90°全息记录衍射效率分析与提高

对光折变全息记录特别是双中心全息记录中90°记录结构下较低的衍射效率进行了研究, 采用局域衍射理论对90°记录结构的衍射进行了分析,表明在同样的折射率变化和2 mm的光束宽度的情况下, 只有当折射率光栅振幅大于10-4时, 90°记录结构衍射效率才能够与小角度透射记录结构的衍射效率大致相当。针对环境干扰导致的干涉条纹振动影响光栅记录, 提出了有效调制度概念, 根据分析90°记录结构的干涉条纹间距很小, 容易受外界环境干扰而导致低的折射率变化率, 因此应采用主动条纹锁定系统。此外在双中心全息记录中, 微观光

The relatively low diffraction efficiency of photorefractive holographic recording, especially that of the two-center holographic recording with 90° geometry, is studied, based on the theory of local diffraction. It shows that the diffraction efficiency in 90° geometry can be comparable with that in transmission geometry only when the amplitude of refractive index gratings is more than 10-4 with the same refractive index change and beam width of 2 mm. According to the effects of fringe vibration caused by environmental perturbation on holographic recording, a concept of effective modulation is proposed. Narrow grating space in 90° recording geometry makes it more sensitive to ambient disturbs and leads to low refractive index change. To obtain high diffraction efficiency in experiments with 90° geometry, an active fringe stabilization system is necessary. Furthermore, in two-center holographic recording, the effects of microcosmic optical parameters on diffraction efficiency are also important.