Sensitivity enhancement of differential splitter-based transduction for photonic microcantilever arrays.

We report enhanced sensitivity for in-plane photonic transduction of static deflection of microscale cantilevers by modifying the mode structure of double-step rib waveguides used to capture light from the free end of waveguide microcantilevers. A measured sensitivity of 0.77 x 10( - 3) nm( - 1) is achieved, comparable to the best reported for the optical lever method and over two orders of magnitude larger than for piezoresistive transduction. The corresponding minimum detectable deflection is 59 pm for a 3.5 Hz measurement bandwidth.