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We demonstrate compressive spectroscopy at 3.3 µm by projecting a sparse set of spectra shaped by a digital micromirror device. Acquisition at 280 Hz is achieved. Reconstructed spectroscopy shows good agreement with ground truth measurements.

Orientation-patterned gallium phosphide [1] (OPGaP) is a wide-bandgap material enabling two-photonabsorption-free pumping using 1040-nm Yb-lasers, and such OPGaP optical parametric oscillators (OPOs) have been applied in Fourier-transform [2] and dual-comb [3] spectroscopies across the 5–12-μm molecular fingerprint region. Hetero-epitaxial growth of GaP on orientation-patterned gallium arsenide (OPGaAs) templates has been developed [4] , to mitigate issues with GaP substrates, but no nonlinear frequency conversion has yet been demonstrated. Here we report the first efficient frequency conversion in OPGaP-on-OPGaAs. OPGaP layers up to 1.2-mm thick were grown by hydride vapor-phase epitaxy (HVPE) on a 3-inch MBE-grown OPGaAs template. Several multi-grating and fan-out crystals of lengths 1.1 mm and 2.9 mm were diced from the wafer and polished into plane-parallel chips, and a broadband anti-reflection coating was applied to both faces.

We present an eye-safe active FTIR spectroscopy system based on a broadband ultrafast optical parametric oscillator (OPO) operating in the 3.1–3.5-μm wavelength range (where common hydrocarbons display absorption peaks) and capable of acquiring gas absorption spectra from a simple target. We demonstrate that simultaneous quantitative measurement of atmospheric background levels of water and methane is readily achieved by this system, even in the presence of strong absorption from a control cell of 1.5% ethane.

Atmospheric gas sensing using unmanned aerial vehicles (UAVs) is growing in importance because of the wide range of applications this technology can flexibly address, such as climate monitoring [1], pollution detection [2], volcanology [3], and hazardous scene assessment [4]. The benefits over conventional approaches are striking: drones can be deployed quickly at low cost and without the need for dedicated runways, can operate in contaminated or hazardous environments, and can perform systematic high-resolution surveys in three-dimensional space with a high repeatability. Here we report the first intrinsically multi-species gas sensing using a UAV-integrated Fourier-transform spectrometer with long-wavelength infrared spectral coverage extending deep into the molecular fingerprint region.

The rapidly developing semiconductor industry demands constant innovations in optoelectronic imaging of semiconductor integrated circuits to keep up with continuing device scaling. It was recently shown that two-photon laser-assisted device alteration (2pLADA) can deliver precision fault isolation. Here we describe an investigation into the influence of the incident light polarization on the 2pLADA spatial resolution. Linear polarization provides a highly confined but elliptical focal spot, while circular polarization diminishes the lateral resolution but benefits from a symmetrical focal spot. Radially polarized light potentially provides the highest lateral imaging resolution in all directions at the expense of the longitudinal resolution. By comparing 2pLADA results obtained using linear, circular and radial polarizations we show that certain polarizations have advantages in particular applications. Therefore a polarization optimized 2pLADA tool can achieve a sufficiently high performance to isolate faults of transistors separated by as little as 100 nm and maybe smaller.