Abstract
We report the fabrication of in-line photonic microcells (PMCs) by encapsulating tapered microfibers (MFs) inside glass tubes. The encapsulation isolates MFs from external environment and makes them more suitable for real-world applications. Based on PMCs with encapsulated highly birefringent (Hi-Bi) MFs, we demonstrated pressure, temperature and refractive index (RI) sensors as well as long period grating devices. A fiber Sagnac loop interferometer incorporating a Hi-Bi microfiber PMC demonstrated RI sensitivity of 2024 nm per RI unit (nm/RIU) in gaseous environment and 21231 nm/RIU in water.
Highlights
Microfiber (MF) photonic devices have attracted considerable attention recently
The optical performance of the MFs degrades quickly due to light scattering from dust particles and cracks induced by water vapor, and an increasing unrecoverable optical loss was observed over time if they are left in open air [7,8]
To illustrate the potential applications of such photonic microcells (PMCs), we demonstrated refractive index (RI) sensors by incorporating an encapsulated highly birefringent (Hi-Bi) microfiber PMC into a fiber-optic Sagnac loop interferometer (SLI) and achieved RI sensitivity of 2024 nm per RI unit (RIU) around RI = 1 and 21231 nm/RIU around RI = 1.33
Summary
Microfiber (MF) photonic devices have attracted considerable attention recently. Various MF-based devices such as microfiber resonators and add/drop filters [1,2,3], supercontinnum sources [4], refractometric sensors, and photoacoustic gas detectors [5,6] have been reported. Side holes are made on the capillary wall, which act as ingress/egress channels for sample liquids or gases Such PMCs are robust and stable, and can be integrated into standard fiber-optic circuits with low loss, making the MF-based devices more practical for real-world applications. It is a home-made tapering-rig based on the well-known flame-brushing technique, and this technique is popularly used to taper-draw MFs from conventional SMFs [9]. The embedment improves robustness, stability of the MFs and protects them from environmental degradation It brought some challenges, including complicated embedding process, additional optical loss [10,11], undesirable changes in light confinement and dispersion [10,12], and incapability of accessing to the evanescent field. It should be pointed out that the PMCs are suitable for straight MFs and MF-based devices and they cannot be used to house MF knots and loops [1, 3]
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