3 ) the quantum noise characteristics of the output of tropo are theoretically analyzed and the intensity - diflerence squeezing of two down - conversion beams was experimental obtained . the intensity - difference noise reduction was 0 . 4db 第三章：讨论了三共振光学参量振荡器的量子噪声特性，并实现了两下转换光之间的强度差压缩，压缩度达0 . 4db 。
