Abstract
A laser-assisted tuning method of whispering gallery modes (WGMs) in a cylindrical microresonator based on magnetic-fluids-infiltrated microstructured optical fibres (MFIMOFs, where MF and MOF respectively refer to magnetic fluid and microstructured optical fibre) is proposed, experimentally demonstrated and theoretically analysed in detail. The MFIMOF is prepared by infiltrating the air-hole array of the MOF using capillary action effect. A fibre-coupling system is set up for the proposed MFIMOF-based microresonator to acquire an extinction ratio up to 25 dB and a Q-factor as large as 4.0 × 104. For the MF-infiltrated MOF, the light propagating in the fibre core region would rapidly spread out and would be absorbed by the MF-rod array cladding to induce significant thermal effect. This has been exploited to achieve a WGM resonance wavelength sensitivity of 0.034 nm/mW, which is ~20 times higher than it counterpart without MF infiltration. The wavelength response of the resonance dips exhibit linear power dependence, and owing to such desirable merits as ease of fabrication, high sensitivity and laser-assisted tunability, the proposed optical tuning approach of WGMs in the MFIMOF would find promising applications in the areas of optical filtering, sensing, and signal processing, as well as future all-optical networking systems.
Highlights
In this paper, we have presented a whispering gallery mode (WGM) microresonator based on a magnetic fluid (MF) infiltrated MOF (MFIMOF)
We have presented a WGM microresonator based on a magnetic fluid (MF) infiltrated MOF (MFIMOF)
Owing to the mode overlapping between the taper evanescent field and the WGMs in the MFIMOF, part of the evanescent field would be coupled into the WGMs propagating inside the microresonator around the contact region
Summary
We have presented a WGM microresonator based on a magnetic fluid (MF) infiltrated MOF (MFIMOF). Since the refractive index of the deep coloured MFs is close to the silica background, the MOF-based microresonator could be regarded as a cylindrical cavity resonator comprising strongly thermal absorption medium. Based on this simplification, we calculate the orders of the WGM eigenmodes supported by the proposed MOF-based microresonator, which is in good agreement with our experimental observation. Our proposed MOF-based microresonator possesses several desirable features such as highly sensitive laser-assisted tunability, high linear power dependence and ease of fabrication, which make it a good candidate for potential applications in the areas of optical filtering, sensing, and signal processing as well as future all-optical networking systems
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