Hollow-bottle optical microresonators

Abstract

Selective excitation of whispering-gallery and bottle modes in a robust hollow-bottle optical microresonator, fabricated from a silica microcapillary by a pressure-compensated, "soften-and-compress" method, is demonstrated. Characteristic resonance spectra of bottle modes were obtained by using a tapered fiber coupled at different locations along the hollow bottle. The spectral characteristics (Q-factor, excitation efficiency) are shown to have high tolerance to angular misalignment of the tapered fiber. In addition, introduction of localized losses on the outer surface of the resonator results in selective clean-up of the transmission spectrum and superior performance. A theoretical analysis of modal turning points and associated resonant wavelengths is used to explain the mechanism of mode-suppression and the resultant spectral cleaning.

Microcavity morphology optimization

“…1(a). Equation (3) shows that geometrical change of the resonator radius is equivalent to the spatially dependent increase of the refractive index of the resonator host material. Introducing = r z , we separate variables where k 2 z is the separation parameter.…”

“…This is an undesirable feature for various applications. For instance, when a cavity is used as a linear optical filter, high-order modes result in additional undesirable frequency-dependent rejection or transmission of a signal of interest, reducing the efficacy of the filter [2][3][4]. High-order modes also lead to mode competition in lasers [5] and tend to cause unwanted nonlinear instabilities in optical sensors and oscillators.…”

Detection and Digital Resolution Counting of Nanoparticles with Optical Resonators and Applications in Biosensing

“…The presence of a nanoparticle on the perimeter of the WSG sensor is also capable of scattering light which can propagate in the reverse direction, causing a single initial WSG mode to split into multiple counterpropagating modes. The ability to resolve modal wavelength shifts ranging from 0.1 pm to several nanometers, in combination with extremely small modal volumes, has generated broad interest in WSG-based sensing, with a variety of geometries such as spheres [97][98][99], droplets [100], disks [101][102][103][104][105][106], rings [107,108], bottles [109], bubbles [110][111][112], and capillaries [113,114].…”

Optical Microbottle Resonators for Sensing

“…The uniformity of the resulting microbottles is improved when using two CO${}_2$ lasers [28]. The “soften-and-compress” [21] method has also been applied to the fabrication of hollow microbottles, adding a moderate pressurization of the capillary to the splicer-based method [29]. For sensing purposes, it might be desirable to make microbottles with very thin walls.…”

“…All rights reserved); ( b ) “soften-and-compress” method used with a capillary. Image reprinted with permission from [29] (©The Optical Society of America); ( c ) reduction of a capillary’s diameter on the sides using a CO${}_2$ laser. Image reprinted with permission from [14] (©The Optical Society of America).…”