Abstract

In the fifties Schawlow and Townes showed that the quantum-limited linewidth of a four-level laser with low out-coupling is inversely proportional to the laser’s output power P_out and directly proportional to the square of the cavity loss-rate Δυ_cav = − (c/2L)ln(R₁R₂), where R₁ and R₂ are the mirror reflectivities and L is the cavity length. Today this basic statement still holds and serves as a reference point but has been extended to account, e.g., for high-outcoupling and incomplete inversion.

© 1994 IEEE