Laser cooling was an interesting thing in David Brin's sci-fi novel Sundiver [1].

[1] https://en.wikipedia.org/wiki/Sundiver

What are the applications?

A direct one is a thermometer, but I think a much more interesting one is a possibility of cooling things with a laser.

You shine laser on something with strong anti Stokes luminescence, and cool it by having reemitted photons carrying away more energy from an object than being absorbed.

Along the same lines, I suspect an efficient enough gas dynamic laser can be coerced into working as a heat pump. If true, that can revolutionize cooling in spacecrafts: ISS have to carry huge radiators weighting almost as much as its solar panels; imagine replacing them with relatively small lasers.

I've long thought that beamed power to spacecraft might be combined with laser cooling to achieve very high power/mass, which is needed for simultaneous high acceleration + high Isp.

How would the cooling help?

Any high Isp propulsion system is limited by the dissipation of waste heat and the need to radiate it. The mass of the radiators limits the acceleration. This is the defining difference between real spacecraft and Hollywood spacecraft.

Hmm. Could be used to adjust the trajectory of asteroids?

I think just changing their trajectory with much easier kinetic means will work just fine.

This could be very useful in photonics chips for ICT. Thermal management is a huge problem in this area.

Eli5?