Diode pumped laser using crystals with strong thermal focussing

摘要

A diode pumped laser includes a resonator mirror and an output coupler, defining a laser resonator with a resonator optical axis. A strong thermal lens laser crystal with a TEM.sub.00 mode diameter is mounted in the resonator along the resonator optical axis. A diode pump source supplies a pump beam to the laser crystal in the laser resonator, and produces an output beam with a diameter larger than the TEM.sub.00 mode diameter to reduce thermal birefringence. A power source supplies power to the diode pump source. A polarizing element can be positioned in the resonator, along with a aperture stop The laser operates well over a large range of pump powers. Its slope efficiency in the TEM.sub.00 mode is greater than 40%, with an overall efficiency greater than 25%. One of the lasing crystals used is Nd:YVO.sub.4. This material exhibits high gain and a short upper state lifetime. These properties make it attractive in designing a Q-switched laser, or one that is insensitive to optical feedback. Another material is Nd:YAG. The technique of optimizing the pump beam spot size is found to minimize loss due to thermal birefringence.