The past decade has seen significant progress in the development of novel mid-infrared (mid-IR) coherent light sources spanning a broad spectral bandwidth, and new spectrometric techniques to make the most of them. Researchers now harness such light sources — based on mode-locked lasers and nonlinear frequency conversion, on frequency comb generators, on supercontinua, and on chip-scale devices such as microresonators — in schemes such as dual-comb spectroscopy, Michelson-based Fourier transform spectroscopy or high-resolution crossed-dispersion spectrometry.
Spectroscopy with these devices is still at an early stage. Yet these techniques hold out the promise of improved molecular sensing for environmental science, analytical chemistry, and biomedicine. Researchers illustrate the field’s progress, and discuss new opportunities and future prospects, especially for on-chip spectrometers that could herald a generation of compact, flexible, and rapid sensing devices.
Mid-IR spectroscopic sensing has a long history, with decades of development, implementation, and continual improvement of powerful instruments. In the laboratory and in industry, mid-IR sensors are routinely used in analytical chemistry and biomedicine. Fourier transform spectrometers — whether ground-based or onboard satellites, aircraft, or atmospheric balloons — have provided broad survey spectra leading to new insights regarding Earth’s atmosphere and climate, and for a host of other meteorological, industrial, and remote-sensing applications.