Perforated Bimodal Interferometric Biosensor for Affinity Sensing

A compact photonic sensor using a perforated waveguide (PW) that functions as a bimodal interferometer (BiMI) is developed for affinity sensing. A 2D array of holes is formed on the bimodal region of the waveguide. The PW is designed to allow 1.31 mu m wavelength light to transmit, harnessing the strong optical intensity distribution inside the holes to enhance the sensitivity of the sensor. Numerical simulations show that the PW-BiMI outperforms a nonperforated BiMI in surface sensitivity by 7.6 times. A molecularly imprinted polymer for human serum albumin (HSA) is synthesized and coated on the PW-BiMI. The sensitivity and detection limit for HSA achieved using a 100 mu m long sensor are 154 nm mu m(-1) and 20.4 mu g mL(-1), respectively. Compared with a BiMI of equivalent length, the PW-BiMI sensor would have a 22 times larger surface sensitivity, and the detection limit would be decreased to 31%. The PW-BiMI sensor has potential for application in label-free biosensing with a small volume of solution.