Then we turned in the input laser to observe the decline of phase conjugate reflectivity . measuring dark storage time , we found that the phase conjugate reflectivity declined to 50 % of steady - state value when photorefractive crystal was in dark condition for 30 minutes . even after 9 hours , there still existed remaining reflectivity , which could n ' t be measured by our detector 因而研究了晶体内位相共轭光栅存储特性，即观察位相共轭光栅形成后在黑暗条件下能存储的时间，实验结果得出位相共轭光栅在黑暗中30分钟后，位相共轭反射率下降到原来的50 ，而在黑暗中9小时后，位相共轭光非常微弱，无法测出。
