Dynamic tuning of optical waveguides with electrowetting pumps

This paper reviews some of our recent work on a new class of photonic component that uses electrowetting pumps and microfluidic channels for dynamic tuning of the characteristics of optical waveguides. These pumps exploit the ability to alter the contact angle of conductive liquids situated on top of a dielectric layer with appropriately patterned underlying electrodes. By applying different voltages to opposite sides of a conductive fluid plug, the contact angle imbalance created between the ends of the liquid drives fluid motion toward the higher field regions [1]. In our design, this electrically controlled, fully reversible motion of fluids contained within recirculating channels is used to alter the effective indices of waveguide modes of three different types of optical fiber structures: fiber Bragg and long period gratings and etched or tapered fiber. Our systems operate non-mechanically and have excellent optical performance, including low insertion and polarization-dependent losses. These characteristics suggest a promising potential for electrowetting-based microfluidic tuning of optical fiber devices and other photonic components.