Hydrodynamic phenomena in laser physics: Modes with flow and vortices behind an obstacle in an optical channel

The transverse patterns of an active resonator with cylindrical optics are investigated. This resonator configuration corresponds to a ''channel'' form of the potential for the ''photon fluid.'' Simultaneous emission of different transverse modes along the channel, periodic nucleation of vortices in the form of a vortex street (vortices of alternating senses of rotation appearing in a flow behind an obstacle), accelerated flow in a ''tilted channel,'' and destabilization of the one-directional flow in the channel are demonstrated and interpreted in terms of tilted waves and beating of channel modes, as well as in fluid terms, illustrating the fluid dynamics correspondence of class-A lasers.