Hi all,
TL;DR: Any suggestions for a photodiode which
presumably InGaAs),
- and fits into a 4 mm deep (along direction of incidence) slot including connections?
critical here. Ge might be problematic in terms of dark current, though.
???
Now, for some context: A while back, I designed these amplified photodiode modules for intensity stabilisation/monitoring of collimated laser beams in my lab. The sensor is a Hamamatsu S6775 Si PIN diode, reverse-biased to ~14 V and bootstrapped with a Hobbsian JFET/PNP circuit (RIP, BFT92!).
I'm fairly happy with the design and bandwidth and noise are adequate for the application (~1 MHz at 2 M?, ~75 MHz at 3.2 k? ? the switchable gain was a bit tricky to get right). While it works beautifully in the blue, rather annoyingly the response at my two longest wavelengths, 1033
don't think there is anything nefarious going on beyond the textbook carrier diffusion time constant; still, this is a bit annoying, as the rest of the system has ~500 kHz bandwidth.
The obvious solution is to use a different sensor material for those NIR beams, e.g. InGaAs or Ge. I'd really rather re-use the mounts designed for the S6775 though, so the height of the diode needs to be < 4mm, which rules out most of the typical TO-? metal-can packages. I also need a fairly large active area, at least 1 mm^2 or so, as bodging any focussing optics into my beam-splitter/photodiode assemblies would be a pain.
My plan is currently to try and find an InGaAs photodiode in a thin SMD or COB package and mount it on a small carrier PCB to emulate the S6775's form factor. Hamamatsu's G11193-10R or G13176-010P would be an option, but there might be better alternatives I'm not aware of. Roithner Lasertechnik sells a near-ideal part as LAPD-3-09-17-LCC, but the >$450 price tag is a bit steep even for this low-volume application (maybe 10 pcs. in total over the next few years).
Thanks!
? David