Sub-dB/cm propagation loss in silver stripe waveguides.

We demonstrate sub-dB/cm propagation losses in polymer-based silver stripe waveguides at the wavelength of 1.31 microm. The silver stripe waveguides were fabricated in a low-loss fluorinated polymer clad. To form uniform metal stripe patterns, which are essential for reducing propagation loss, we developed a lift-off process using double layers of photoresist and SiNx. A propagation loss of less than 1.0 dB/cm was obtained with the 11- nm-thick silver stripes in the width range of 1.5 - 4.5 microm. A coupling loss of approximately 1.0 dB with a polarization maintaining single mode fiber was achieved for a width of 4.5 microm. For a width of 2.0 microm, we recorded a minimum propagation loss of 0.4 dB/cm, which is comparable with that of dielectric multi-mode waveguides.