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Acousto optical modulators 
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#1
Feb912, 03:24 PM

P: 1,863

Hi
Say I am looking at an AOM working in the Bragg regime (i.e., only a single diffracted beam). It is easy to show using Bragg's law that the frequencyshift Ω of the diffracted wave is given by [tex] \Omega = 2n\omega \frac{v}{c}\sin(\theta) [/tex] Here Ω is *also* the frequency the AOM is driven with, in other words the LHS is constant in the sense that in does not depend on the incoming light (so the frequencyshift imparted on the wave is constant). However, the RHS does depend on the incoming light, since the angle θ of the diffracted beam is equal to the angle of incidence of the incoming beam, so I can change it easily by e.g. turning the AOM. In my book it says that the shift Ω is zero for forward scattering and maximum for backscattering. This is what I don't understand: The shift Ω is the same as the frequency of the phonons in the material, which is *constant*. So how can I change the frequency shift of the diffracted wave by changing the angle on incidence? Best, Niles. 


#2
Feb1012, 02:47 AM

P: 1,863

OK, I understand my error now.



#3
Feb1012, 07:18 AM

Sci Advisor
P: 5,510

What book are you using? I have one by Korpel, and it's not working for me...



#4
Feb1012, 01:05 PM

P: 1,863

Acousto optical modulators
I am using Boyd's Nonlinear Optics, it has a nice chapter on spontaneous lightscattering including Acoustooptics. I hope it works out.
Best, Niles. 


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