Abstract:Selective excitation of spheroidal whispering gallery modes and bottle modes in a robust bottle microresonator fabricated straightforwardly from a short section of optical fiber is demonstrated. Characteristic resonance spectra of long-cavity bottle modes were obtained by using a tapered fiber to excite evanescently bottle microresonator at different points along its axis. Compared to bare-fiber cylindrical resonators, the bottle microresonator results in a 35x increase of the observed Q factor.
“…From the relation between PNJ attributive characteristics and microparticle boundary curvatures, PNJ can be further modulated by changing the microparticle boundary profiles, as show in Fig. 4a for four shape profiles: C-type (circular), P-type (parabolic), H-type (Harmonic-oscillating 25 ) and L-type (linear). The inset at the top of Fig.…”
Section: Resultsmentioning
confidence: 99%
“…f
C , f
P and f
H ; ω
C , ω
P , ω
H are respectively the focal points and beam widths of the generated PNJs from these three profiled R-MPCMs. Choice of P-type and H-type profiles, as optimization options, is mainly due to the consideration of developing three-dimensional (3D) high- Ri superlens with controllable heating-and-deforming or self-assembling methods in the future 25–27 .Figure 4( a ) Four boundary profiles for narrowing the transverse beam widths of the PNJs. C-type: circular type, P-type: parabolic type, H-type: harmonic-oscillating type, L-type: linear type.…”
In general, photonic nanojets (PNJs) occur only when the refractive index (Ri) difference between the microparticle and background media is less than 2. The minimum full width at half-maximum (FWHM) of the PNJ is ~130 nm (approximately one-third of the illumination wavelength λ = 400 nm) formed within the evanescent field region. This paper proposes and studies a method to overstep the Ri upper bound and generate ultra-narrow PNJs. Finite element method based numerical investigations and ray-optics theoretical analyses have realized ultra-narrow PNJs with FWHM as small as 114.7 nm (0.287 λ) obtained from an edge-cut, length-reduced and parabolic-profiled microparticle with Ri = 2.5 beyond evanescent decay length. Using simple strain or compression operations, sub-diffraction-limited PNJs can be flexibly tuned on the order of several wavelengths. Such ultra-narrow PNJs offer great prospects for optical nonlinearity enhancements of greater enhancing effect, optical nanoscopy of higher spatial resolution, optical microprobes of smaller measurement accuracy, nano/micro-sized sample detections of higher sensing sensitivity, nanoscale objects of more accurate control, advanced manufactures of smaller processing size, optical-disk storage of larger data capacity and all-optical switching of lower energy consumption.
“…From the relation between PNJ attributive characteristics and microparticle boundary curvatures, PNJ can be further modulated by changing the microparticle boundary profiles, as show in Fig. 4a for four shape profiles: C-type (circular), P-type (parabolic), H-type (Harmonic-oscillating 25 ) and L-type (linear). The inset at the top of Fig.…”
Section: Resultsmentioning
confidence: 99%
“…f
C , f
P and f
H ; ω
C , ω
P , ω
H are respectively the focal points and beam widths of the generated PNJs from these three profiled R-MPCMs. Choice of P-type and H-type profiles, as optimization options, is mainly due to the consideration of developing three-dimensional (3D) high- Ri superlens with controllable heating-and-deforming or self-assembling methods in the future 25–27 .Figure 4( a ) Four boundary profiles for narrowing the transverse beam widths of the PNJs. C-type: circular type, P-type: parabolic type, H-type: harmonic-oscillating type, L-type: linear type.…”
In general, photonic nanojets (PNJs) occur only when the refractive index (Ri) difference between the microparticle and background media is less than 2. The minimum full width at half-maximum (FWHM) of the PNJ is ~130 nm (approximately one-third of the illumination wavelength λ = 400 nm) formed within the evanescent field region. This paper proposes and studies a method to overstep the Ri upper bound and generate ultra-narrow PNJs. Finite element method based numerical investigations and ray-optics theoretical analyses have realized ultra-narrow PNJs with FWHM as small as 114.7 nm (0.287 λ) obtained from an edge-cut, length-reduced and parabolic-profiled microparticle with Ri = 2.5 beyond evanescent decay length. Using simple strain or compression operations, sub-diffraction-limited PNJs can be flexibly tuned on the order of several wavelengths. Such ultra-narrow PNJs offer great prospects for optical nonlinearity enhancements of greater enhancing effect, optical nanoscopy of higher spatial resolution, optical microprobes of smaller measurement accuracy, nano/micro-sized sample detections of higher sensing sensitivity, nanoscale objects of more accurate control, advanced manufactures of smaller processing size, optical-disk storage of larger data capacity and all-optical switching of lower energy consumption.
“…Instead of heating and pulling, it has been shown that it is possible to obtain microbottles reversing the mechanical motion; that is, with a “soften and compress” method [21]. …”
Section: Fabrication and Characterizationmentioning
confidence: 99%
“…The uniformity of the resulting microbottles is improved when using two CO 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.…”
Section: Fabrication and Characterizationmentioning
Whispering gallery mode (WGM) optical microresonators have been shown to be the basis for sensors able to detect minute changes in their environment. This has made them a well-established platform for highly sensitive physical, chemical, and biological sensors. Microbottle resonators (MBR) are a type of WGM optical microresonator. They share characteristics with other, more established, resonator geometries such as cylinders and spheres, while presenting their unique spectral signature and other distinguishing features. In this review, we discuss recent advances in the theory and fabrication of different kinds of MBRs, including hollow ones, and their application to optofluidic sensing.
Microlasers have experienced tremendous development in the past decade and become an essential part in laser evolution, as miniature lasers provide strong optical confinement and feature greatly enhanced light–matter interactions. Among all the configurations, whispering gallery mode (WGM) microcavities and microlasers exhibit outstanding optical performances with high quality factors and small mode volumes, thus ensuring low lasing thresholds. In addition, some unique properties inherent to WGM cavities, like bi‐directional propagation and an evanescent field that spans several hundred nanometers across the boundary, can be exploited for novel applications. Therefore, designing and engineering innovative WGM microcavities and microlasers has attracted increasing research interest. The fundamentals and characteristics of WGM are introduced here, and then the developments and current status of WGM microcavities and microlasers are reviewed in terms of the evolution of fabrication techniques and built‐up materials. In particular, the melting of glassy materials in early studies, top‐down and bottom‐up approaches with semiconductors, coating structures, as well as flexible, soft microresonators in recent years are presented. Finally, the application prospects of microlasers including the wavelength manipulation, sensing and microresonator coupling, are discussed.
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