Thanks for your honesty, Andy-- Even deciding that it's not possible I think is a useful result! I'm willing to accept that we can't do better than Luc's original design, but I'm finding this exercise useful in helping me understand what the tradeoffs are in Raman spectroscopy.
I tracked down Luc's comment regarding eBay lasers:
Cheap e-bay lasers are not an option in that regards because they are a lottery: very few ones will have correct performances but most of them will be crappy or even dangerous to operate
I've also found this to be true. The cheap CO2 laser I use for laser cutting seems very
, shall we say, handmade. If it didn't operate inside of a large metal box, I would be too nervous to use it.
However, sources suggest that Luc has perhaps found a quality laser candidate in the $150 range. If it pans out, I think the dream of a super-low-cost OpenRAMAN spec lives on.
The way forward would probably be to Luc's suggestion of manufacturing a probe through CNCing then using external tooling to align the lenses with glue to set them. I just don't have the skill or capability to do that. Hubs can do the cncing cheaply but you have to put in a large order.
I have a CNC mill and would be happy to make parts as needed. I'm limited to aluminum, but it could work. I'd also be happy to experiment with designing tooling to align the lenses. This seems like a potential task for SLA 3D printing, but I admit I don't understand the problem space well enough to offer solutions just yet. Perhaps sometime we can brainstorm ideas on how to perfect the alignment process.
This would just leave the final piece, which finding the correct sensor. Wisdom of the masses indicates that the TCD1304 will work, but perhaps we can do better. Can we design an SMA input for this sensor? Perhaps this already exists on AliExpress... https://www.aliexpress.us/item/22518327 ... 4itemAdapt
It's not clear to me how to compare a chip like the TCD1304 to a purpose-built spectrometer like the C13054MA mentioned in our earlier email thread. (https://www.hamamatsu.com/content/dam/h ... c1233e.pdf
). Maybe apples to oranges?
At the end of the day, it's a question of how many Raman-scattered photons reach our sensor, and how likely it is that those photos interact with the CCD itself. There are some software tricks that we can use to improve the results, but physics is king in this application.