Low-loss LSRPP waveguides could lead to inexpensive integrated optical devices

For a sufficiently thin metal stripe embedded in a dielectric material, light coupled into the stripe becomes a long-range surface-plasmon polariton (LRSPP); the simplicity and ease of fabrication of such a LRSPP waveguide has potential for extremely low-cost integrated optical communications. But LRSPP waveguides typically have relatively high optical loss. Now, scientists at the Electronics and Telecommunications Research Institute and KAIST (both in Daejeon, Korea) and SungKyunKwan University (Suwon, Korea) have created LSRPP waveguides with transmission losses of as low as 0.4 dB/cm. (This is the same group who previously reported creating bendable LSRPP waveguides; see www.laserfocusworld.com/articles/352159.)

The 11-nm-thick waveguide was buried in a UV-curable fluorinated polymer with a loss of 0.1 dB/cm and refractive index of 1.451 at the 1.31 µm experimental wavelength. The researchers tested stripe widths ranging from 1.5 to 10 µm. The 0.4 dB/cm loss was recorded for a stripe width of 2.0 µm; for a width of 4.5 µm, they measured a coupling loss into and out of a polarization-maintaining single-mode fiber of 1.0 dB. The results can be further improved by using a surrounding dielectric with a lower refractive index and lower loss, say the researchers. Contact Suntak Park at [email protected].