Bidirectional tuning of whispering gallery modes in a silica microbubble infiltrated with magnetic fluids

Abstract

A bidirectional tuning mechanism of whispering gallery modes (WGMs) in a capillary-based microbubble microresonator infiltrated with magnetic fluids (MFs) is investigated. Owing to distinct RI responses of MFs dependent on the applied magnetic field direction with respect to the capillary axis, the RI of MFs shows different variation trends when an external magnetic field is parallel or perpendicular to the capillary axis. Experimental results indicate that WGM resonance dips exhibit wavelength shift in inverse directions for the above two cases, which is in accordance with our theoretical analysis on different refractive variation behaviors of MFs. As the applied magnetic field is perpendicular or parallel to the capillary axis, the WGM resonance wavelength tuning sensitivities tend to be − 15.01 p m / m T and 6.3 pm/mT, respectively. Our proposed WGM tuning scheme has several desirable advantages, including bidirectional tunability, high Q-factor, ease of fabrication, and good compatibility with functional materials, making it a promising candidate in the field of magnetic field vector sensing and magnetically manipulated micro-optic devices.

High sensitivity magnetic field sensing via a sandwich-type polydimethylsiloxane resonator

“…The blue-shift sensitivities are 0.322, 1.12, and 0.564 nm∕mT. Other reported resonator sensors, including photonic crystal fibers (53 pm∕mT), 14 microring resonators (−16.80 pm∕mT), 31 microbubble resonators (−15.01 pm∕mT), 13 cylindrical resonators (−61.86 pm∕mT), 12 and microbottle resonators (304.80 pm∕mT). 15 It can be seen that most of the magnetic sensitivities are <1 nm∕mT.…”

“…Recently, magnetic fluids have been combined with photonic crystal fibers or capillary microbubbles with an applied magnetic field perpendicular or parallel to the capillary axis to achieve bidirectional magnetic field detection. [12][13][14][15][16] The method of transmission spectrum shift affects the detection limit. 10 Optical cavity coupled with magnetic material is other type.…”

Magnetic Field Sensing Based on Whispering Gallery Mode with Nanostructured Magnetic Fluid-Infiltrated Photonic Crystal Fiber

“…In recent years, the optical whispering gallery mode (WGM) resonator has shown enormous potential in sensing applications, such as biology [ 15 , 16 , 17 ], temperature [ 18 , 19 , 20 ], gas [ 21 ], humidity [ 22 ], laser [ 23 ], and magnetic field sensing [ 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 ]. Compared with the traditional optical resonators, the WGM resonator possesses high quality factor (Q), small mode volume and long lifetime of quantum photons.…”