# Semi-classical argument for stimulated emission?

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1. Sep 22, 2015

### Michael Lazich

Laser action by definition requires the presence of stimulated emission in the laser medium. The typical way of treating this semi-classically is to introduce the Einstein coefficients, in essentially an ad hoc way, then derive the Einstein equations for the various level population transitions.

My issue is that the various arguments I've seen for explaining the presence of the stimulated emission term are rather unsatisfying, until you're actually able to show quantum mechanically what is going on.

That is, it's somewhat "intuitive" to discuss stimulated absorption (i.e., photon of proper energy is absorbed by atom causing an upward transition to a specific higher energy state), and spontaneous emission (fluourescence), but there doesn't seem to be a similar argument about stimulated emission short of the QM treatment.

Of course, stimulated emission *is* inherently QM, so there really isn't necessarily a non-QM argument or model for it; but I'm curious if others have thought of semi-classical models/explanations (than those available in, say, Siegman) that could help build a sense of "physical intuition" around the concept.

Thanks.

2. Sep 22, 2015

### Michael Lazich

Should have checked before I posted, I think this has been brought up in earlier threads...

Not sure how to delete though; apologies for redundancy.