Enhancement of refractive index sensitivity of Bragg-gratings based optical waveguide sensors using a metal under-cladding

Highly Sensitive Refractive Index Sensor Based on Polymer Bragg Grating: A Case Study on Extracellular Vesicles Detection

“…It is worth noting that, unlike the germanosilicate core in Ref. [ 30 ], here we have considered PMMA as the waveguide core since it shows a good adhesion with the metal layer. Further, PMMA can directly act as the resist as well as waveguide core, which makes it easy to form the ridge waveguide using deep UV lithography or e-beam lithography, which has been reported with well-known dielectric-loaded surface Plasmon polariton (DLSPP) waveguide geometry [ 32 ].…”

“…The high interacting field leads to a high sensitivity. Over the years, various photonic structures have been proposed such as surface Plasmon polaritons (SPPs) [ 17 , 18 ], 2D materials [ 19 , 20 ], long period gratings (LPGs) [ 21 , 22 ], multimode interferences [ 23 ], ring resonators [ 24 , 25 ], Bragg gratings [ 26 , 27 , 28 , 29 , 30 , 31 ], etc. The performance of the structures based on LPGs, SPPs, multimode interferometers, and ring resonators is often limited by broad bandwidth, a bulky setup, or a free spectral range.…”

“…Following this structure, a high sensitivity of 507 nm/RIU has been reported recently [ 29 ]; however, the requirement of a double periodicity (SWG and Bragg grating) and the periodical loading of blocks to form the gratings also brings complexity in device geometry. Earlier we have reported a Bragg grating-based sensor with metal under cladding in simple ridge waveguide geometry [ 30 ]. It has been observed that the metal under cladding can significantly enhance the evanescent field in the sensing medium for the non-plasmonic mode and yields a sensitivity of 237–578 nm/RIU for an RI range of 1.3–1.4, suitable for bio-sensing.…”

Optimization of Ridge Waveguide Structure for Temperature Sensor Application Using Finite Difference Method

“…Compared to optical fiber, optical waveguide has some advantages such as robust, has high sensitivity, easy light intensity measurement and can be realized in onchip sensor [4]. Various optical waveguide sensors have been proposed for various applications such as for refractive index measurement [5][6][7], and biosensor [8,9]. The published waveguide-based optical sensor were proposed by implementing various method such as surface plasmon resonance [4,10,11], Bragg grating [7] and mode coupling [6].…”

“…Various optical waveguide sensors have been proposed for various applications such as for refractive index measurement [5][6][7], and biosensor [8,9]. The published waveguide-based optical sensor were proposed by implementing various method such as surface plasmon resonance [4,10,11], Bragg grating [7] and mode coupling [6]. For temperature measurement, waveguide-based optical sensor has been proposed using intensity modulation method by applying curved waveguide [12].…”