Ultrawide-range refractive-index sensor based on asymmetric integrated Y-junction optical waveguide

We present a novel ultrawide-range refractive index (RI) sensor based on an asymmetric Y-junction optical splitter. A cylindrically shaped rod with a diameter of 350 nm and a height of 1000 nm with a different RI is inserted into a junction of the asymmetric Y-junction waveguide. This rod serves as a sensing area. Our sensor is simulated using a finite-difference time-domain technique. The splitting ratio is studied for the cases of two operating wavelengths, 1480 and 1550 nm. The results show that the splitting ratio can be described as a parabolic function of the RI of the sensing area at both operating wavelengths. An approximately linear relationship between the splitting ratio and the RI occurs in a narrower RI region of 1.00–1.50, thus enabling to design an ultrawide-range RI sensor. The sensor sensitivities at the wavelengths 1480 and 1550 nm are equal respectively to 0.2653 and –0.4908 RIU^–1, with the corresponding R² parameters amounting to 0.9889 and 0.9777. Our device can serve as an ultrawide-range optical RI sensor for identification of micro-scale biochemical or chemical specimens.