Potential effects were analyzed after incidence of signal wave firstly. Based on the electromagnetic theory and combined with the nonlinear effect of Stimulated Raman Scattering (SRS) of optical fiber, correlative equations were set up for the Raman amplifying Pump wave of optical fiber, Stokes wave and signal wave and the conditional expression which made system gain form positive feedback was given at the same time. It comes to the conclusion that under the condition that system gain positive feedback is satisfied by optical fiber parameters, the input signal wave is amplified when the SRS gain corresponds to unsaturated gain state; the higher is the SRS gain the more is amplification times; the correlation degree is relatively increased when the SRS gain is relatively low in some region.
In this paper, for the first time we have demonstrated a continuous wave single-pass extracavity frequency doubling by use of MgO doped stoichiometric lithium tantalite (PP-MgO: SLT). The maximum output of the second harmonic green light is 905mW with the pumping power of 7.69W. The second harmonic conversion efficiency is 11.77%. We have theoretically calculated the tolerance of the temperature of SLT SHG which is about 1.5°C. The experimental tolerance of the temperature is consistent with the calculated value.
The refractive index of the periodically poled lithium niobate (PPLN) is about twice as many as the refractive index of the air. When the rotation angle of the periodically poled crystal is bigger, the pump, signal and idler waves can form total internal reflection (TIR) inside the crystal, and the TIR noncollinear quasi-phase-matching (TIR-NQPM) optical parametric oscillator (OPO) can be realized if properly setting the angle of the OPO output coupler synchronously. In this paper, TIR-NQPM OPO based on PPLN pumped with a 1064nm all-solid-state laser is reported for the first time. In our experiment, the angle of rotation for PPLN is 5.57° and 1504~1542 nm of signal wavelength was achieved by tuning the work temperature from 140°C to 250°C. Although adjustment of the cavity is difficult for this method, it broadens the rotation range of angle-tuned QPM OPO. As a result, by one time or more than one time total internal reflections inside the crystal, TIR-NQPM has less limitation of the transverse size of the periodically poled crystal, and the output wavelength range could be increased remarkably.