Alternating stacks of metal and dielectric films with nano-hole arrays, called fishnet structures, control the propagation
of electromagnetic waves. In such a structure, changing a dimension or a shape, especially the change in shape of nanoholes,
affect propagation constants. In this study, we report the dispersivity of fishnet structures is controllable with
different hole shapes, by measuring the interferometric fringe in various wavelengths. Two structures were fabricated,
which consist of five alternating stacks of aluminum and silicon dioxide with nano-hole arrays. The holes in one of the
structures are circular with diameters of 500nm, and the other are square with 500nm sides. The lattice constant in each
case is 1,000nm. Since fishnet structures are wavelength-dependent structures, the variable-wavelength interferometric
microscope was set up. The phase shift of the circular hole and the square hole fishnet were about 110 degrees and 85
degrees, respectively, within a tunable wavelength from 1,470nm to 1,545nm. These values were equivalent to a
refractive-index-change of 0.8 and 0.6, respectively. From these results, fishnet structures indicate high dispersivity
within target wavelengths. The dispersion of fishnet structure can be controlled by the shape of the hole.
We developed a novel waveguide fabrication technology, i.e., femtosecond (fs) pulse laser assisted self-writing
waveguide technology, to overcome problems of standard technologies, such as time consuming and high cost. Based on
a light induced self-written (LISW) waveguide fabrication technology, a 488nm cw laser was launched through an
optical fiber into UV curable resin. At the same time a 800nm fs laser was additionally used as a 3D position selective
assistant beam. As the UV resin was cured by the 488nm laser and 800nm fs laser irradiation, a fiber/waveguide
connecting 2D/3D waveguide was easily fabricated.
Plastic optical fibers (POFs) are beginning to replace electrical wiring in many automotive and home applications. In view of this, we have reported the inexpensive wavelength-division-multiplexing (WDM) device for POF system using the LISW waveguide. The LISW waveguides are an attractive and a low-cost process for realizing self alignment between a POF and a waveguide. In this study, we have investigated about the method for precisely aligned LISW polymeric optical waveguides by using an "optical solder" effect. The "optical solder" effect makes it possible to realize a waveguide connection between two faced optical fibers by radiating from both sides even if a significant gap and a small degree of misalignment exist. When we utilize POFs with core diameters of 700μm, waveguides are combinable on the condition that an offset is 700μm or less and a gap is from 6mm to 13mm. By applying this effect, we fabricated precisely positioned LISW waveguides for optical devices. The fiber ends were set at certain mounting positions with respect to the LEDs and PDs. And we evaluated the positioning accuracy. The resulting positional accuracy at the extremities of the optical waveguides is less than one-tenth of the optical fiber core diameter. This value is sufficiently accurate to realize passive alignment. And this result creates new possibilities for boosting the yield of optical modules in mass-production.