# Acousto Optical Modulators

1. Mar 1, 2012

### Niles

Hi

I have a question on AOMs used in a double pass configuration. I understand the motivation for such a setup, but what I don't quite understand is the following: During the first pass, the frequency of the incoming beam is changed from ω to ω+Ω at an angle θB. Then we send the diffracted beam with frequency ω+Ω through the AOM once again at the same angle θB. This last part I don't quite undertand: How can the Bragg condition be satisfied for the angle θB at both ω and ω+Ω?

Best regards,
Niles.

2. Mar 1, 2012

### The_Duck

I think the idea is that in general Ω << ω, so the correct angle is essentially the same for the second pass as for the first.

3. Mar 1, 2012

### Niles

Ah, I see. I thought it was most likely something like that, but I was worried that I had misunderstood something. Thanks for taking the time to reply.

Best regards,
Niles.