The crossed Porro prism configuration improves the stability of the alignment of the laser resonator; however, the resultant phase shift alters the characteristics of the electrooptical Q-switch. An analysis of the operational characteristics, such as variable outcoupling, extinction ratio, and prelasing boundaries, is presented along with experimental data. An electrooptically Q-switched Nd:YAG laser with a crossed Porro prism resonator, which successfully withstands severe physical environments, has been developed and demonstrated.
M. K. Chun and E. A. Teppo, "Laser resonator: an electrooptically Q-switched Porro prism device," Appl. Opt. 15, 1942-1946 (1976)