Liang B L, Wang Z, Cartwright C M, Gillespie W A, Ding M S, Zhang H
Appl Opt. 2001 Jul 10;40(20):3359-64. doi: 10.1364/ao.40.003359.
We have improved the two-wave coupling amplification and the signal-to-noise ratio of an amplified signal with photorefractive cerium-doped potassium sodium strontium barium niobate (Ce:KNSBN) by employing optimum polarization orientation of the pump beam while the signal beam retains extraordinary polarization. The optimum polarization angle of the pump beam was found experimentally to be 30 degrees with respect to the extraordinary polarization direction in a symmetrically incident system. Nearly 1.9-times enhancement of the gain and nearly 3-times enhancement of the signal-to-noise ratio were achieved at a signal-to-pump beam intensity ratio of 1:40. At a beam intensity ratio of 1:2000, a two-wave coupling gain of nearly 500 was obtained, which is much higher than the gain previously reported. Modified coupled-wave equations that involve beam fanning with certain assumptions concerning the fanning parameters were used. The numerical solution is in good agreement with the experimental data. The results are compared with those obtained with a 45 degrees -cut BaTiO(3) crystal.
通过在信号光束保持非寻常偏振的同时采用泵浦光束的最佳偏振取向，我们利用光折变掺铈铌酸钾钠锶钡（Ce:KNSBN）改善了两波耦合放大以及放大信号的信噪比。在对称入射系统中，通过实验发现泵浦光束相对于非寻常偏振方向的最佳偏振角为30度。在信号与泵浦光束强度比为1:40时，增益提高了近1.9倍，信噪比提高了近3倍。在光束强度比为1:2000时，获得了近500的两波耦合增益，这比之前报道的增益要高得多。使用了经过修改的耦合波方程，该方程在对扇形参数做了某些假设的情况下考虑了光束扇形化。数值解与实验数据吻合良好。将结果与用45度切割的钛酸钡（BaTiO₃）晶体所获得的结果进行了比较。
