Photonic Systems Brown Bag Seminar Series

Thursday, March 23, 2006, at 12 noon           RLE Haus  Conf. room 36-428

Critically Coupled Resonators in Vertical Geometry Using a Planar Mirror and a 5 nm Thick Absorbing Film

Yaakov Tischler

We report the linear optical properties of a critically coupled resonator (CCR), a thin film structure that can absorb nearly all of the incident light of a given wavelength in a few nanometer thick absorbing film. The CCR consists of a dielectric Bragg reflector (DBR) as the mirror, a (5.1 ± 0.5) nm thick film of J-aggregated cyanine dye as the absorbing layer, and a spacer layer of transparent material that separates the mirror and absorber layer by the correct distance needed for critical coupling. More than 97% of the incident l c = 584 nm wavelength light is absorbed within the (5.1 ± 0.5) nm thick absorber layer, corresponding to a peak effective absorption coefficient of a eff = (6.9 ± 0.7) x10 6 cm -1 . Critical coupling is shown to be achievable with a variety of material sets, providing several general conditions are satisfied. Among non-epitaxially grown materials, we can envision building CCR's with organic polymers that are used in biological assays and chemical sensors, with molecular materials that are used in photodetectors and xerographic photoresistors, and in the emerging uses of colloidally grown inorganic nanocrystal quantum dots (QDs). Application of the CCR phenomenon can also facilitate development of single photon optics where it is desirable to absorb a photon with 100% probability in the thinnest possible films and colloidally grown semiconductor saturable absorber mirrors (SESAMS) for ultra-fast optical modulators. Finally, the connection is made between the CCR phenomenon and recently demonstrated microcavity structures that exhibit strong coupling of light and matter in the form of exciton-polariton resonances to assist in the development of future devices that operate in the strong coupling regime.