Long-range surface-plasmon polaritons (LRSPPs), which are electron disturbances at a metal surface resulting from interactions with light, may become a practical way to transmit optical information in commercial devices such as mobile phones. Researchers at the Electronics and Telecommunications Research Institute and KAIST (both in Daejeon, Korea) and SungKyunKwan University (Suwon, Korea) have created a flexible plasmon waveguide consisting of an 8-nm-thick, 68-mm-long silver strip embedded in a multilayer, low-loss polymer film. The vertical bending loss is less than 0.3 dB/180° at 1310 nm for a 2 mm bending radius and a 180°.
A previous version with only a single layer of polymer cladding lost significant optical power at bending radii of 20 mm; the new version uses a 10-µm-thick inner cladding with a refractive index of 1.524, along with a pair of lower-index (1.514) 20-µm-thick outer claddings. Tests were conducted both by coupling a multimode fiber with a 50-µm-diameter core and a single-mode fiber to the output of the LRSPP waveguide. Because the researchers found no periodic output changes as bending was increased, they believe that the LRSPP mode doesn’t lose energy to the dielectric waveguide mode; however, further study is required to determine this. Contact Suntak Park at [email protected].