Transition to Lasing Induced by Resonant Absorption

Denis Baranov Nanoplasmonics Group, All-Russia Research Institute of Automatics, Moscow, Russia Department of Physics and Power Engeneering, Moscow Institute of Physics and Technology, Dolgoprudny, Russia Igor Nechepurenko Nanoplasmonics Group, All-Russia Research Institute of Automatics, Moscow, Russia Department of Physics and Power Engeneering, Moscow Institute of Physics and Technology, Dolgoprudny, Russia Alexander Dorofeenko Nanoplasmonics Group, All-Russia Research Institute of Automatics, Moscow, Russia Department of Physics and Power Engeneering, Moscow Institute of Physics and Technology, Dolgoprudny, Russia

It is generally assumed that an increase of loss in a laser system leads to decrease of lasing intensity and, eventually, makes laser turn off. On the other hand, it is also widely accepted that increase of gain correspondingly increases laser radiation intensity. This naive picture stems from the primitive single-mode rate equations, which are often employed for description of laser operation. Nevertheless, behavior of lasing modes can be much more complicated. Particularly, it has been reported recently that increase of pump intensity in a laser system with non-uniform gain distribution makes the laser turn off [1]. Importantly, such unusual behavior relies on spatial variation of the gain profile. Finally, in a recent experimental work the counterpart of lasing shutdown was observed: authors reported that adding spatially distributed loss in a pair of coupled whispering gallery mode resonators may increase lasing intensity [2].

In this paper, we show theoretically that increase of loss in a laser system brought by a dispersive absorbing medium can lead to emergence of lasing. In contrast to experiment by Peng et al. [2], spatial inhomogeneity of loss or gain distribution is not required in our configuration. Instead, the predicted phenomenon of absorption induced lasing (AIL) is related not to geometry of the system, but to frequency dispersion of the resonator medium. Within the framework of scattering matrix formalism, we encounter this effect in a simple toy system, consisting of a planar slab made of a uniform mixed loss-gain medium. Absorbing medium induces new system of S-matrix poles corresponding to quasistationary modes. With increase of loss, these additional modes evolve and begin to lase. We also predict AIL in an alternative spherical nanoresonator which is free of certain unwanted effects that may occur in planar laser cavities.

[1] M. Liertzer et al, Physical Review Letters 108, 173901 (2012).

[2] B. Peng et al, Science 346, 328 (2014).

baranov.mipt@gmail.com