Yanlong Che

Fabrication of Surface Relief Grating with Second-Order Nonlinearity Using Urethane-Urea Copolymer Films

Surface relief gratings on azobenzene-substituted urethane-urea copolymer films with large second-order nonlinearity are fabricated by a laser-interferometric method. The surface relief structures are obtained upon exposure to an interference pattern of a polarized Ar+ laser beam, which mainly results from photoablation. The gratings are thermally stable at temperatures higher than glass transition temperature (Tg) of the copolymer. The surface relief gratings with second-order nonlinearity are fabricated after a corona poling process. We report what we believe to be the first experimental observation of the separated second-harmonic generation from the fundamental wave by the surface relief grating with second-order nonlinearity.

Formation of channel waveguide with grating in polymer films based on simultaneous photobleaching and embossing

Channel waveguide with grating is fabricated in nonlinear optical (NLO) polymer thin films by means of simultaneous embossing and photobleaching. A combined structure of mask/master consisting of a photomask part and a grating die part which is made of polyimide is fabricated. Then the mask/master is set on the NLO polymer films and both embossing and photobleaching are performed simultaneously. Profiles of the replica grating and the channel waveguide are estimated.

Single-pulse ultraviolet laser recording of periodically poled structures in polymer thin films

A simple fabrication technique for nonlinear polymeric optical waveguide patterns is introduced based on the two-beam interference method. We determined that the second-order nonlinearity of poled polymer films is erased by single-pulse ultraviolet (UV) laser irradiation. The erasure mechanism for second-order nonlinearity is discussed. To form a periodic structure in an optical polymer waveguide, two types of optical configuration of two-beam interference were arranged, and a single-pulse UV laser was exposed directly onto poled films. We prove that this method provides a simple way to fabricate volume-type and ridge-type periodically poled structures, i.e., chi(2) gratings, from the submicrometer to the millimeter range.

Stable surface relief grating with second-order nonlinearity on urethane-urea copolymer film

Abstract Surface relief gratings (SRGs) on azobenzene-contained urethane–urea copolymer film with second-order nonlinearity are fabricated by laser-interferometric method. The surface relief structures are obtained upon exposure an interference pattern of a CW Ar+ laser and a single-pulse UV laser. The SRG is thermally stable even at Tg of the copolymer. The mechanism of the stability is investigated by comparing the pulse UV laser inscribed SRG. It is suggested that laser ablation of the copolymer surface by the high-power laser irradiation is taken into account. Second-order nonlinearity is induced by corona-poling process after grating formation. Diffraction of second-harmonic generation (SHG) is observed by inserting a fundamental beam, which is in agreement with vector diagram.

High-resolution periodically poled structure in diazo-dye-substituted polymer film based on direct electron-beam writing technique

A periodically poled pattern in diazo-dye-substituted nonlinear optical polymer film is fabricated by direct electron-beam (EB) writing. It is found that the second-order nonlinearity of corona-poled polymer thin film is erased after EB irradiation. Moreover, the exposed region can be easily removed by conventional wet development. A high-resolution periodically poled structure (i.e., χ(2) grating) with a period of 0.60 μm is demonstrated based on the direct EB writing technique.

Polymeric optical waveguide components fabricated by simultaneous embossing and poling at elevated temperatures

Simple fabrication technique of nonlinear optical waveguide components in polymer films based on simultaneous embossing and poling at elevated temperature (SEPET) is proposed and demonstrated. The master gratings which consist of polyimide die and metal base are fabricated by a single pulse two-beam interference technique using UV laser ablation. The master grating is found to be stable enough against heat and mold treatment cycles. The master molds nonlinear optical polymers at their Tgs. At the same time, high voltage is applied to the polymers to induce second-order nonlinearity. The grating profile as well as the nonlinearity is estimated. Moreover, formation of channel waveguide with grating based on the present process is also discussed.

Two-Way Holographic Image Storage in Photosensitive Polymers

We report two-way holographic image storage in azo polymers. Urethane-urea copolymers involve two photochemical reactions, photoanisotropic modification and surface modification. We can realize the recording of two holograms: (polarization volume hologram due to the anisotropy of azo side chain and surface relief hologram) that have different types of information. This is possible because the polarization volume hologram is rewritable while the surface relief hologram is thermally stable. Using the fact that the polarization volume hologram acts like a half wave plate, we can separately readout the different types of information.

Fabrication of High-Resolution Periodical Structure in Photoresist Polymers Using Laser Interference Technique

Periodical structures in the nanometer order, which are clearer and of superior aspect than those reported elsewhere, were fabricated. These structures were fabricated onto a positive-type photoresist film by a two-beam interference technique using a single-pulse Nd:YAG (355 nm) laser. A grating structure with a depth of more than 300 nm and period of 400 nm was formed, accompanied by wet development. Moreover, a 200-nm-period grating, which is close to the theoretical limit, was successfully fabricated with higher aspect.

Study on Electron Beam Lithography with Dye-Doped Polymer Material

Abstract We report the study on electron-beam(EB) lithography with a dye-doped poled polymer. The mechanism of absorption spectrum change and nonlinear characteristics after EB exposure are investigated. Aχ(2) diffraction grating is successfully fabricated in this guest-host polymer material based on direct EB irradiation technique.

High Resolution Pattern Recording on Photosensitive Urethane-Urea Copolymer Film Surface by Laser Irradiation through Photo-mask

a Shizuoka University, NEDO Technical Fellow, Center for Joint Research, 3-5-1 Johoku, Hamamatsu-shi, Shizuoka, 432-8561, Japan Tel/Fax: +81-53-478-1429 E-mail: myche@ipc.shizuoka.ac.jp b Shizuoka University, Faculty of Engineering, 3-5-1 Johoku, Hamamatsu-shi, Shizuoka, 432-8561, Japan c Toyota Central Research and Development Laboratories Inc., 41-1 Yokomichi, Nagakute-cho, Aichigun, Aichi 480-1192, Japan