Integrating Vernier spectrum with Fano resonance for high sensitivity of an all-optical sensor

Abstract

Vernier and Fano resonances are promising approaches for enhancing the sensitivity of an alloptical sensor. A theoretical analysis was performed to integrate a Fano-like resonance shape with a Vernier resonance by considering the presence of partial reflective end facets at a double microring resonator waveguide. The system was developed based on scattering matrix and optical transfer function. The double and all-pass racetrack microring configurations were compared with and without the end facet at the waveguide to analyze the dynamic change of the output resonance spectrum. The spectrum were analyzed based on the free spectral range and resonance pattern. The resonator systems were applied to refractive index-based sensing protocol, which was operated by a shift of resonance wavelength with a change of refractive index. The sensitivity was optimized by varying the configuration parameters such as the radius of the ring, the distance between end facet, and the coupling coefficients. Integrating Vernier spectrum with Fano resonance improved the sensitivity for all-pass racetrack configuration by 5.16 % and the sensitivity for double racetrack configuration by 6.31 %. The recorded limit of detection (LOD) of double racetrack was 3.30 × 10 -5 .

Enhancing Vernier Effect through Integrated Add-Drop Microresonator for High Sensitivity All-Optical Sensing

“…The simulated add-drop MRR shows consistent pattern compared with the literature finding [47]. Based on Figure 3b, the Fano resonance spectrum was obtained by using the parameters given in [41] and the resonance spectrum generated, pattern-wise, is in good agreement with the previous findings [41], [48]. Therefore, the add-drop MRR and Fano resonance simulation system can be applied to other configurations for further studies.…”

“…Figure 3a shows the simulated resonance spectrum for the add-drop MRR from our simulation system whereas Figure 3b shows the Fano resonance spectrum obtained via all-pass MRR with a pair of partially reflecting air holes incorporated in the bus waveguide. Both simulated resonances have been compared with previous literature finding [41], [47], [48] to validate our system. Based on Figure 3a, the spectrum generated was calculated over a wavelength range of 1.5506 𝜇m to 1.5518 𝜇m.…”

“…The Fabry-Perot resonance is obtained via the air holes that act as reflectors for the propagating resonance in the bus waveguide. Furthermore, the output spectrum of the MRR configuration propagates in a packet pattern due to the Ve rnier effect and it is very useful to distinguish the maximum peak of the resonance [50] especially in sensing applications [48].…”