Two regions of mode selection in resonators with biprismlike elements

A resonator structure in which one reflector is replaced by a biprismlike reflecting surface is investigated theoretically. It is shown that such a modification leads to two regions of parameters, each with different regimes of mode selection. The first region has an improved laser power output because of the nearly flat-top mode shape. In the second region the biprism is inverted, with the result that the main oscillating mode can be the first odd mode. The line singularity contained in such a mode is one example of singular beams that are employed in various fields, such as micromanipulators and advanced high-resolution metrology.