Silicon nitride based guided mode resonance structures for enhancement of nonlinear optical effects

摘要

Dielectric nanostructures designed in sub-wavelength scale can be tuned to achieve high-Q resonances in the wavelength region of interest with a high concentration of field in and around the structure, which can be used to achieve enhanced light-matter interaction. Such dielectric metasurfaces are potentially conducive platforms for exploiting nonlinear photonic devices at lower input power levels. In this work, we design, fabricate and experimentally demonstrate one-dimensional silicon nitride based guided-mode resonant structure, which exhibits inherently low nonlinear optical effects for enhancing third harmonic signals from a conformal layer of ultra-thin amorphous silicon coated over the gratings. The GMR structures studied here consist of an etched silicon dioxide layer deposited on top of a glass substrate, followed by the deposition of a silicon nitride layer. The thickness of the silicon nitride layer is chosen (~ 160 nm) to achieve GMR resonances around 1550 nm wavelength. The resonance is found to redshift to 1580 nm in presence of the 10 nm amorphous silicon layer. THG studies on the above amorphous-silicon deposited GMR structures shows resonant enhancement of ~ 18x on-grating when compared to off-grating at the peak of the GMR resonance. The present work demonstrates the use of a silicon-processing compatible material stack to realize separately GMR resonances and nonlinear medium to achieve resonant nonlinear enhancement, thus paving the way for silicon-compatible layered nonlinear metasurfaces.