Increased spectral bandwidths in nonlinear conversion processes by use of multicrystal designs

The fourth-harmonic generation of broadband 243-nm radiation is reported. The broadband radiation is achieved by implementation of a multicrystal design to overcome spectral bandwidth limitations, and a plane-wave analysis is developed that shows increased spectral bandwidths for these designs. The fourth harmonic of a Cr:LiSAF laser operating at 972 nm is generated in beta-barium berate (BBO). The results demonstrate a spectral bandwidth at 243 nm more than five times broader than that which is expected from a single BBO crystal of equivalent length. (C) 1998 Optical Society of America.