 beam NA and 57% electro-optical efficiency, and an alternative 2×15 design resulting in 600 W at 57 % electro-optical efficiency at 23 A when coupled into 200 μm – 0.18 beam NA.
Terahertz detection using excitations of plasmon modes offers a high-speed, high resolution, and frequency-selective
alternative to existing technology. Plasmons in high mobility quantum well two-dimensional electron gas (2DEG)
systems can couple to radiation when either the channel carrier density, or the incident radiation, is spatially modulated
with appropriate periodicity. Grating-gated terahertz detectors having a voltage tunable frequency response have been
developed based on this principle. A continuous wave THz photomixer was used to characterize the resonant absorption
in such devices. At the fundamental 2DEG plasmon frequency, defined by the grating and the quantum well carrier
density, a 20% change in transmission was observed. As the resonance is tuned from the 'natural' plasmon frequency
through application of a gate bias, it shifts as expected, but the transmission change drops to only a few percent.