I started dissecting a flash-pumped crystal laser recently. I can identify pretty much everything on the inside (mirrors, active shutter, fiber-coupling optics, laser cavity with flash tube, etc), but one part is really puzzling me.
The laser cavity (shiny box at the center of the assembly) is mounted to this peculiar block, with many pictures below. I carefully took it apart hoping to find a model number hiding somewhere, but no dice.
What I know:
* Made of a hard insulating plastic, possibly delrin.
* A couple
electrical components potted on the inside.* Box has a
single SMA connection. It was routed to to the outside of the laser assembly with an SMA extension, so it's probably relevant.
* SMA connection has a
DC resistance of ~0.2 ohms. Below the reasonable bounds of my multimeter.
*
Resonant frequency of ~250 kHz when stimulated with a function gen and measured with a scope. At this frequency, input attenuation is ~0 dB.
* Strange
metal nub is electrically relevant, has a voltage ~50x the input voltage at the resonant frequency.
*
Metal nub electrically contacts the aluminum laser cavity. The nub has some give to it, sticking out of the plastic when the cavity is removed, but recesses back down as force is applied. This doesn't affect the resonant frequency (but electrically contacting it with my finger does).
* There's
nothing interesting on the inside of the cavity near the nub. It's just hollow and has the flash tube.
Quite an information dump, but I'm quite stuck here (and so are other people I've asked about this). I want to know the purpose of it, and what it's role is in this laser.
Scope shot shows a frequency sweep from 100 kHz to 20 Mhz (log scale over time, 14 seconds), amplitude 0.5 vpp. Yellow channel is the input at the SMA. Pink channel is me holding a probe on the metal nub. Note the 50x difference in channel scalings. Resonant peak is ~250 kHz.
Any semi-relevant information or suggestions of further tests would be appreciated