Page 322 - Introduction to Information Optics

6.2. Polymer Waveguides

Fig, 6.4. Photograph of compression-molded 3D tapered polymeric waveguides.

layer thickness (7"i) of 2 /mi. Another excellent example of waveguides
fabricated by compression-molding technique is an array of 3-D tapered wave-
guides with large-end cross section of 100/im x 100/.on, and small-end cross
section of 5 /tm x 5 /(m, as shown in Fig. 6.4.
A small section of the molded polymer waveguide is shown in Fig. 6.5, where
the 3D tapering is clearly indicated. The waveguide thus fabricated demon-
strated multiple modes without a cover cladding. However, it exhibits single
mode operation at the small end if a polymeric cladding layer is further
spin-coated on it. Such tapered waveguides have been proposed to bridge the
mode mismatch between two optoelectronic devices having different shapes
and sizes. The one drawback of the compression molding technique is the
initial cost of fabrication of the mold plunger. However, for large production
quantities it may turn out to be most cost effective as the same plunger can be
used again and again.

Fig. 6.5. Photo of a small section of the molded 3D linear tapered waveguide. The cross sections
of the two ends are also shown in the figure.