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Stable dual-wavelength operation of InGaAs diode lasers coupled with volume Bragg gratings has been demonstrated for the continuous wave and gain-switching regimes. Spectral narrowing down to 0.33nm has been realized with maximum output power of up to 1.85W from a broad area stripe laser diode in a single-grating external cavity configuration. Spectral separation from 0.5 (0.16THz)to6.5nm (2.05THz) has been obtained and an output power of up to 1.75W was achieved in dual-wavelength operation.

Atmospheric methane concentration levels were detected using a custom built laser dispersion spectrometer in a long open-path beam configuration. The instrument is driven by a chirped distributed feedback mid-infrared quantum cascade laser centered at ~1283.46 cm^-1 and covers intense rotational-vibrational transitions from the fundamental ν₄ band of methane. A full forward model simulating molecular absorption and dispersion profiles, as well as instrumental noise, is demonstrated. The instrument's analytical model is validated and used for quantitative instrumental optimization. The temporal evolution of atmospheric methane mixing ratios is retrieved using a fitting algorithm based on the model. Full error propagation analysis on precision gives a normalized sensitivity of ~3 ppm.m.Hz^-0.5 for atmospheric methane.

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We report terahertz (THz) generation from InAs/GaAs quantum-dot based photoconductive antennae with femtosecond optical excitation at 800 nm, with an estimated infrared-to-THz conversion efficiency of ∼0.9×10−5. The quantum dots act as recombination centers for carriers generated in the GaAs layers within the structure. Photoreflective pump-probe measurements reveal a decrease in the carrier lifetime when a lateral voltage is applied. These antennae displayed resilience to Joule heating when operated at a field strength of 46 MV/m. The breakdown field of the devices was 48 MV/m, which is comparable to the breakdown field of bulk GaAs.