Transition to lasing induced by resonant absorption

We theoretically demonstrate that increase of absorption with constant gain in laser systems can lead to onset of laser generation. This counter-intuitive absorption induced lasing (AIL) is explained by emergence of additional lasing modes created by an introduction of an absorbing medium with narrow linewidth. We show that this effect is universal and can be encountered in simple Fabry-Perot-like systems and doped spherical dielectric nanoresonators. The predicted behavior is robust against frequency detuning between the gain and absorbing medium

Nanostructured optical waveguide with a highly confined mode

We propose a transmission line working at telecom wavelengths with cross section as small as ${\lambda}^2/39$, which is 1.6 times smaller than that of optimized silicon waveguide. The proposed line can be implemented as a subwavelength fiber with plasmonic cladding. This considerable decrease in the line cross section is achieved by utilizing a plasmonic quasi-antisymmetric mode. The required plasmonic cladding is rather thin, therefore, losses are moderate and could be compensated by using amplifying core materials. Such a transmission line can find applications in densely integrated optical systems

Channel spaser

We show that net amplification of surface plasmons is achieved in channel in a metal plate due to nonradiative excitation by quantum dots. This makes possible lossless plasmon transmission lines in the channel as well as the amplification and generation of coherent surface plasmons. As an example, a ring channel spaser is considered