Naota Uenishi

Structure and nonlinear optical properties of diacetylene thin films vapor-deposited on highly oriented polytetrafluoroethylene thin films

Five diacetylene compounds were vapor-deposited on a highly oriented thin film of polytetrafluoroethylene (PTFE) prepared by mechanical deposition. 1,6-Di-(N-carbazolyl)-2,4-hexadiyne (DCHD) film was composed of needlelike crystallites along the chain axis of the PTFE macromolecules. The DCHD crystal was oriented with respect to the PTFE crystal substrate in the relation of (100) * [010] DCHD //(100)[001] PTFE . Other diacetylenes also formed uniaxially oriented thin layers. Upon photoirradiation diacetylene films changed to polymer films having extremely high crystallinity and considerable in-plane dichroism. The third-order susceptibility X (3) of the miaxi-ally oriented polydiacetylene films were several times larger than those of the randomly oriented films. Crystal growth observed by electron microscopy on local and microscopic scales was confirmed by THG measurement on a macroscopic scale.

Frequency doubling of a Nd:YAG laser using a crystal-cored fiber of an organic 4-(N,N-dimethylamino)-3-acetamidonitrobenzene

Optical second-harmonic generation from a glass-clad fiber with an organic core crystal of 4-(N,Ndimethylamino)-3-acetamidonitrobenzene (DAN) is demonstrated. Phase matching was due to cerenkov radiation. Linear and nonlinear optical properties of DAN, a fabrication technique of a crystal-cored fiber, and a focusing method of the generated second-harmonic wave are studied.

Crystal Cored Fiber Using Organic Material And Focusing Properties Of Generated Second-Harmonic Wave

A single crystal-cored fiber using 4-(N, N-dimethylamino)-3-acetamidonitrobenzene (DAN) was fabricated. Single mode-propagation was achieved for dense flint glass cladding. The single ring-pattern of the second-harmonic wave corresponding to the singly guided fundamental mode was obtained and its conversion efficiency was 0.42% at the fundamental power of 29.3W. After collimation using an axicon lens, the second-harmonic wave from the fiber could be focused into a smaller spot than the usual light beam with a circular aperture.

Crystal Growth and Characterization of N-(5-Nitro-2-pyridyl)-(s)-phenylalaninol: A New Organic Material for Nonlinear Optics

Abstract Crystals of N-(5-nitro-2-pyridyl)-(s)-phenylalaninol having good optical quality were grown from solution. The crystal structure and the linear and nonlinear optical properties were determined. Angle tuned phase matching was achieved with a d eff = 31 pm/V and a conversion efficiency of 0.15% was obtained at the fundamental power of 50 kW/cm2 using a 0.45-mm-thick crystal.

Design, fabrication, and evaluation of crystal-cored fibers for efficient second-harmonic generation based on Čerenkov-radiation-type phase matching

A formulation for calculating the optical second-harmonic power based on the Cerenkov-radiation-type phase matching is derived for a crystal-cored fiber. The prerequisite condition for high efficiency is expressed by a simple relation by use of the refractive indices of a core crystal, a core radius, and a fundamental wavelength. An organic crystal-cored fiber is designed and practically fabricated by the guiding principle derived here. A blue second-harmonic wave of 1.4 mW is obtained from a 1-mm-long fiber by use of a 60-mW semiconductor laser, and the second-harmonic intensity agrees well with the prediction. Degradation of the organic core crystal caused by the generated blue wave is observed, and the lifetime of the device is evaluated.

Structures and nonlinear optical properties of 4-(N,N-dimethylamino)-3-acetamidonitrobenzene films prepared by vapor deposition

4-(N,N-dimethylamino)-3-acetamidonitrobenzene (DAN) was evaporated onto a glass plate and a cleavage surface of KCl in vacuo. DAN films deposited on the glass plate were composed of randomly oriented laminate crystallites. The DAN film deposited on KCl substrate, on the other hand, was composed of tabular crystallites crossing orthogonally. The (001) plane of the DAN crystal lay parallel to the substrate surface, and its a axis oriented parallel to the 〈110〉 directions of the KCl substrate. The second harmonic (SH) intensities of DAN films were measured. When the film deposited on KCl substrate was rotated around an axis coinciding with the laser beam propagation direction, the SH intensities of the film changed periodically corresponding to the molecular configuration in the film. The biorientational order of DAN crystal observed by electron microscopy on KCl substrate was confirmed on a macroscopic scale by second harmonic generation.