title: Compact and cost-effective temperature-insensitive bio-sensor based on long-period fiber gratings for accurate detection of E. coli bacteria in water.
abstract: We propose and demonstrate a novel temperature-insensitive bio-sensor for accurate and quantitative detection of Escherichia coli (E. coli) bacteria in water. Surface sensitivity is maximized by operating the long-period fiber grating (LPFG) closest to its turnaround wavelength, and the temperature insensitivity is achieved by selectively exciting a pair of cladding modes with opposite dispersion characteristics. Our sensor shows a nominal temperature sensitivity of ∼1.25  pm/°C, which can be further reduced by properly adjusting the LPFG lengths, while maintaining a high refractive index sensitivity of 1929 nm/RIU. The overall length of the sensor is ∼3.6  cm, making it ideally suitable for bio-sensing applications. As an example, we also show the sensor's capability for reliable, quantitative detection of E. coli bacteria in water over a temperature fluctuation of room temperature to 40°C.
authors.forename: Krishnendu
authors.initials: K
authors.lastname: Dandapat
authors.forename: Saurabh Mani
authors.initials: SM
authors.lastname: Tripathi
authors.forename: Yasser
authors.initials: Y
authors.lastname: Chinifooroshan
authors.forename: Wojtek J
authors.initials: WJ
authors.lastname: Bock
authors.forename: Predrag
authors.initials: P
authors.lastname: Mikulic
mesh_terms: D015374:Biosensing Techniques; D004926:Escherichia coli; D005336:Fiber Optic Technology; D055100:Optical Fibers; D012031:Refractometry; D013696:Temperature; D014867:Water
chemical_list: D014867:Water