Dear Sir,

I am doing the three beam laser interference lithography with 355nm laser.
My problem is that resulted pattern was partially interferenced. This
becomes more obvious when the period goes to the smaller values like 400nm.
I know here the polarization and distance is very important. The distance I
am sure that was controlled very well. But for the polarization, I am not
sure how can I set the best value, for example, the co-angle setting at 45
degree.

Is there anybody who could give me any suggestion on how to work it out?

Thank you very much.

Cheng