Generally DPSS has enough gain that you can align it using the transmitted pump light / pre-lasing light and a B/W ccd camera. In some cases at least. Overlap the reflected spots, is what you do..
Usually I use an old CCD camera from the security business with the short lenses used for watching cash boxes in grocery stores, a lens extender ring (5$) and a USB frame grabber on my laptop.
That can be put together for less then 75$ with careful shopping on Fleabay / Amazon or a call to your local security camera installer who usually has no market for old 640x480 "C" mount CCD cameras... Just make sure the lens has a good iris that fully closes or gets near to fully closed. IR photons are "Bright" on camera.
The first time you align a laser can take hours or days... I know I had quite a learning curve for two and three mirror systems when I was young.
Can you shoot a picture of the whole resonator and post it?
I'd skip the fiber coupling on the HENE unless I was really getting desperate. I would suggest having two mirror mounts with 80 pitch screws, a piece of 80/20 (or similar) T slotted rail to set a round hene head in. The radius of the HENE head sets in the long groove on a typical round hene. Then some optical posts to mount the mirror mounts on. Generally two mirror mounts let you get the HENE beam to almost any height and azimuth you need. One Inch T-slot makes a good mount for round HENEs, they set in in the slot and a couple of wire ties hold it in. I have many of the commercial HENE mounts, and they are not on my alignment system. I made a three point stand using the T-slot and some 1/4" x 1" aluminum bar-- its a long "tee" shape. At the long end and at the ends of the cross bar are 1/4-80 screw sets from Thorlabs. Thus I can set the beam height , level the beam, and add in some tilt if needed.
We put orange stickers on the end of the HENE and use a sewing needle or similar to punch a hole in the sticker for the beam exit. Then you can see the dim red ghost beams come back off the optics to be aligned on the sticker.
Start with three Thorlabs N80L6P and appropriate length screws (longer is better) if you want to build an alignment jig this way. Skip the temptation to go to a finer pitch... 1/4-80 holds up to dirt and grease in this case.
Take a look at Thorlabs RA90s as part of the mirror mount scheme.
Steve
Last edited by mixedgas; 05-20-2021 at 06:06.
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