The light is immaterial (lol) to the holograms existence. They are only solid via fancy forcefield transmitted from the holo emitters. For all intents and purposes they seem to only exist as programs within whatever computer operates the holo emitters, whatever or whatever that may be. The only limit on where they can be is the speed of the computer system and links within it. They can send holo programs between the alpha and delta quadrants, but are limited by the speed and this can only send smaller programs. The mobile emitter often gets transported, but that’s because they only have one. If the doctor is going somewhere with holo emitters they don’t need to be transported and can just be data transferred.
Personal rant follows:
!The whole hologram plot in Voyager is honestly poorly thought out, and it basically feels like if you followed their logic Chat GPT would be a protected federation citizen. I get that the writers wanted to give the doctor legitimized personhood, but it feels like they forgot to think about what that would mean for literally every other hologram. !<
!Like, they give that one species holograms to hunt, does that mean they invented a species doomed to be reincarnated as prey forever? Is, Moriarty sentient, and if so is trapping him in a simulation moral? If they just run a hologram long enough does it gain sentience? How are they testing for this? Does that mean Vic Fontane is sentient even though he probably would say he isn’t? What about that weird Irish bartender Janeway does - fair haven ran for a while, how long does it take? If you run a training program are you committing infanticide? Is turning off a hologram even moral?!<
No, that’s why the baby fridge works. The peltier TEC in the fridge can produce temperatures below ambient, but generally not below freezing. Computer chip TEC coolers would go farther and push more power through the TEC and do things like water-cooling the hot side instead of a little fan.
The reason they don’t get used anymore more complicated. It’s my understanding that basically TECs have a sort of limit on the amount of heat they can push from the cold side to the hot side, because moving more heat means more energy used and thus more waste heat. Apparently most modern chips are past that limit. IIRC, TECs can only move something like 100w of heat - past that and they start to heat themselves up because of waste heat. Modern chips can be like 300w.
Sub ambient cooling also comes with a bunch of issues like condensation, so no one really uses it day to day. Also, chips are run so close to their limits now that cooling like that doesn’t get you nearly the performance difference it once did.