PROCEEDINGS ARTICLE | August 21, 2014
Proc. SPIE. 9283, 7th International Symposium on Advanced Optical Manufacturing and Testing Technologies: Design, Manufacturing, and Testing of Micro- and Nano-Optical Devices and Systems
KEYWORDS: Refractive index, Microresonators, Finite-difference time-domain method, Resonators, Waveguides, Coating, Magnetism, Wave propagation, Geometrical optics, Waveguide modes
With the finite difference time domain (FDTD) method, whispering gallery modes (WGM) in a microsphere coated with
three layers of high, low, and high refractive index (RI) are simulated. In the simulation, the coupling system includes a
coating microsphere, a waveguide and a nanoscale gap separating the waveguide and the microsphere. A pulse with
ultra-wide bandwidth that spans over several resonant modes of the resonator is used for simulation. Via waveguide
coupling, the relative intensity spectra of the three layers and the transmission spectrum of the coupling system are
obtained. We investigate the effects of the waveguide RI and the thickness of the low-RI layer on resonance
characteristics. It is found that each of the two high-RI layers can sustain its own WGM if the values of RI and thickness
of the three layers are appropriate. Furthermore, the effect of the RI of the surrounding medium on resonance
characteristics is also studied. The simulation results show that a RI change of the surroundings will only change the
resonance wavelength of the outer layer, and will not affect the WGM of the inner layer. Such property makes it feasible
for a potential application in high-precision RI and temperature sensing.
