Sensitivity of triangular resonator with long evanescent field around critical angle

Abstract

A novel triangular resonator with a long evanescent field around the critical angle has been analysed and demonstrated for the first time. The sensitivity of the resonance shift used for changing the refractive index of 1 × 10 25 at the incidence angle of 188 is 1.04 × 10 27 nm/ RIU for transverse magnetic polarised light. An extinction ratio of 6 dB was observed near 1550 nm, where the incidence angle of the total internal reflection mirror inside the resonator was 188.Introduction: Microring resonators are very desirable for photonic applications owing to their compact features and manifold functionality [1]. Owing to very high Q-factor resonances and steep slopes, photonic microring resonators have begun to be employed in biological and chemical sensing [2]. Triangular resonators, also known as ring resonators, can provide an attractive solution for such functions [3]. Very compact cavities can be achieved by combining the total internal reflection (TIR) mirrors with regular waveguides. One of the TIR mirrors can then be used for the sensing region because of the Goos-Hänchen (GH) effect in the TIR mirror having a sharp incident angle. The TIR mirror having a sharp incident angle increases the evanescent field owing to the GH shift. Because of this, long evanescent fields can be employed to measure the quantities happening in biological events. In this Letter, we propose and investigate a novel triangular ring resonator incorporating a TIR mirror with a long evanescent field to achieve compactness and high sensitivity.

A novel biosensor design using a triangular resonator

“…We fabricated one such resonator integrated with a multimodeinterference (MMI) coupler, tapers, TIR mirrors, and semiconductor optical amplifiers (SOAs). 4,5 The ridge waveguide of the ring resonator, which has a width of 3 m, contains active material that forms the SOA. The input and output waveguides are connected through short 15 m-long tapers with linearly decreasing widths.…”

“…This phase shift is dependent on external variables, allowing it to be used as a sensing indicator. The sharp incident angle at the TIR mirror also increases the evanescent field due to the GH shift, 4,6 which can also increase the optical coupling efficiency of the PIC system so that it can be used as an effective sensing device for quantitative monitoring of biological events.…”