Refractometric fiber optic sensors have a number of applications in industry due to advantages like remote sensing ability, compact size, easy to fit, etc. A refractometric sensor contains a pair of parallel fibers an...Refractometric fiber optic sensors have a number of applications in industry due to advantages like remote sensing ability, compact size, easy to fit, etc. A refractometric sensor contains a pair of parallel fibers and a gap between the sensor probe and reflector, wherein the liquid whose refractive index is to be measured is filled. This paper describes the importance of mathematical modeling of this sensor. Ray tracing approach is used to model the sensor mathematically. This mathematical model is generalized for any scenario which is useful to avoid tedious trial and error techniques to design the sensor prototype. Mathematical modelling is a useful tool to optimize the gap distance for a detection of refractive index of liquid. The model is developed and analyzed rigorously considering adulteration of diesel by kerosene where refractive index varies from 1.44 to 1.46. Simulation experiments are carried out to optimize the gap distance which is found to be 6.8 mm using both models. Experiments are carried out where sensor probe is fabricated and results are analyzed. It is observed that for suggested gap distance sensor output varies almost linear over the entire range.展开更多
The practical development of compact modern nanophotonic devices relies on the availability of fast and low-cost fabrication techniques applicable to a wide variety of materials and designs.We have engraved a split gr...The practical development of compact modern nanophotonic devices relies on the availability of fast and low-cost fabrication techniques applicable to a wide variety of materials and designs.We have engraved a split grating geometry on stainless steel using femtosecond laser processing.This structure serves as a template to fabricate efficient plasmonic sensors,where a thick gold layer is grown conformally on it.The scanning electron microscope(SEM)images confirm the generation of the split laser-induced periodic spatial structures.The optical reflectance of our sensors shows two dips corresponding to the excitation of surface plasmon resonances(SPRs)at two different wavelengths.Furthermore,the asymmetric shape of these spectral responses reveals a strong and narrow Fano resonance.Our computational electromagnetism models accurately reproduce the reflectivity of the fabricated structure.The spectral responses of both the simulated and fabricated structures are fitted to the Fano model that coherently combines the narrow SPRs with the broad continuum background caused by diffraction.The parameters extracted from the fitting,such as the resonance wavelengths and line widths,are used to evaluate the performance of our device as a refractometric sensor for liquids.The maximum sensitivity and figure of merit are 880 nm/RIU and 80 RIU-1,respectively.Besides the compact design of our sensing device,its performance exceeds the theoretical maximum sensitivity of a classical Kretschmann setup.展开更多
Large-area deep-silver-nanowell arrays （d-AgNWAs） for plasmonic sensing were manufactured by combining colloidal lithography with metal deposition. In contrast to most previous studies, we shed light on the outstand...Large-area deep-silver-nanowell arrays （d-AgNWAs） for plasmonic sensing were manufactured by combining colloidal lithography with metal deposition. In contrast to most previous studies, we shed light on the outstanding sensitivity afforded by deep metallic nanowells （up to 400 nm in depth）. Using gold nanohole arrays as a mask, a silicon substrate was etched into deep silicon nanowells, which acted as a template for subsequent Ag deposition, resulting in the formation of d-AgNWAs. Various geometric parameters were separately tailored to study the changes in the optical performance and further optimize the sensing ability of the structure. After several rounds of selection, the best sensing d-AgNWA, which had a Ag thickness of 400 nm, template depth of 400 nm, hole diameter of 504 nm, and period of 1 ~m, was selected. It had a sensitivity of 933 nm.RIU-1, which is substantially higher than those of most common thin metallic nanohole arrays. As a proof of concept, the as-prepared structure was employed as a substrate for an antigen-antibody recognition immunoassay, which indicates its great potential for label-free real-time biosensing.展开更多
文摘Refractometric fiber optic sensors have a number of applications in industry due to advantages like remote sensing ability, compact size, easy to fit, etc. A refractometric sensor contains a pair of parallel fibers and a gap between the sensor probe and reflector, wherein the liquid whose refractive index is to be measured is filled. This paper describes the importance of mathematical modeling of this sensor. Ray tracing approach is used to model the sensor mathematically. This mathematical model is generalized for any scenario which is useful to avoid tedious trial and error techniques to design the sensor prototype. Mathematical modelling is a useful tool to optimize the gap distance for a detection of refractive index of liquid. The model is developed and analyzed rigorously considering adulteration of diesel by kerosene where refractive index varies from 1.44 to 1.46. Simulation experiments are carried out to optimize the gap distance which is found to be 6.8 mm using both models. Experiments are carried out where sensor probe is fabricated and results are analyzed. It is observed that for suggested gap distance sensor output varies almost linear over the entire range.
文摘The practical development of compact modern nanophotonic devices relies on the availability of fast and low-cost fabrication techniques applicable to a wide variety of materials and designs.We have engraved a split grating geometry on stainless steel using femtosecond laser processing.This structure serves as a template to fabricate efficient plasmonic sensors,where a thick gold layer is grown conformally on it.The scanning electron microscope(SEM)images confirm the generation of the split laser-induced periodic spatial structures.The optical reflectance of our sensors shows two dips corresponding to the excitation of surface plasmon resonances(SPRs)at two different wavelengths.Furthermore,the asymmetric shape of these spectral responses reveals a strong and narrow Fano resonance.Our computational electromagnetism models accurately reproduce the reflectivity of the fabricated structure.The spectral responses of both the simulated and fabricated structures are fitted to the Fano model that coherently combines the narrow SPRs with the broad continuum background caused by diffraction.The parameters extracted from the fitting,such as the resonance wavelengths and line widths,are used to evaluate the performance of our device as a refractometric sensor for liquids.The maximum sensitivity and figure of merit are 880 nm/RIU and 80 RIU-1,respectively.Besides the compact design of our sensing device,its performance exceeds the theoretical maximum sensitivity of a classical Kretschmann setup.
基金This work was financially supported by the National Basic Research Program of China （973 program, No. 2012CB933800） and the National Natural Science Foundation of China （NSFC, No. 91123031）.
文摘Large-area deep-silver-nanowell arrays （d-AgNWAs） for plasmonic sensing were manufactured by combining colloidal lithography with metal deposition. In contrast to most previous studies, we shed light on the outstanding sensitivity afforded by deep metallic nanowells （up to 400 nm in depth）. Using gold nanohole arrays as a mask, a silicon substrate was etched into deep silicon nanowells, which acted as a template for subsequent Ag deposition, resulting in the formation of d-AgNWAs. Various geometric parameters were separately tailored to study the changes in the optical performance and further optimize the sensing ability of the structure. After several rounds of selection, the best sensing d-AgNWA, which had a Ag thickness of 400 nm, template depth of 400 nm, hole diameter of 504 nm, and period of 1 ~m, was selected. It had a sensitivity of 933 nm.RIU-1, which is substantially higher than those of most common thin metallic nanohole arrays. As a proof of concept, the as-prepared structure was employed as a substrate for an antigen-antibody recognition immunoassay, which indicates its great potential for label-free real-time biosensing.
