LIGO Document T1000574-v1
- The AOM/EOM driver is a high power RF amplifier used to drive an eletro-optic modulator [EOM] or an acousto-optic modulator [AOM] for Advanced LIGO. It provides up to 2W of RF power adjustable over a 24.2dB range, from 10 dBm to 34.2 dBm. It has an amplitude stabilization circuit to minimize the oscillator amplitude noise. The main structure of the present design consists of a radio frequency [RF] chain with a 12 dBm source input, a voltage-controlled attenuator, a high power amplifier and two in series directional couplers. For RF AM stabilization, there is an in-loop and an out-of-loop circuit. The in-loop circuit includes an RF detector, which is fed by the first coupler and connects an RF servo to control the voltage-controlled attenuator. This detector can accurately measure the RF noise and remove unwanted noise. The out-of-loop circuit has an independent RF detector to verify the AM noise after the stabilization.
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