Oscillating wave sensors based on ultrahigh-order modes in symmetric metal-clad optical waveguides

An oscillating wave sensor that uses ultrahigh-order modes in symmetric metal-clad waveguide with submillimeter scale is investigated to measure minute changes in refractive index (RI) of aqueous solution. In the proposed sensor, the sample acts as the guiding layer where oscillating wave propagates. Owing to the concentrated power in the sensing region and the use of the very sensitive ultrahigh-order modes, it is demonstrated both theoretically and experimentally that its sensitivity is enhanced by one order of magnitude than that of evanescent wave sensor. The sensor also provides a wide detection range of RI from 1 to 2.0 or higher.