Photonic Crystal Fiber With Two Infiltrated Air Holes for Temperature Sensing With Excellent Temporal Stability

Abstract

A photonic crystal fiber sensor is created by infiltrating liquid with higher refractive index than background silica into two adjacent air holes situated in different layers. When the refractive index of the liquid is decreased to that of silica by heating, the two liquid rods and the solid core form a three-parallel-waveguide structure, which enables efficient mode energy coupling between the two eigenmodes and results in an interference fringe pattern. Theoretical analysis has been carried out to reveal the modes involved in the interference. Moreover, the temporal stability of the device is enhanced by inserting short sections of ultraviolet curable glue at both ends of the liquid, followed by solidification, to prevent the liquid-air interface fluctuation. The temperature sensitivity achieved is nm/ C, in the range between 45 and 50 C.Index Terms-Femtosecond (fs) laser ablation, optical fiber interferometer, optical fiber sensors, photonic crystal fiber (PCF).

Unique Temperature Dependence of Selectively Liquid-Crystal-Filled Photonic Crystal Fibers

“…Therefore, experimental sensitivity exceeding 40.2 nm/˚C is achieved. The highest sensitivity for temperature is up to 40.2 nm/˚C at 57.3 ˚C, which is at least 10 times larger than the literature reported in [15][16], 3 times larger than that reported in [20][21] as well. More interesting, the observed trend of λres1 is different with that was previously reported [22][23].…”

“…In special, we experimentally observed that the SLCPCF transmissions follows different trends within the LC phase, where the shift of the resonant wavelengths can be described with a quadratic function, and the isotropic phase, where the shift of the resonant wavelengths can be described with a linear function. The temperature sensitivity of the reported fiber (with a selectively filled channel) was 3-10 times higher than in fibers previously studied [15][16][20][21].…”

Infiltrated Photonic Crystal Fibers for Sensing Applications

“…Better performance was achieved by employing a dual-core PCF scheme, as discussed in the context of refractometric sensors. A fully infiltrated dual-solid core demonstrated a sensitivity of 1.9 nm/°C for a 2-cm-long fiber [154], whereas a directional coupler formed among a solid PCF core and two infiltrated capillaries allowed for a sensitivity of 8.8 nm/°C with very good temporal stability [134]. An enhanced sensitivity of 54.3 nm/°C was demonstrated in Ref.…”

Optofluidic devices with programmable and responsive functions

“…2,4,13,103 The ease of infiltrating liquid with a high thermo-optic coefficient into air holes enables optofluidic PCF a natural candidate for temperature measurement with better sensitivities. [104][105][106][107][108][109][110] Moreover, most evanescent-wave-based optofluidic PCF sensors for temperature measurement at present, are based on configurations to infiltrate airholes at the innermost cladding layer selectively. [105][106][107] By this means, high-temperature sensitivity can be achieved with an enlarged overlap of the optic field with the liquid rod.…”

“…In the modified DCPCF, the RI of the central liquid rod was slightly higher than the value of silica, resulting in a three-parallel-waveguide structure formed by central liquid rod and two solid cores with narrow waveguide separation, leading to strong coupling between the silica core modes and the liquid core modes. 103,109,110 Besides, the central liquid core in the three-parallel-waveguide structure ensures significant lightmatter interaction, which is beneficial in leveraging the high thermo-optic coefficient of the liquid to achieve high-temperature sensitivity. The proposed waveguide structure with a central core filled with RIL enables mode energy beating and resulted in a dualcomponent interference pattern over a wide wavelength range.…”