Polymeric variable optical attenuator based on surface plasmon polariton

We propose a polymeric variable optical attenuator based on long range surface plasmon polaritons (LRSPPs) along a thin metal stripe embedded in polymers. The device is operated by controlling radiation loss of the LRSPP mode resulting from the temperature gradient of the polymer cladding caused by a heater. For guiding LRSPPs and efficient coupling of single mode fibers, gold stripes with 20-mu m thickness, 4-W width and 1-cm length are utilized. To obtain long physical lifetime, the heater is formed on the top of the polymer cladding with a 200-nm Au film which is about ten times thicker than the thin metal waveguide. The fabricated device is characterized at a wavelength of 1.55 mu m, exhibiting high attenuation of less than 30 dB with the operating power of 100 mW. The fiber-to-fiber total insertion loss of 6.1 dB is achieved when using single mode fibers.