Masahiro Tomiki

All-fiber Q-switched operation of thulium-doped silica fiber laser by piezoelectric microbending

We demonstrate an all-fiber Q-switched laser operation in the 2 µm region on the basis of a dynamic periodic microbend and pulsed-pump configuration. A single-mode thulium-doped silica fiber is pumped by 1.6 µm-band laser diodes, and the dynamic loss is introduced in the fiber ring resonator by the periodic microbend that is electrically controlled with a piezoelectric actuator. When the voltage-off period of the piezoelectric actuator is set at 20 µs for the pump power of 120 mW, the output pulse power is measured by 420 mW with a pulse width of 1.3 µs.

Loss Tunable Long-Period Fiber Gratings Controlled by Electromagnet

We present microbend long-period fiber gratings that can be used as electrically loss-tunable band-rejection filters. The tunability of wavelength-selective loss is based on variable perturbation of the fiber induced by an electromagnet in combination with a steel coil spring. A dynamic loss amplitude of 11 dB is obtained and the response time measured is 16-18 ms.

All-fiber Tunable Q-switched Tm Fiber Lasers for Greenhouse Gas Sensing

Q-switching and tuning operations of Tm-doped fiber lasers are demonstrated by employing dynamic fiber microbend. Pulse peak power of 1.45 W and tunable range of 100 nm are obtained around 1.9 μm with 100 mW-class pump laser diode.

Fabrication method of large-core polymeric optical waveguide through replication process using anisotropically etched silicon

Fabrication method of large core polymeric optical waveguides by three-time replication of anisotropically etched (110) single-crystal silicon original molds is proposed. Those replication processes consist of soft lithography, UV embossing and hot embossing. Original masters for this replication process were fabricated by anisotropic etching of (110) single-crystal silicon wafers by a strong alkali solution. The optimum conditions of anisotrophic etching are etching temperature of 60° C and the alkali solution concentration of less than 30wt%. Original masters replicated to silicone rubber molds by soft lithography. Then, using UV embossing, the silicone rubber molds replicated to an UV-curable resin for hot embossing stampers. The stampers by hot embossing replicated to rectangular groove PMMA replicas that act as undercladdings for optical waveguides. The optimum conditions of hot embossing are the heated temperature of over 130° C, the pressure of more than 50kgf and the removal temperature of less than 110° C. In this work, channel optical waveguides with 100, 300, 500 μm core size were fabricated by controlling the pattern width of silicon and etching time of silicon. Low Propagation losses of 0.30, 0.22 and 0.19dB/cm at 650nm were realized for 100, 300, and 500 μm core waveguides, respectively.

Heat-Resistant Polyarylates for Waveguide-Type Device Application

Polyarylates (PARs) with high glass transition temperature (Tg) of over 200°C are newly synthesized and used for waveguide-type device application. Thermal and optical properties of PARs are investigated, and results indicate that PARs show high thermal stability as well as high optical transparency in the visible region. High-resolution relief gratings on PAR thin films are fabricated by a direct electron-beam (EB) writing technique together with thermal development. Using a reactive-ion-etching (RIE) technique, the waveguide channel ridge was fabricated.

Pulsed operation of Tm-doped fiber lasers using piezoelectric-driven microbend applied to elliptical coating fibers

We report Q-switched pulse generation in Tm-doped fiber lasers by introducing piezoelectric-driven microbend into an elliptical coating fiber in a fiber ring resonator. Compared with the untreated circular fiber having a diameter of 240 μm, the elliptical coating fiber was flattened to have a major axis diameter of about 300 μm. We employed a pair of comblike plates attached on the piezoelectric actuators in order to bend the fiber from both sides. The output pulse power is improved by optimizing the tooth-width and spatial period of the comb-like plates, so that the elliptical coating fiber is easily bent and the propagation mode is efficiently coupled to radiation modes around λ = 1.9 μm. The Tm-doped fiber is pumped by a laser diode emitting at 1.63 μm and the pump light is introduced to the fiber ring resonator via the wavelength division multiplexing coupler. The emission spectra showed that the center oscillation wavelength was typically 1.92 μm. When the pump power was increased to 156 mW, the output pulse showed a peak power of 42.5 W with a pulse width of 1.06 μs. We expect that the in-fiber Q-switching technique will provide simple laser systems for environmental sensing and medical applications.

Light-induced self-written polymeric waveguides for low-cost integration of single-mode devices

We demonstrate the feasibility of optical interconnection waveguides, including a Bragg grating and EO waveguides, formed by a self-trapping effect into a novel photopolymer. These technologies are useful for the integration of chip-scale photonic devices.

High durable mold fabricated with hot-embossing a sol-gel derived organically modified silicate film

A high durable and low-cost mold was fabricated with hot-embossing a sol-gel derived organically modified silicate film using a commercially available grating as a mother mold. Close pattern transfer from the mother mold to the film (daughter mold) was confirmed. The thermooptic coefficient of the daughter mold was measured and found to be unchanged during 9 times heating and cooling cycle. This result implies that the mold has no residual stress and so leads to fine patterning in embossing process. We hot-embossed polymethyl methacrylate (PMMA) films not with the expensive mother mold, but with the daughter mold. More than thirty PMMA grating replicas could be successively fabricated using one daughter mold without cleaning and treating the surface. This is due to the hydrophobicity of the daughter mold. After heating at 250°C for 120 hours, the water contact angle was approximately above 90°, and so the daughter mold did not lose its hydrophobicity. Because of the hydrophobicity, no significant problem that the daughter mold stuck to the PMMA film was observed for the successive embossing. It was confirmed with AFM observation that there was no difference in pattern dimension between the daughter mold and PMMA replicas. Hence, the daughter mold is high durable. Moreover, we measured the transmitted diffraction light power of the fabricated PMMA gratings, and found that there was no difference in the diffraction efficiency of the gratings. Therefore, the daughter mold is suitable for low-cost hot embossing of polymer materials.

Electron-Beam Lithography and Thermal Development to Fluorinated Polyarylate

1 Shizuoka Univ., Dept. of Electrical and Electronic Eng. 3-5-1 Johoku, Hamamatsu, Shizuoka 432-8561, Japan Phone: +81-53-476-1094 E-mail: tmtomik@ipc.shizuoka.ac.jp 2 Shizuoka Univ., Dept. of Electrical and Electronic Eng. 3-5-1 Johoku, Hamamatsu, Shizuoka 432-8561, Japan 3 Tohoku Univ., Institute of Multidisciplinary Research for Advanced Materials, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan

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