Micron-scale tunability in photonic devices using microfluidics

Optofluidics offers new functionalities that can be useful for a large range of applications. What microfluidics can bring to microphotonics is the ability to tune and reconfigure ultra-compact optical devices. This flexibility is essentially provided by three characteristics of fluids that are scalable at the micron-scale: fluid mobility, large ranges of index modulation, and adaptable interfaces. Several examples of optofluidic devices are presented to illustrate the achievement of new functionalities onto (semi)planar and compact platforms. First, we report an ultra-compact and tunable interferometer that exploits a sharp and mobile air/water interface. We describe then a novel class of optically controlled switches and routers that rely on the actuation of optically trapped lens microspheres within fluid environment. A tunable optical switch device can alternatively be built from a transversely probed photonic crystal fiber infused with mobile fluids. The last reported optofluidic device relies on strong fluid/ light interaction to produce either a sensitive index sensor or a tunable optical filter. The common feature of these various devices is their significant flexibility. Higher degrees of functionality could be achieved in the future with fully integrated optofluidic platforms that associate complex microfluidic delivery and mixing schemes with microphotonic devices.