Investigation On The Gain Properties Of Optical Parametric Amplification Under The Broadband Pumping

With the development of a large number of good quality nonlinear crystals and the electric field domain poling technique, nonlinear optical parametric amplification and oscillation become the main-stream technique in achieving broadband wavelength tunable laser output, which is impossible for common solid-state lasers. More and more researchers have been focusing on the study of nonlinear optical parametric conversion technology. With the mature high-power solid-state laser as the pump source, the mid-infrared and far-infrared band tunable laser output can be achieved, through nonlinear optical parametric amplification and oscillation. These lasers have important roles in optoelectronic counter measurement, infrared jamming, laser radar, environmental test, medical treatment and other fields. This thesis focuses on the study of broadband pumped nonlinear optical parametric amplification and oscillation. The characteristics of spectral bandwidth and gain are analyzed. The general mathematical expression to describe spectral bandwidth is given out. Optical parametric oscillation pumped with a broadband pulsed fiber laser is experimentally demonstrated. The 5mol% doping PPMgLN is used as nonlinear crystal. The parametric output wavelength tunable from 1410 nm to 1620 nm is obtained. Spectral bandwidth and power characteristics are investigated.This thesis includes the following three parts:(1) Investigation on the tunability and the tolerance of optical parametric amplification based on monochromatic pump; (2) Study of spectral bandwidth and the gain properties based on the broadband pumped optical parametric amplification; (3) Experimental investigation on the broadband pumped optical parametric oscillation.Tunability and tolerance of optical parametric amplification is of great significance in achieving efficient nonlinear optical frequency conversion. Based on the monochromatic pump optical parametric amplification, the tunability and tolerance characteristics are systematically studied, through Taylor expansion of nonlinear phase mismatch function in three-wave coupling process. It is first found that there exists a compression point in parametric output wavelength toward pump bandwidth. Parametric output wavelength possesses the largest pump acceptant bandwidth near the compression point. Parametric output wavelength is stable even with drifting pump wavelength near the compression.Broadband pump optical parametric amplification and oscillation have important applications in the cascaded optical parametric oscillation and the broadband optical parametric amplification. However, related theoretical studies have rarely been reported. In this thesis, the spectral bandwidth and the gain characteristics are investigated for the broadband pumped optical parametric amplification. We find that the amplification factor of the pump bandwidth varies with the parametric wavelength, the noncollinear angle and temperature. Parametric wave possesses the narrowest spectral and the largest gain near the compression point.Finally, optical parametric oscillator pumped with a pulsed SPI fiber laser is experimentally demonstrated. The laser is 6.2 nm in bandwidth with a pulse duration between 10 and 20 ns. Parametric wavelength ranging from 1410 nm to 1620 nm are achieved. The spectral bandwidth and the power properties are investigated. Through experimental study, we find the highest power output is near 1530 nm. When the parametric output wavelength deviated from 1530 nm,the output power decreases gradually. The conclusion is in good accordance with the theoretical analysis and numerical simulations.