Signal Amplification by Two-Wave Mixing in Dye-Doped Films

本文研究了在非线性光学介质（染料掺杂聚合物薄膜）中引入两束信号和泵浦光束时的自衍射现象。在两波混频中。两束相干光束在薄膜中相交，其中一束以牺牲另一束为代价而增强。通过在干涉图样和相位和/或吸收光栅之间引入相移来实现功率传输。在有机染料掺杂薄膜中，由于非线性光学材料的非零响应时间，两束光束中的一束的频移会产生移动光栅，从而导致相移。(1)对于饱和染料，归一化自衍射强度是两个分量的乘积：对两波的频率差OMEGA的反对称分量，这是由于折射率的色散，分别对ω > 0或ω <0的正失谐参数具有正或负指数增益，而对泵浦波的吸收产生的对称分量对所有ω具有负指数增益。(2)对于杂蒽染料和氮染料，当OMEGA = 0时，自衍射光束的强度比透射光束的强度最多增加几个百分点。(3)偶氮染料在两束光交叉极化的情况下也能观察到自衍射现象。(4)用非共振波长的高功率激光观察到放大现象。

The present work is concerned with observation of self-diffraction when two beams, signal beam and pump beam, are introduced into optical nonlinear media (dye-doped polymer films). In two-wave mixing. Two coherent beams intersect in the film and the one of them is enhanced at the expense of the other. The power transfer is performed by introducing a phase shift between the interference pattern and the phase-and/or absorption-grating. In an organic-dye-doped film, frequency shifting of one of two beams creates a moving grating and thus leads to the phase shift because of the nonzero response time of the nonlinear optical material.(1) For saturable dyes, the normalized self-diffracted intensity has a product of two components : the antisymmetric component with respect to the frequency difference OMEGA of the two waves, which is due to the dispersion of refractive index has a positive or negative exponential gain for OMEGA > 0 or OMEGA<0 for positive detuning parameter, respectively, and the symmetric one arising from absorption of the pump wave has a negative exponential gain for all OMEGA.(2) For xanthene dyes and azine dyes the intensity of the self-diffracted beam increased at most by several percent compared with that of the transmitted beam for OMEGA = 0.(3) For azo dyes, self diffraction was observed even when two beams were cross-polarized.(4) Amplification will be observed with a high power laser whose wavelength is off resonance.