Continuous narrowband lasing with coherently driven V-level atoms

Simultaneous strong coherent pumping of the two transitions of a V-level atom with very differentdecay rates has been predicted to create almost perfect inversion on the narrower transition. Usingthe example of the blue and red transitions in Strontium we show that for suitable operatingconditions the corresponding resonant gain can be used to continuously operate a laser on thenarrow transition. In particular, for a strong detuning of the pump field with respect to the narrowtransition, coherent laser emission occurs close to the bare atomic transition frequency exhibitingonly a negligible contribution from coherent pump light scattered into the lasing mode.Calculations of the cavity output spectrum show that the resulting laser linewidth can get muchsmaller than the bandwidth of the pump light and even the natural linewidth of the narrow atomictransition. Its frequency is closely tied to the atomic transition frequency for properly chosen atomnumbers. Simulations including atomic motionshow Doppler cooling on the strong transitionwith minor motion heating on the lasing transition, so that continuous laser operation in thepresence of a magneto-optical trap should be possible with current experimental technology.