Integrated power monitor for long-range surface plasmon polaritons

We propose a method for monitoring the power carried by long-range surface plasmon polaritons (LRSPPs) propagating along a metal stripe embedded in dielectric. The method utilizes the fact that the stripe is heated by LRSPPs (due to ohmic loss), and is based on stripe resistance measurements using a Wheatstone bridge configuration. 1-mm long power monitors integrated with LRSPP guides, consisting of 15-nm thin and 8-μm wide gold stripes embedded in polymer, are fabricated and characterized at telecom wavelengths, featuring linear responses for up to 50 mW of input power, responsitivities of up to 0.15 mV/mW (for a bias voltage of 2 V), weak wavelength dependence and total (fibre-to-fibre) insertion losses down to 2 dB when using single-mode and polarization-maintaining fibres.