Photonic Systems Brown Bag Seminar Series

Thursday, March 9, 2006, at 12 noon           RLE Haus  Conf. Rm 36-428

Ultrawide tuning of photonic microcavities via evanescent field perturbation

Peter Rakich 

The field of integrated optics promises to provide a practical and scaleable means of routing and switching light for numerous applications ranging from telecommunications networks to sensing and spectroscopy. However, there are currently few practical means of creating large changes in waveguide effective index in microphotonics, forming a key barrier to the development of dynamic integrated optical circuits. A large change in effective index is critical for the development of widely tunable filters and for scaling active components to smaller size. Currently, thermo-optical tuning is the only widely implemented means of producing changes in effective index in integrated circuits, but it has insufficient range, and is slower than desired for many applications.  For this reason we explore geometrical tuning mechanisms, such as evanescent tuning of microphotonic circuits. 

In the follwing study Evanescent field perturbation of an integrated microring resonator is examined as a means of achieving high-fidelity reversible tuning of photonic microcavities over large wavelength ranges. A 1.7% wavelength tuning is achieved through the use of a novel silica fiber probe that provides access to the evanescent field of an air-clad high-index-contrast ring resonator. As the microring is perturbed, the probe–ring distance is found through simultaneous nanometric distance calibration and force measurements. Experimental results agree well with theoretical tuning. Some challenges of microelectromechanical systems implementation of this effect is discussed, as well as avenues for improvement of the tuning range.