We report the first observation of Fano resonance in the Y-shaped cavity (YC), demonstrate that the sensitivity of the sensor is as high as 1160 nm/RIU, much higher than that of the aforementioned sensors, and observe that the quality factor and sensitivity of Fano resonance can be adjusted by changing the geometry of the sensor or adding silver nanoparticles. Traditional sucrose detection methods either waste resources or pollute the environment. This work shows that the sensor can be used to detect the concentration of sucrose. In addition, we found that the concentration of sucrose has a linear relationship with its corresponding refractive index. The sensor we designed can easily and rapidly calculate the concentration of a sucrose solution based on the Fano resonance wavelength shift, which is an important first step towards detecting the refractive index of the solution and identify the composition.

At present, an important research area is the search for materials that are compatible with CMOS technology and achieve a satisfactory response rate and modulation efficiency. A strong local field of graphene surface plasmon polariton (SPP) can increase the interaction between light and graphene, reduce device size, and facilitate the integration of materials with CMOS. In this study, we design a new modulator of SPP-based cycle branch graphene waveguide. The structure comprises a primary waveguide of graphene–LiNbO3–graphene, and a secondary cycle branch waveguide is etched on the surface of LiNbO3. Part of the incident light in the primary waveguide enters the secondary waveguide, thus leading to a phase difference with the primary waveguide as reflected at the end of the branch and interaction coupling to enhance output light intensity. Through feature analysis, we discover that the area of the secondary waveguide shows significant localized fields and SPPs. Moreover, the cycle branch graphene waveguide can realize gain compensation, reduce transmission loss, and increase transmission distance. Numerical simulations show that the minimum effective mode field area is about 0.0130l2, the gain coefficient is about 700 cm–1, and the quality factor can reach 150. The structure can realize the mode field limits of deep subwavelength and achieve a good comprehensive performance.