Transverse SBS. Consider the possibility of exciting SBS in the transverse direction by a laser beam passing through a fused-silica window at nearnormal incidence. Assume conditions appropriate to a high-energy laser. In particular, assume that the window is 70 cm in diameter and is uniformly filled with a laser pulse of 10-nsec duration at a wavelength of 350 nm. What is the minimum value of the laser pulse energy for which SBS can be excited? (In fact, transverse SBS has been observed under such conditions similar to those assumed in this problem; see, for example, Murray et al., 1989.)