So the parts for the first prototype are here but the boards will take a bit more time.

When I broke open the box, I took a good look at the pin diode. Though its rather comparable to commercial detectors it is a bit smaller.

The diode would be easier to use if it were larger area, the problem is that area costs money (and dark current). 60-100 dollars a sensor would get a 30 sq. mm to 100 sq. mm detector. This being an order of magnitude more isn't that appealing. Nevertheless it is possible.

I also note that in the smaller detector realm there is a reasonable choice from Thor Labs that you can get with a NIST calibration ($$$) or without (reasonable). It might be interesting to build a version compatable with that footprint to gain a NIST traceable result.

Probably the better solution to the size of the detector is just to use single convex lens. The system will already be compatible with a lens tube and thus one can get an effective diameter of 25 mm if a lens is used (presuming the laser is reasonably collimated coming in). Using a lens does introduce another offset/loss to correct for, but that loss is published and so should not be too hard to remove either.

It will be interesting to see what kinds of calibration and accuracy I can develop with this detector when the boards arrive.