1. E. Yablonovitch, Phys. Rev. Lett. 58, 2059 (1987).
2. See, for example, J. Lightwave Technology 17 (11) (1999), which is one of the most recent feature issues of photonic crystal, and the references therein.
3. S. J. Smith and E. M. Purcell, Phys. Rev. 92, 1069 (1953).
4. For the recent works on Smith-Purcell effect, see, e.g. J. H. Brownell, J. Walsh, H. G. Kirk, et al., Nucl. Instrum. Methods Phys. Res. A 393, 323 (1997); O. Haeverle, P. Rullhusen, J.-M. Salome, and N. Maene, Phys. Rev. E 55, 4675 (1977); J. H. Brownell, J. Walsh, and G. Doucas, Phys. Rev. E 57, 1075 (1998).
5. For the SP radiation as a coherent light source, see, e.g., Y. Shibata et al., Phys. Rev. E 57, 1061 (1998) and the references therein; For the radiation from SEM involving induced emission, see, J. Urata et al., Phys. Rev. Lett. 80, 516 (1998).