Abstract
In this paper, we demonstrated efficient mid-infrared generation using a low-power 1064 nm single-frequency (SF) fiber laser based on phase-matched intracavity difference frequency generation (DFG) in a continuous-wave (CW) periodically poled lithium niobate (PPLN)-based optical parametric oscillator (OPO). This is the first time that the frequency down conversion of a low-power SF light source has been achieved using intracavity difference frequency mixing. A high power 1018 nm fiber laser was firstly used for building the parametric oscillation and providing the high power resonant signal wave. To realize an efficient DFG process between the SF pump wave and the intracavity signal wave, the temperature of periodically poled lithium niobate (PPLN) crystal was properly adjusted to satisfy the phase-matching conditions. Finally, the low-power 1064 nm SF pump wave was successfully converted to a 3.7 μm mid-infrared wave with a conversion efficiency of 21.6%. The conversion efficiency, to the best of our knowledge, is the highest for SF lasers in DFG processes. Meanwhile, taking advantage of SF laser pumping, a narrow linewidth of 271 pm (5.9 GHz) in the mid-infrared region was achieved without adding any etalons or devices in the cavity.
Highlights
Mid-infrared sources around 3~5 μm have been widely used in many fields, such as environment monitoring, medical diagnosis and Terahertz (THz) generation [1,2,3,4]
optical parametric oscillator (OPO) require high power pump sources, and it is difficult for single frequency (SF) lasers to achieve high power output directly
Conclusion, we of an laserlaser fromfrom the nearnear-infrared to mid-infrared region based on intracavity for the first time
Summary
Mid-infrared sources around 3~5 μm have been widely used in many fields, such as environment monitoring, medical diagnosis and Terahertz (THz) generation [1,2,3,4]. DFG is a single-pass process with a relatively low efficiency This method requires a high power SF pump source, and a signal source with high enough power to realize the frequency down-conversion of the SF pump source. We realized efficient frequency down-conversion of a low-power fiber source, based on the intracavity DFG process inside the periodically poled lithium niobate (PPLN) OPO. This method adopted a high-power assisted fiber laser to build a parametric oscillation and creatively took full advantage of the high-power intracavity resonant signal beam. Based on the research results we have achieved, in this paper, we demonstrate the highly efficient frequency down-conversion of a low-power SF fiber source using phase-matched intracavity DFG.
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