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KTP Crystal Mount: How Many Degrees of Freedom?

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Laser
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198
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2023-02-23

Most of the designs I've seen for a KTP crystal mount allow X / Y angle along with rotation. I've built such a mount and in my testing I didn't find the X / Y angles to make much of a difference. Do they under certain circumstances? Crystals I've seen are cut to work parallel to the optical axis. Is flexibility here just done to account for imperfect beam alignment since the acceptance angle is quite narrow? My mount used the back end of a mirror mount for X/Y angle and adjusting it didn't make much of a difference unless I was way off parallel.

 

I'm asking because I'm in the process of re-designing this crystal mount and it would be much easier to temperature control if I had a nice rigid connection to the optical table.

 

 

C

    • Henry

      2023-02-24
      I think all 6 dofs are important.
Having translation makes it possible to use a different spot of the crystal if the coating ever gets damaged.
Z-translation might be almost useless.
The crystal is often short compared to the rayleigh length having it not precisely centered should make almost no difference in crystal volume usage.
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        • Henry

          : Rotation (X/Y) does not need to be accurate but can be helpful to align or remove "ghost" spots that get generated by not perfect AR coatings on the crystal faces. Having a "ghost spot" close to the real output would bother me. Rotation (Z) is needed for polarization matching of the pump beam (depends on if your laser medium is actually sensitive to this).

        • Henry
          Reply
          @Henry

          : Using a L-bracket with oblong screw holes can give you 4DOF (X/Y rot+trans) already. Z Rotation could be accomplished by using a precision fit hole/bore. That gives reasonable thermal performance (with copper) while allowing all DOFs and being small at the same time.

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