Development of a compact gas sensor system using an ECDL by laser Raman spectroscopy

Abstract

Laser Emission of a blue ECDL at a single transverse mode (TEM00) was confirmed and Raman spectra of O2 and N2 in the atmosphere were acquired using the intra-cavity beam of the ECDL. The center wavelength of the diode laser is 416 nm in the blue region of the visible spectrum. A Fabry-Perot resonator composed of two high reflectivity mirrors was used as an external cavity and a fraction of the intra-cavity beam was feedbacked to the anti-reflection coated facet of the diode laser. The optical feedback makes it possible that the diode laser oscillates stably at a specific frequency in the gain band of the laser diode chip. This configuration includes only four optics and has potential to be utilized as a compact Raman gas sensor that can be mounted on drones or the other machines. The detection limits in 1 second integration time were estimated to be lower than 100 ppm in the case of N2 gas and 200 ppm in O2, respectively.