Frequency Down-Conversion of Dual-Wavelength Raman Fiber Laser in PPLN-Based Optical Parametric Oscillator

Abstract

We report on frequency down-conversion of dual-wavelength (DW) Raman fiber laser in a periodically poled lithium niobate-based optical parametric oscillator. The DW pump source was fixed at 1060 and 1111 nm that was obtained based on stimulated Raman scattering effect by combining a home-made linearly polarized 1060-nm fiber laser and 137m-long polarization-maintaining passive fiber. The total pump power went through three stages, in the latter two of which the 1111-nm wave appeared. In the entire experiment, the 1060-nm pump beam achieved parametric oscillation and generated 1626-nm signal beam and 3056-nm idler beam. The 1111-nm pump beam generated 3503-nm idler beam based on difference frequency generation (DFG) between itself and 1626-nm signal beam in the second stage. With power enhancement, it built independent parametric oscillation in the third stage and generated 1621-nm signal beam as well as 3530-nm idler beam. The DW idler power ranged from 3.94 to 7.78 W in the latter two stages. The power and efficiency characteristics in frequency conversion processes of 1060-and 1111-nm pump beams were also analyzed separately.

A High Efficient Dual-Wavelength Mid-Infrared Optical Parametric Oscillator Pumped by the Raman Fiber Oscillator

“…Besides, the Raman threshold was 12.7 W, which was also much lower than 51.5 W in the Ref. [16], enabling the Raman laser to build independent parametric oscillation in the following process more easily.…”

“…The conversion efficiency first increased rapidly as the 1120 nm pump power increased and finally remained around 13%, which demonstrated good agreement with simulation curve. The maximum pump-to-idler conversion efficiency of Raman laser was calculated to be 13.3%, which was greatly improved and was as 3 times as before [16]. The simulation results show that the conversion efficiency curve start to decline after reaching the maximum, which means that over-continued increase in power, however, will led to reduced efficiency due to the back conversion.…”

“…It can be seen that just like traditional Raman fiber oscillators, the power was transferred to Raman laser rapidly, and consequently made the Raman conversion efficiency grew continuously and reached maximum at 72.1%, which was almost as 3 times high as that in the Ref. [16]. The slow depletion of residual 1070 nm laser limited the further improvement of Raman efficiency, however enabling the 1070 nm laser to participate in the following parametric process and generate dual-wavelength mid-infrared output.…”

“…As a common application of frequency conversion, the stimulated Raman scattering (SRS) effect has been studied thoroughly [13]- [15]. In 2018, our research group built a 1060&1111 nm dual-wavelength Raman fiber laser which was adopted as the OPO pump source and obtained 3054&3530 nm dual-wavelength mid-infrared radiation [16]. However, the fiber pump source did not involve a Raman resonant cavity, resulting in low Raman conversion efficiency at around 26.7%.…”

Highly Efficient Mid-Infrared Generation from Low-Power Single-Frequency Fiber Laser Using Phase-Matched Intracavity Difference Frequency Mixing

“…Our research group has made some achievements in utilizing a high-power intracavity signal beam to achieve mid-infrared output. In 2018, our group realized a tunable dual-wavelength mid-infrared output by using the 1060 and 1070-1090 nm tunable fiber laser as the pump source [13]. By utilizing intracavity DFG, the 1070-1090 nm tunable fiber laser, whose power was insufficient to build the OPO process, was successfully converted to the mid-infrared region.…”