An optical frequency comb operating in the mid-infrared region for wide-range and high-precision optical sensor

This paper presents a development of a mid-infrared laser expected to be used as sensor light source for precision engineering measurement. A ring oscillator based on nonlinear polarization rotation with erbium-doped-fluoride fiber was developed. Laser oscillation at the wavelength of $2.8\, \mu \mathrm {m}$ was obtained with pumping the fluoride fiber by a diode laser at the wavelength of 976 nm. A spectrometer was also developed for real-time measurement of spectra of the laser oscillation. As a result of observing a spectrum, only continuous wave oscillation was gained.