I installed the another double-pass AOM — to be precise, I installed a lens, QWP, and mirror for composing double-pass AOM system.
The attached picture shows the installed optics.
The following is the procedure.
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Adjusted the alignment to maximize the -1st order diffracted beam power.
The diffraction efficiency was about 85%.
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Then put a lens (f=75mm) and QWP to collimate the beam.
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Put a mirror and adjusted the alignment to let the diffracted beam enter the AOM.
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Adjusted the alignment with two STMs and one end mirror by monitoring double-passed beam power.
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I got about 72% double-pass diffraction efficiency at the end.
I have not investigated the beam jitter of this system.
So I gonna measure the beam jitter with frequency scan and then install optics for ISS.