Kazunori Mune

Self-written waveguide structure in photosensitive polyimide resin fabricated by exposure and thermosetting process

A new fabrication technique of self-written waveguide was developed by using a photosensitive polyimide (PSPI) resin. The PSPI resin enables us to fabricate a solidified cladding portion of the self-written waveguide only by a thermosetting process after writing of the waveguide core. In the PSPI resin, a self-focusing effect of the exposing laser light, induced by difference in refractive index between exposed and unexposed portions, was observed. The coupling loss between two multimode fibers, which were placed with 0.5-mm gap, was decreased to 0.7 dB by insertion of the PSPI all-solid self-written waveguide. This simple fabrication method of the self-written waveguide structure is applicable to a convenient alignment technique of optical components.

Propagation-mode-controlled fabrication of self-written waveguide in photosensitive polyimide for single-mode operation

We have developed a new fabrication method of single-mode self-written waveguide by controlling the propagation mode in an optical fiber. This method is very appropriate for repeatable fabrication of the single-mode self-written waveguide. Since a Gaussian-like near-field pattern is required for the fabrication of a tiny and uniform waveguide core, the propagation mode in a conventional optical communication fiber was controlled by coupling with an optical fiber having 3-/spl mu/m core, which shows a single-mode operation at visible wavelength region. Single-mode propagation at optical communication wavelength was confirmed for the fabricated self-written waveguide. The evaluated core diameter of the self-written waveguide was /spl sim/9.5 /spl mu/m.

Fabrication of self-written waveguide in photosensitive polyimide resin by controlling photochemical reaction of photosensitizer

We have investigated optical properties of photosensitive polyimide appropriating for long self-written waveguide fabrication. From systematic measurements of absorption properties, it was found that photochemical reaction of photosensitizer dissolved in the photosensitive polyimide resins relates to transparency after the exposure, which limits the length of the fabricated self-written waveguide. By controlling the photochemical reaction, in which the photosensitive polyimide resin has sufficient transparency during exposure, four times longer self-written waveguide core was fabricated.

Fabrication of low-loss optical waveguides using a novel photosensitive polyimide

Fabrication of optical waveguides by a simple patterning process using photosensitive polyimide (PSPI) is described. Light waveguide based on PSPI was fabricated by photolithographic processing without use of dry etching process. The PSPI varnish is comprised of polyamic acid (PAA) which was made from fluorinated diamine and fluorinated tetracarboxylic dianhydride, and photosensitizer. The PSPI has the following characteristics: glass transition temperature (Tg) of 330 °C, coefficient of thermal expansion of 40 ppm/K. Moreover the PSPI is colorless, and posses low absorption at 1 .3 and 1 .55im. The sidewalls and the surfaces ofthe fabricated waveguide are very smooth, which is essential for the low loss optical mode propagation and lower scattering of the mode due to the imperfections. Single and multimode buried ridge waveguides on quartz glass substrate were fabricated and tested. Optical propagation losses were measured by standard cut back method and found to be as low as 0.4 dB/cm @ 1.55 jim. This fabrication process would be expected to contribute to low cost production for high performance opto-electronic devices.

New waveguide technique using photosensitive polyimide for integrated optics

New fabrication methods of optical waveguide and light-induced self-written waveguide were developed by using photosensitive polyimide resin. This resin will enable to reduce cost of optical devices and modules by a simpler fabrication process.