Experimental analysis of the whispering-gallery modes in a cylindrical optical microcavity

Abstract

A real-space study of a cylindrical integrated optical microcavity by means of a photon scanning-tunneling microscope with a resolution of 50 nm reveals optical intensity distributions in great detail. Moreover, novel phenomena such as polarization conversion and conversion from copropagation to counterpropagation are observed. We present detailed maps of the optical field distribution of the whispering-gallery modes inside the microcavity as a function of both wavelength and position. We have made a quantitative comparison between measured and calculated field distributions. As a result, the buildup of the various whispering-gallery modes is better understood.

Analytic approach to dielectric optical bent slab waveguides

“…For cylindrical cavities with relatively high radial refractive index contrast, also higher order bend modes can be relevant for an adequate representation of resonant field patterns (Klunder et al 2000(Klunder et al , 2002Balistreri et al 2001). Table 3 summarizes results for propagation constants of fundamental and first-order modes of both polarizations for a nonsymmetric slab with Table 3, absolute values of the basic profile componentẼ y of structures with radii R ¼ 100; 50, and 20 lm.…”

Detailed analysis of the intracavity phenomena inside a cylindrical microresonator

“…The observed subwavelength spatial mode-beat periods give unambiguous evidence of the presence of contradirectionally propagating WGMs and also illustrate the optical resolution of the PSTM nm . We observed relatively deep modulations [11] in the intensity due to the co-and contradirectional mode beat involving the TE1,0 WGM, which indicates a strong excitation of the TE1,0 WGM despite of the high-propagation losses of this WGM.…”

“…In the case where the waveguide and materials dispersion can be ignored, the FSR is analogous to the well-known expression for the FSR of a Fabry-Perot interferometer FSR (11) However, the waveguide dispersion in cylindrical MRs can be quite strong [18]; therefore, we use (10) instead of (11) throughout this paper.…”

“…In all experiments, we checked the consistency between the measured spatial and spectral intensity distributions inside the MR and the measured power at the input and output ports of the MR. For more details on the experiments, the reader is referred to [8], [10], [11].…”

“…From measuring this intensity distribution, as a function of the position in the MR and the wavelength , not only the WGMs themselves can be observed directly [8], [9], but also the interference (i.e., spatial and spectral mode-beat phenomena) between them [8], [10], [11]. Conventional (diffraction limited, ) microscopes, which rely on collecting the power scattered from the MR, cannot provide detailed information about the transversal modal profiles of the WGMs because the lateral dimensions of the WGMs are in the subwavelength regime.…”