As reported in elog2831, we adjusted AOM incident laser relative angle to AOM and achieved power scattered from 0-order to 1-order of only 6%. We suspected the alignment maybe the main issue since usually 20dBm RF power should be enough. To confirm this, I took the RF amplifier from TAMA ZHL-2, which has bandwidth of 1GHz and can accept incident RF power smaller than 15dBm. I used this RF amplifier to provide even larger RF signal to AOM and check whether we can have larger efficiency.

The ZHL-2 has a gain of 18dB for signal around 100MHz. So I used Anritz to provide 2dBm at the beginning, which passed through ZHL-2 and arrived at AOM. Using power meter (with 55mW incident on AOM), I measured AOM efficiency as a function of AOM applied RF power. The result is shown in Fig.1.

We can see that higher AOM efficiency was achieved by applying higher RF power. In addition, the increase of efficiency with RF power is still quite linear and not reaching flat region. Therefore, it should be confirmed that alignment is not the reason of low AOM efficiency. But a higher AOM efficiency is prevented by not being able to provide a higher RF signal due to device limitation.