Spaser in above-threshold regime: The lasing frequency shift

Operation of spaser-based nanolaser is considered theoretically. We establish that the dependence of the lasing frequency undergoes red-shift with the increase of the pumping intensity. We propose, that the mechanism leading to the red-shift is based on space deformation of the lasing mode, which is induced by inhomogeneous depletion of the gain media. We develop general analytical scheme which allows to account the mode deformation.