狭窄激光光束在掺铁铌酸锂晶体中的双波耦合

研究了狭窄激光光束在掺铁铌酸锂光折射晶体中的双波耦合（TWM）现象。对双波耦合中的能量耦合效率ξ，衍射系数η和相移φg之间的关系给出了一个简化的推导。保留表面电荷时候的能量耦合效率是不保留表面电荷时的两倍。氩离子激光诱发的折射率变化很明显地降低了能量耦合效率和折射率，这些都揭示了光折变效应和双波耦合有着直接的关系。相位差从最初的π降低到最小值后，重新恢复到π，然后趋于稳定状态。这个结果表明了表面电荷和两相干光束导致的空间电荷场有着明显的联系，而空间电荷场通过普克尔效应导致了折射率的变化。

Two-wave mixing of laser narrow beams in Fe:LiNbO3 crystals

Two-wave mixing (TWM) of laser narrow beams was investigated in photorefractive Fe:LiNbO3 crystals. A simplified deduction of the relationship of the energy coupling efficiency ξ, the diffraction efficiency η and the phase shift φg were given. When the surface charge was preserved, the maximum values of the energy coupling efficiency ξ were about two times of that when the surface charge was removed. A refractive perturbation Δnb induced by an argon ion laser would reduce the energy coupling efficiency ξ and diffraction efficiency η apparently, that reveals that the photorefractive effect has direct relationship with TWM about the phase shift φg, it initially decreased from π, after reaching a minimum, it regressed to π again when it went to steady state. The results clearly showed that the surface charge field has clear relationship with the space-charge field created by the two coherent beams, which induces space variation of refractive index via Pockels effect.