Gain guiding in an old concept used in gas lasers1,2 and semi-conductors lasers. The idea is to used the gain gradient that is established when a laser medium is pumped by another laser, to concentrate the energy on the resonator axis. This guiding effect can be used in conjunction with an unstable resonator to fill the gain region. Since there is no hard aperture the energy can be extracted efficiently, while preserving good beam quality. This type of resonator is very similar to unstable resonators using a VRM, with the difference being that the gain medium becomes a gaussian aperture which can be adjusted in size by changing the pump beam diameter. Recently, S alin and Squier3 have introduced the idea that the gain guiding effect, induced in a solid-state medium pumped by a laser beam, can be used to produce high quality beams of arbitrary large diameter from unstable resonators.
© 1993 Optical Society of AmericaPDF Article