Modes of resonators with conical reflectors

Shaping of the oscillating mode within a laser resonator is useful for generation of special beam structures for applications such as metrology, particle manipulation, lithography, and energy delivery. It can also increase the power efficiency of the laser. Here we numerically study laser mode structures imposed by replacing one resonator mirror with a conical reflector. In the region with positive cone angles, the resonator radiates a flat top mode with enlarged mode volume inside the cavity that is capable to increase the power efficiency of the laser by a factor of 4-5. Pure oscillation on two azimuth modes can be obtained with a conical reflector of negative angle. Laser beams from such resonators are applicable for singular beam metrology and particle manipulation. Optimal parameters for generating these modes are derived. The best performance can be obtained in resonators with a configuration close to concentric.