Observation of acetylene molecular absorption line with tunable, single-frequency, and mode-hop-free erbium-doped fiber ring laser

We succeeded in observing one of the absorption lines of acetylene [P(16)] using an erbium-doped fiber-ring laser, which is the first such observation using a fiber-ring laser. The observed linewidth of the P(16) linear absorption was approximately 450 MHz. Mode competition and mode hopping were suppressed by using an ultra narrow-band fiber Bragg grating and a Fabry-Perot filter in the ring laser, respectively. Wavelength fine-tuning was carried out by. changing the cavity length of the fiber-ring laser; the fine-tuning range was about 850 MHz (0.01 nm). Furthermore,wavelength tuning was achieved by controlling the temperature of the fiber Bragg grating, and the coarse tuning range was about 0.2 nm.