Shaping of dark beams in resonators with a bi-lens reflector

A laser resonator configuration is proposed in which the fundamental oscillating mode is an odd mode with a line singularity. The resonator is based on the replacement of one reflector by a bi-lens split mirror. The beam emitted by such a laser is an ideal source for the recently introduced singular beam microscopic procedure. We numerically investigate resonators with convex and concave faces of the reflector. It is shown that resonators of the latter type of reflectors have higher effectiveness in shaping modes with linear singularity. Their selectivity is also higher, than resonators with roof-mirrors that were investigated earlier.