Laser Linewidth - Githubissues

OxfordIonTrapGroup / atomic_physics

Nascent toolkit for calculating state energies, transition matrix elements, rate equations, obe solver, etc

17 stars 17 forks source link

Laser Linewidth #17

Open pathfinder49 opened 4 years ago

pathfinder49 commented 4 years ago

Currently the package assumes lasers to have infitessimal linewidth. This seems reasonable, given the current package feature-set.

When moving to more advanced (optical bloch equation) simulations, laser linewidth may become relevant.

Laser cooling, readout, etc.: laser linewidth should be negligible when driving E1 transitions.
Dark resonaces: laser linewidth may become important with lower laser intensities. However, I expect our cooling scheme to be outside this regime due to large laser powers.

RHanley1 commented 4 years ago

I think with our expected laser linewidths of ~300kHz, I wouldn't worry about it for now. Just focus getting everything else working. Laser linewidths can be added rather simply later on in a phenomenological way whereby an extra dephasing is introduced on the coherence's between connected levels.

hartytp commented 4 years ago

Agreed: don’t bother with them for now as we can add a dephasing term later.

FWIW the effective laser linewidth is broadened by the ions motion. Eg around a dark state the ion gets an oscillating Doppler shift that introduces scattering. It’s even more complicated when the d states are introduced as the repumping time can be long. So when the ion reaches the d states the scattering ceases for a while and then re begins with an essentially random phase. It’s messy (see the paper we wrote on this).

In practice we’ve tended to add an empirical dephasing factor that we tweak to make the sims match the data.