Narrow-Linewidth 2 μm All-Fiber Laser Amplifier with a Highly Stable and Precisely Tunable Wavelength for Gas Molecule Absorption in Photonic Crystal Hollow-Core Fibers

Abstract

In recent years, mid-infrared fiber lasers based on gas-filled photonic crystal hollow-core fibers (HCFs) have attracted enormous attention. They provide a potential method for the generation of high-power mid-infrared emissions, particularly beyond 4 μm. However, there are high requirements of the pump for wavelength stability, tunability, laser linewidth, etc., due to the narrow absorption linewidth of gases. Here, we present the use of a narrow-linewidth, high-power fiber laser with a highly stable and precisely tunable wavelength at 2 μm for gas absorption. It was a master oscillator power-amplifier (MOPA) structure, consisting of a narrow-linewidth fiber seed and two stages of Thulium-doped fiber amplifiers (TDFAs). The seed wavelength was very stable and was precisely tuned from 1971.4 to 1971.8 nm by temperature. Both stages of the amplifiers were forward-pumping, and a maximum output power of 24.8 W was obtained, with a slope efficiency of about 50.5%. The measured laser linewidth was much narrower than the gas absorption linewidth and the wavelength stability was validated by HBr gas absorption in HCFs. If the seed is replaced, this MOPA laser can provide a versatile pump source for mid-infrared fiber gas lasers.

High-Power, Narrow-Linewidth, Continuous-Wave, Thulium-Doped Fiber Laser Based on MOPA

“…The comparison for the lasers was mainly at 1900~2000 nm. The maximal output power in the TDFL proposed in this paper was 26 W, which is higher than that in [14,22,28,29]. Furthermore, compared with lasers in [14,22,[28][29][30], the slope efficiency of the proposed TDFL can reach 55.6%.…”

“…The maximal output power in the TDFL proposed in this paper was 26 W, which is higher than that in [14,22,28,29]. Furthermore, compared with lasers in [14,22,[28][29][30], the slope efficiency of the proposed TDFL can reach 55.6%. The comparable and even better results observed for our laser showed the exceptional performance of our proposed TDFL.…”