Performance of Bragg grating ring resonator as high sensitivity refractive index sensor

In this paper we analyze the performance of a refractive index sensor based on resonant optical structures obtained by closing on itself waveguide Bragg gratings. In particular, a waveguide Bragg serpentine (BSRR), which behaves like a Bragg grating, is proposed. This device shows a spectral response characterized by a photonic band gap (PBG) behavior. Very close to the band gap edges, it exhibits split resonant modes coupled by the grating effect and having a splitting magnitude equal to the PBG spectral extension. By changing the effective refractive index, the photonic band gap splitting magnitude varies. Otherwise, the PBG extension still remains almost unvaried if the length of the device changes, because only the Bragg wavelength will shift. By exploiting this physical principle, these devices can be proved as high sensitivity refractive index photonic sensors, based on a sensing mechanism almost immune to the length variations generated from any environmental perturbation.