In this paper, a novel dual-wavelength (DW) mid-infrared optical parametric oscillator (OPO) pumped by a DW Raman fiber oscillator is demonstrated. The DW Raman fiber oscillator fixed at 1070 nm and 1120 nm was obtained using a homemade linear-polarized 1070 nm fiber laser, a wavelength division multiplexer(WDM), a pair of fiber Bragg gratings (FBGs) and a 35-meter polarization-maintaining (PM) passive fiber. At first, only the 1070 nm laser performed the oscillation process and generated signal laser fixed at 1590 nm and idler laser fixed at 3270 nm. As the pump power continued to grow, more and more power was transferred to 1120 nm laser. When the 1120 nm laser was over 11.04 W, it also built its own optical parametric process independently and generated 1614nm signal laser and 3662 nm idler laser, while the oscillation corresponded to 1070 nm remained the same. The output total DW mid-infrared power reached 4.96 W with a maximum pump-idler conversion efficiency of 9.9%. This scheme was not only easy to complement, but also utilize the backward Raman laser to increase the efficiency. The experiment result shows great potential in spectral regulation and cascaded Raman fiber laser can also be used as the pump source to achieve multi-wavelength midinfrared output.
We report efficient frequency downconversion of a continuous-wave low-power Raman laser using intracavity difference frequency mixing in a periodically poled lithium niobate (PPLN)-adopted optical parametric oscillator (OPO). The Raman laser was obtained using a 1060-nm fiber laser and 137-m passive fiber. Its central wavelength was fixed at 1111 nm with the power ranging from 320 mW to 5.984 W. The 1060- and 1111-nm pump beams were incident into the OPO at the same time. The high-power 1060-nm pump beam built parametric oscillation first, and the difference frequency generation (DFG) occurred between the low-power Raman laser and intracavity signal laser. The PPLN temperature was properly controlled at 45°C to ensure both the OPO and DFG processes synchronously satisfy phase matching conditions. Benefiting from intracavity high signal power, the Raman laser was successfully converted to the 3560-nm midinfrared radiation under every investigated pump power level. The maximum 3560-nm idler power reached 1.026 W, indicating a 17.4% pump-to-idler slope efficiency and about 15% optical-to-optical conversion efficiency. The comparative experiments also verified that the phase matching conditions were satisfied maximally at 45°C.
In this paper, a dual-wavelength(DW) mid-infrared optical parametric oscillator(OPO) pumped by a DW fiber laser based on the stimulated Raman scattering(SRS) effect, is demonstrated. When the pump power satisfied the threshold condition, obvious SRS effect was observed and a DW fiber laser with center wavelengths at 1060 nm and 1113 nm was obtained. The DW fiber laser was injected into a single-period crystal, and the whole process went through four stages. In the first three stages, 1060 nm pump laser achieved parametric oscillation and generated 1602 nm signal laser and 3138 nm idler laser and the conversion efficiency was seriously affected by SRS effect. In the fourth stage, two independent parametric processes were realized, which generated two mid-infrared output at 3131nm and 3580nm with powers of 2.46W and 40mW, respectively. The efficiency characteristics in the four stages were also discussed separately.
We demonstrate an all-fiber gain-switched thulium-doped fiber laser (TDFL) producing nanosecond pulses with variable wavelength in the 2 μm waveband. The laser features tunable operation in an ultra-wide spectral region of 1765 – 2055 nm (24 THz). The nearly 300 nm tunability doubles the record tuning range of existing gain-switched fiber lasers, and to the best of our knowledge, presents the broadest tuning range that has been reported for a monolithic pulsed rare earth doped fiber laser to date. The TDFL can operate at a repetition rate of 5 – 100 kHz with a pulse width as short as ~200 ns. A modest compromise in the tuning range allows pulse width reduction to sub-100 ns.