2-μm-Band Monolithic Tunable Laser With Over-100-nm Tuning Range for CO2 TDLAS

Tunable diode laser absorption spectroscopy (TDLAS) using compact, low-power consumption and cost-effective semiconductor lasers is suitable for ubiquitous gas sensing. TDLAS in a 2- $\mu $ m wavelength band is ideal for sensing carbon dioxide (CO2), a typical greenhouse gas, in terms of its low absorption interference with hydrogen oxide (H2O), recognized as a common background in gas sensing. In this letter, we describe a 2- $\mu $ m-band tunable laser in which an optical gain and a tunable filter are monolithically integrated on the same semiconductor chip, which is competitive in terms of the optical assembly cost. The tuning range of the laser is over 100 nm, which is the widest among 2- $\mu $ m-band monolithic tunable lasers. The wide tuning range contributes to improving the number of detectable absorption lines per laser system, resulting in higher-flexibility of CO2 TDLAS. Using the laser, we successfully confirmed practical CO2 sensing.