Cavity Enhanced Absorption Spectroscopy Based on a Tunable DFB Diode Laser

The Cavity enhanced absorption spectroscopy based on a tunable DFB diode laser (TDL-CEAS) was described. A brief introduction of cavity enhanced absorption spectroscopy development and experimental scheme was given, the effective absorption path of the medium in the optical cavity was interpreted from the way of FabryPerot cavity. It is pointed out that the main reason why CEAS has high detection sensitivity is that the medium in the cavity can get a long absorption path. A tunable DFB diode laser which center wavelength is 1.573 μm was used as the light source, and an optical cavity which consists of two high reflectivity mirrors (near 1.573 μm, R about 0.994) separated at a distance of 34 cm was used as the absorption cell. Laser radiation was coupled into the optical cavity via accidental coincidences of laser frequency with the cavity mode when scanning the cavity and the laser. An absorption spectrum of carbon dioxide near 1.573 μm was obtained and a detection sensitivity of about 1.66×10-5 cm-1 was achieved. It is experimentally demonstrated that the CEAS is a highly sensitive and high resolution spectrum technology， and it has the advantage of simple experimental setup and easy operation.