High-Precision Mid-Infrared Wavelength Measurement via Waveguide-Based MIR-to-NIR Upconversion

Wavelength meters are an important tool to analyse or to stabilize the wavelength of a laser source at very high precision. In the infrared region, wavemeters commonly employ scanning Michelson interferometers attributed to their broadband operational characteristics. The measurement speeds attained by these devices generally fall within the range of several Hertz. Conversely, wavemeters operating in the visible and near-infrared (NIR) domains, which are based on Fizeau interferometers, can achieve measurement speeds of up to 1 kHz. To facilitate the transfer of this measurement speed, mid-infrared light upconversion can be utilized as a range extender for NIR Fizeau wavemeters. In this work, a waveguide-based upconversion module has been developed to convert light from 3.1-3.4 μm to around 1020 nm using difference frequency generation (DFG) with a 780 nm pump laser. Conversion efficiency is important to provide sufficient NIR signal for a low-noise and fast wavelength measurement. Here, waveguide-based systems have the advantages of higher efficiency per Watt pump light compared to bulk converters and simpler and more robust optical setups compared to resonator-based upconverters.