A new organic crystal isopropyl-4-acetylphenylurea (IAPU) was identified as a promising candidate for blue second-harmonic generation (SHG). The nonlinear optical d coefficient obtained is d<sub>22</sub>=30.5 pm/V at the fundamental wavelength 1064 nm, and the crystal's transmitting range is 380–1400 nm. Thin, single crystalline films fabricated on the glass substrate are useful for waveguide-device applications. For the improvement of SHG efficiency and the relaxation of phase-matching conditions, the concept of thickness-noncritical phase matching (TNCPM) in a four-layer waveguide is proposed. Modal dispersion calculations for the various four-layer structures suggested the possibility of TNCPM from the TE<sub>0</sub><sup>ω</sup> mode to TE<sub>1</sub><sup>2ω</sup> mode and from the TE<sub>0</sub><sup>ω</sup> mode to the TE<sub>2</sub><sup>2ω</sup> mode by adjustment of the refractive indices of the two guiding layers.
© 1997 Optical Society of America
H. Yamamoto, S. Funato, T. Sugiyama, J. Jung, T. Kinoshita, and K. Sasaki, "Organic crystal isopropyl-4-acetylphenylurea and waveguide second-harmonic generation," J. Opt. Soc. Am. B 14, 1099-1108 (1997)