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.
Highlights
Many high-power, narrow-linewidth fiber lasers operating at 2 μm have been reported, and their output power can reach a level of several hundred watts [17,18,19,20], wavelength stability and high-precision tunability are usually ingnored, which is cruicial for mid-infrared fiber gas lasers (FGLs) [15,16]
We present the use of a high-power, narrow-linewidth 2 μm all-fiber amplifier with a highly stable and precisely tunable wavelength, based on a master oscillator power-amplifier (MOPA) strucMolecules 2021, 26, 5323 ture, which consisted of a narrow-linewidth fiber seed and two stages of Thulium-doped fiber amplifiers (TDFAs)
We present the use of a high-power, narrow-linewidth 2 μm all-fiber amoutput power of plifier the second-stage amplifier was about 24.8 W, with a slope efficiency of with a highly stable and precisely tunable wavelength, based on a MOPA structure, 50.5%
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Narrow-linewidth 2 μm fiber lasers are important pump sources for mid-infrared nonlinear frequency conversion [9,10,11] and gas lasers, as many gas molecules, such as CO2 and HBr have absorption lines in this waveband [12,13,14,15]. Many high-power, narrow-linewidth fiber lasers operating at 2 μm have been reported, and their output power can reach a level of several hundred watts [17,18,19,20], wavelength stability and high-precision tunability are usually ingnored, which is cruicial for mid-infrared FGLs [15,16]. We present the use of a high-power, narrow-linewidth 2 μm all-fiber amoutput power of plifier the second-stage amplifier was about 24.8 W, with a slope efficiency of with a highly stable and precisely tunable wavelength, based on a MOPA structure, 50.5%. The wavelength stability at maximum power was validated by
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