We demonstrated a tilted fiber Bragg grating (TFBG)-based modulated amplified spontaneous emission (ASE) source, followed by the broadband, continuous-wave (CW) mid-infrared laser generated by intracavity difference-frequency generation (DFG). By flattening the spectrum of the ASE source during its power amplification and injecting another 1018 nm fiber laser in the optical parametric oscillation(OPO) cavity, nonlinear frequency conversion was achieved in the nonlinear crystal. By tuning the polarization period of the crystal, a three-peaked mid-infrared laser with a full width at half maximum (FWHM) of 130 nm and a four-peaked mid-infrared laser with an FWHM of 180 nm was generated.
The research reports broadband, continuous-wave (CW), mid-infrared generation based on an optical parametric oscillator (OPO), pumped by an amplified spontaneous emission (ASE) fiber source. The ASE fiber source has a ytterbium (Yb)-doped fiber master oscillator power amplifier (MOPA) structure. By injecting another fiber laser with high power and a narrow linewidth into the nonlinear crystal, the phase-matching difference frequency generation (DFG) can be realized at a low pumping threshold. It is shown that during the down-conversion of the ASE fiber source, the intracavity DFG can steadily and effectively generate a broadband mid-infrared laser, with a central wavelength of 3713 nm. The bandwidth of the mid-infrared laser is 122 nm. The pump power of 2 W generates a 0.238 W mid-infrared laser with a pump-idler conversion efficiency of 11.6%. It has tremendous application potential in the research of broadband CW mid-infrared lasers.
It was reported that a double-peaked mid-infrared laser was generated based on an intracavity difference frequency generation (DFG). The double-peaked pump source was achieved by suppressing the intensity at the central wavelength of the pump source. The double-peaked mid-infrared generation had a double-peaked spacing of 23–37 nm, and the full width at half-peak (FWHM) of the peaks was up to 30 nm. It was demonstrated that a tilted Bragg fiber grating (TFBG) with a specific transmission spectral depth and bandwidth can generate a double-peaked mid-infrared laser with controllable double-peaked spacing. It was the first generation of a double-peaked mid-infrared laser based on a near-infrared pumping spectral modulation. Furthermore, the double-peaked mid-infrared generation was tunable, and the FWHMs of the peaks were controllable by an intracavity DFG. It had a high potential for the monitoring and absorption of gas molecules by differential absorption lidar (DIAL).
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