Abstract
In this work, we present a gold-coated shallow-tapered chirped fiber Bragg grating (stCFBG) for dual refractive index (RI) and temperature sensing. The stCFBG has been fabricated on a 15-mm long chirped FBG, by tapering a 7.29-mm region with a waist of 39 μm. The spectral analysis shows two distinct regions: a pre-taper region, in which the stCFBG is RI-independent and can be used to detect thermal changes, and a post-taper region, in which the reflectivity increases significantly when the RI increments. We estimate the RI and thermal sensitivities as 382.83 dB/RIU and 9.893 pm/°C, respectively. The cross-talk values are low (−1.54 × 10−3 dB/°C and 568.1 pm/RIU), which allows an almost ideal separation between RI and thermal characteristics. The stCFBG is a compact probe, suitable for long-term and temperature-compensated biosensing and detection of chemical analytes.
Highlights
IntroductionIndex and Temperature Sensing.Optical fiber sensors allow the measurement of physical and biological parameters with high precision and operate in a broad range of environments [1] thanks to their advantageous properties, such as compactness and lightweight form factors, possibility to measure in situ (for example, through packaging in medical devices [2]), immunity to electromagnetic interference which allows the operation during magnetic resonance procedures [3], and excellent safety.Refractive index (RI) sensors find increasing applications in biosensors [4]
Index and Temperature Sensing.Optical fiber sensors allow the measurement of physical and biological parameters with high precision and operate in a broad range of environments [1] thanks to their advantageous properties, such as compactness and lightweight form factors, possibility to measure in situ, immunity to electromagnetic interference which allows the operation during magnetic resonance procedures [3], and excellent safety.Refractive index (RI) sensors find increasing applications in biosensors [4]
We report the design of a shallow-tapered sensor fabricated on a pre-existent chirped FBG (CFBG) [25]
Summary
Index and Temperature Sensing.Optical fiber sensors allow the measurement of physical and biological parameters with high precision and operate in a broad range of environments [1] thanks to their advantageous properties, such as compactness and lightweight form factors, possibility to measure in situ (for example, through packaging in medical devices [2]), immunity to electromagnetic interference which allows the operation during magnetic resonance procedures [3], and excellent safety.Refractive index (RI) sensors find increasing applications in biosensors [4]. RI sensors usually operate in two typologies of environments. A bare RI sensor, or refractometer, is capable of detecting small changes of the analyte surrounding the fiber, by measuring a wavelength shift or intensity change of the reflection or transmission spectrum of the device [5]. RI sensors can be functionalized to the selective detection of a biological analyte, targeting specific biomolecules or cells, such as in the case of immunosensors [6]. The biofunctionalization step, usually performed by a thin-film metallic layer or through silanization [7], enables a selective detection, rather than a simple inspection of the surrounding analyte
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