Using a DS-DBR laser for widely tunable near-infrared cavity ring-down spectroscopy

Studies into the suitability of a novel, widely tunable telecom L-band (1,563-1,613 nm) digital supermode distributed Bragg reflector (DS-DBR) laser for cavity ring-down spectroscopy (CRDS) are presented. The spectrometer comprised of a 36.6∈cm long linear cavity with ring-down times varying between 19-26 μs across the 50 nm DS-DBR wavelength range due to changes in the cavity mirror reflectivities with wavelength. The potential of such a broadband, high-resolution CRD spectrometer was illustrated by investigating several transitions of CO2 in air, a 5 % calibrated mixture and breath samples. Allan variance measurements at a single wavelength indicated an optimal minimum detectable absorption coefficient (α min) of 3 × 10-10 cm-1 over 20 s. © 2013 Springer-Verlag Berlin Heidelberg