See my overview video of the cavity, demonstration of tuning it up and operation in the video: 

I put my 3D design files (STLs & STEPs) up on github: https://github.com/wildcircuits/3DPrintedOpticalCavity

This is a simple design with 2 50% reflective front surface mirrors.  The back mirror is mounted to a speaker which allows for fine adjustments to the length of the cavity.  In the video I demonstrate a sine wave on the speaker that results in 325nm of movement, the distance between 2 cavity resonances for a 650nm laser!

I iterated through several different laser sources and landed on a 'visual fault locator' that couples a red (650nm) laser to a single mode fiber.  This is nice because it cleans up the laser spot into a nice circular beam.  The single mode fiber is made for 1550nm communications so it has a 9um diameter.  This means it is actually passing multiple modes of my red laser but it was cheap and good enough for me.

I didn't go into details on the tip/tilt adjustable mounts in the video, but they are built around a ball bearing for the joint allowing movement in the 2 axis.  Two 6-32 1" thumb screws are used for input and a rubber band keeps the system tensioned.  I've found this to work very well, but my initial attemps at just tapping the 6-32 threaded hole in the print weren't as precise as I'd like so I switched to heat-set threaded inserts.  They work great.