All-optically triggerable organic/inorganic photonic devices

Abstract

Optical resonant cavities form the foundation for a wide range of integrated optical components. While a high performance laser requires a high quality factor (Q) cavity, other types of devices, like modulators, rely on the cavity resonant wavelength being tunable. Numerous mechanisms based on the thermo-optic and electro-optic effects have been leveraged to create switchable or tunable devices; however, these are very power hungry and/or require complex control machinery. In the present work, we graft an air-stable, optically triggerable functional group to the surface of an ultra-high-Q optical cavity. The Aazobenzene functional group switches from trans to cis upon exposure to blue light, and it can be thermally triggered to revert to the initial trans state. Using a single tapered optical fiber waveguide, blue and near-IR light can be coupled into the device simultaneously. When the blue light interacts with the Aazo group, the resonant wavelength blue shifts. Upon exposure to a CO2 laser, the resonant wavelength returns to its initial position. Several different aspects of the device operation were investigated, including the kinetics of the switching, the effect of switching via a resonant or non-resonant optical field, and sterics of the switching. Notably, by tuning the surface density of the Aazo groups using a multi-material surface chemistry, it is possible to control the magnitude of the shift.