[simontheowl]

A large reason why these are aimed for scientific missions is because the single photon detectors utilized for receiving these transmissions are still incredibly expensive. They are basically liquid-helium cooled arrays of nanowires (SNSPDs) which act like micro balometers - pretty sweet tech, but not commercial grade just yet.

[linuxdude314]

Is there a reason you can’t use an avalanche photo diode biased in Geiger mode to achieve this?

If biased properly an APD can be used for single photon counting and they only cost $70-250, I’m just not sure if they hold up in space without modification.

[namibj]

The nanowire localizes the photons in space, time, and energy. APDs can't do energy.

The cryogenics allow using cryogenic-level bandgaps/carrier-energies, so each optical photon turns into many carriers which then flow out the wire in both directions, the delay between the pulse on both ends localizes the impact along the wire.

[sansseriff]

SNSPDs have lower dark count rate, and especially lower timing jitter in the near-infrared than APDs.

The deep space optical demonstrations I know of all work in the near infrared (e.g. 1550 nm), just like most of terrestrial fiber optics used for communication. Probably because there's lots of infrastructure at that wavelength already, and it's a good passband through earth's atmosphere.