Abstract
In this paper, a microfiber knot resonator (MKR) was encapsulated in polydimethylsiloxane (PDMS), and its capability to sense temperature was experimentally evaluated. A very high sensitivity of -12 nm/°C was recorded for the MKR device, with a microfiber diameter of 2μm and a ring diameter of 95 μm. However, light-loss was significant in the small MKR. We attribute this to the low ratio of ring-length to microfiber-diameter. A stable temperature-sensing performance and sensitivity of negative 8.48 nm/°C were obtained for the MKRs with a microfiber diameter of 3 μm and a ring diameter of 3 mm. A MKR device with a non-uniform microfiber (in diameter) was also fabricated and studied. This compact and miniature temperature-probe will be a promising candidate for wearable devices.
Highlights
Optical fiber sensors attract the interest of researchers worldwide because of their electromagnetic resilience, chemical-corrosion resistance, high integration-ability, high sensitivity, remote-sensing ability, low price, and their suitability for mass production [1]–[3]
The microfiber knot resonator (MKR) temperature sensors based on silica or polymer materials perform a fast response
By reducing the ring length of the microfiber and ensuring the uniformity of the microfiber diameter, a temperature sensitivity of 8.48 nm/°C is experimentally confirmed for a PDMS encapsulated MKR with a ring diameter of 3 mm
Summary
Optical fiber sensors attract the interest of researchers worldwide because of their electromagnetic resilience, chemical-corrosion resistance, high integration-ability, high sensitivity, remote-sensing ability, low price, and their suitability for mass production [1]–[3]. Made of micro/nanofiber, miniature fiber-sensors, with their fast response, low transmission-loss, and compact dimensions, currently dominate the sensing field [4], [5] They are widely used to measure gas, humidity, temperature, stress, magnetic fields, refractive indexes, and other parameters [6]–[8]. Compared with the tapered microfiber, whose sensing performance only depends on the change of the external refractive index, in addition MKR structure introduces another parameter, named ing length, to further improve the sensitivity. Sheets to improve their structural stability [12] Based on their theoretical and experimental results, the temperature response of the MKR depended strongly on the diameter of the microfiber as well as the refractive index and thermal optical-coefficient of the external medium. The MKR temperature sensors based on silica or polymer materials perform a fast response. By reducing the ring length of the microfiber and ensuring the uniformity of the microfiber diameter, a temperature sensitivity of 8.48 nm/°C is experimentally confirmed for a PDMS encapsulated MKR with a ring diameter of 3 mm
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