High-Q guided mode resonance sensors based on shallow sub-wavelength grating structures.

We present a systematic investigation on the enhancement of the quality (Q) factors for guided-mode resonance (GMR) sensors with shallow subwavelength grating structures. By introducing the coupled-mode model, a theoretical high-Q factor can be achieved by choosing the proper geometric structure. Based on this method, a GMR sensor with a Q factor up to 8000, which is an order of magnitude larger than those of typical GMR sensors with Q factors within 100~300, was demonstrated experimentally. Besides, the approached GMR sensor achieved a bulk sensitivity of 135 nm/RIU with a high signal to noise ratio, which supports a detection limit of 1 ng/mL for bovine serum albumin detection.