Nonlinear optic devices

Remarkable nonlinear optic effect can be observed in optical waveguide due to optical high-power density with a long interaction length. We have been mainly studying optical second harmonic generation (SHG) in dielectric and organic waveguides. Waveguide SHG devices enables us to realize compact coherent-light sources in the short wavelength region. The LiNbO3 SHG devices consist of a optical channel waveguide and a ferroelectric-domain-inverted grating, which compensates phase-velocity mismatch between pump and SH waves for high efficiency. We have found and developed several techniques for the grating formation. And we have demonstrated efficient devices for blue/green light generation. Waveguide SHG in nonlinear organic materials, such as mNA, MNA, and so on, is also attractive because of their remarkably large SHG coefficients. We have fabricated organic single-crystal waveguides and examined SHG characteristics. Application of organic polymer materials to waveguide devices have also been studied.

Fig.15 Ferroelectric-domain-inverted grating of 3micron period for LiNbO3 waveguide SHG device.

.Fig.16 LiNbO3 waveguide SHG device with fan-out domain-inverted grating.

.Fig.17 Blue light generation by frequency doubling of laser-diode light in LiNbO3 waveguide SHG device.

Fig.18 Cross-Nicol photograph of a mNA(meta-nitroaniline) single-crystal waveguide.

Fig.19 Chemical structure and refractive indices of a poled polymer p-NAn-PVA.