Microbottle Resonator Research Articles

Nanoparticle detection by mode splitting in hollow bottle microresonators

Mode splitting (MS) in whispering gallery microresonators provides excellent noise suppression in sensing signal compared to mode shifting. Here, we theoretically studied the ability of hollow bottle microresonators for detection of a single nanoparticle in air and water medium by MS phenomenon. To find out the optimum condition of sensor for nanoparticle (NP) detection, the effects of bottle geometry parameters, mode orders, and mode polarization state was investigated. The first radial transverse electric mode demonstrated the best sensitivity when the resonator radius and wall thickness were 10 and 0.3 μm, respectively. However, transverse magnetic modes manifested slightly better detection limit. In the air core hollow microbottle resonator (HMBR), the best detection limit of 3.1 nm radius for polystyrene NPs was achieved at an optimum condition of 30-μm resonator radius and 0.8-μm wall thickness. While MS could not be resolved in deionized water filled HMBRs for all of the investigated conditions at 1550 nm, changing the wavelength to 780 nm provided a detection limit of 15.1 nm in water. Furthermore, it is found that the sensitivity of HMBR is increased by at least two times in comparison with a microtoroid sensor. HMBRs are optofluidic platforms, so employing them could drastically enhance the applicability of microresonator-based systems for label-free NP detection.

Mode-selective lasing in high-Q polymer micro bottle resonators.

Passive and active polymer micro bottle resonators (MBRs) are fabricated. Equatorial whispering gallery modes and bottle modes are clearly identified, with highest loaded quality (Q) factor above 10(5). Lasing with threshold as low as 1 nJ/pulse is realized in active MBRs. Mode selective lasing is achieved by coupling a tapered fiber to equatorial whispering gallery modes or a group of bottle modes. The bottle mode free spectral range (FSR) is found to be about one fifth of the equatorial modes.

Polymer based planar coupling of self-assembled bottle microresonators

The investigation of a simple and self-assembling method for realizing polymeric micro-bottle resonators is reported. By dispensing precise amounts of SU-8 onto a cleaved optical fiber, employed as mechanical support, bottle microcavities with different shapes and diameters are fabricated. The balancing of surface energy between glass fiber and polymeric microresonator with surface tension of SU-8 confers different shape to these microstructures. Planar single-mode SU-8 based waveguide, realized on polymethylmethacrylate, is chosen for exciting the micro-bottle resonators by evanescent wave. The reliability of the fabrication process and the shape of the bottle microcavities are investigated through optical analysis. We observe whispering gallery modes in these resonant microstructures by a robust coupling with single mode planar waveguides around 1.5 μm wavelength. The resonance spectra of micro-bottle resonators and the spectral characteristics, such as Quality-factor (Q factor) and free spectral range, are evaluated for all the realized microstructures. SU-8 micro-bottle resonators show high Q-factors up to 3.8 × 104 and present a good mechanical stability. These features make these microcavities attractive for sensing and/or lasing applications in a planar platform.

Reversible nonmagnetic single-photon isolation using unbalanced quantum coupling

The nonreciprocal propagation of light at the single-photon level is essential for building a quantum network. Bulk optical schemes are lossy and difficulty to integrate onto a chip. We propose a single-photon optical diode and a three-port circulator without a magnetic field by coupling an unbalanced quantum impurity to a passive, linear optical waveguide or a whispering-gallery-mode microresonator which supports a locally or globally circularly polarized photon. Thanks to the unbalanced quantum Jaynes-Cummings coupling, the optical nonreciprocal propagation of single photons can be achieved without an external magnetic field. In particular, the three-port single-photon circulator can be accomplished using the existing experimental technology. The optical isolation can be reversed by selectively populating the initial state of the quantum impurity. Moreover, by using an ensemble of identical atoms filled in a hollow-core microbottle resonator, nonreciprocal propagation of weak light pulses can be achieved.

Ultralow sensing limit in optofluidic micro-bottle resonator biosensor by self-referenced differential-mode detection scheme

Biosensors based on optofluidic micro-bottle resonators are demonstrated. A self-referenced sensing scheme, differential mode sensing, is proposed and used to substantially suppress environmental noises and reach an ultralow noise equal detection limit of 10 fg/ml (∼0.15 fM) for bovine serum albumin molecules. This sensing scheme has high compatibility with any other microcavity sensors to get lower biosensing limit.