High sensitivity and integration nanobeam cavities for the bio-sensing application at 1310 nm

The optical sensor around 1310 nm is an important choice in the next generation photonic integration application. However, the application is hardly developed with a low-index-mode photonic crystal nanobeam cavity (PhCNC). A high sensitivity and integration one dimensional low-index-mode PhCNC is proposed, which consists of a host waveguide and elliptical-shaped holes. To confine the light into the low-index region of the cavity, the width of the host waveguide is decreased quadratically from the center to two sides in the tapered region. Through three dimensional finite-difference time-domain simulation, the TE-like electric field is strongly located in the elliptical-shaped holes, achieving high quality factor and sensitivity. The simulation results indicate that the highest quality factor is about 8 × 105. To demonstrate the performance, the proposed structure is fabricated and measured. The experimental results indicate that a high sensitivity of 390.4 ± 4.2 nm/RIU is achieved, thus showing a potency for on-chip bio-sensing with respect to high sensitivity and small footprints in environment monitoring.