Narrowband ns and ps laser sources for the wide infrared spectral range based on nonlinear light conversion

Widely tunable narrowband mid-infrared coherent sources, realized using optical parametric oscillators, play an essential role in spectroscopic investigations. A part of mid-infrared spectral region is a "fingerprint range" of solid-state materials, therefore, narrow linewidth is a particularly important feature. The most suitable linewidth of radiation to satisfy the required resolution for spectroscopy of solids is 2‒6 cm⁻¹. The biggest challenge for the developer of the laser source is meeting customers' needs and providing numerous parameters simultaneously from a single device: broad spectral range, high spectral resolution, fast wavelength tuning, high repetition rate, stable beam direction, nearly diffraction-limited divergence, etc. All this should be provided throughout the entire operational spectral range. These features are relevant for many applications, especially for Scanning Near-field Optical Microscopy (SNOM). This presentation will describe the architecture and applications of EKSPLA's broadly tunable commercial ns and ps laser sources, from 2 to 18 μm based on OP-GaAs fan-type gratings and other mid-infrared OPO nonlinear crystals. The advantages and limitations of the crystals in different narrowband OPO setups will be presented.