Three-ring photonic molecule, schematically
Three-ring photonic molecule,
2D simulations of configurations with the following specification: background refractive index 1.0, refractive index of the guiding regions 1.5, waveguide core widths 0.6 µm (bus), 0.75 µm (cavities), cavity radius 7.5 µm (outer rim), gaps 0.3 µm. All calculations are meant for TE polarization, i.e. for a single nonvanishing electrical field component, perpendicular to the plane of the computational window.  

The approximate (!) HCMT model relies on a field template that includes the radially fundamental whispering gallery modes of angular order +/-39 (two WGMs per cavity, resonance wavelength 1.5637 µm), together with directional variants of the bus waveguides slab modes (amplitudes discretized by 1-D finite elements).

Transmission spectrum:
T and R are the guided wave transmittance and reflectance, respectively, for excitation at vacuum wavelength λ in the lower port. The links at the positions indicated by the gray tick marks lead to illustrations of the time harmonic electric field.

1.55969 µm 1.56174 µm 1.56661 µm 1.56914 µm 1.56055 µm 1.56420 µm 1.56812 µm 1.56946 µm 1.56715 µm 1.56235 µm 1.55988 µm 1.56920 µm 1.56715 µm 1.56660 µm 1.56235 µm 1.56176 µm 1.55959 µm

The upper markers indicate supermode eigenfrequencies, determined with an HCMT ansatz for the molecule only (WGMs, black), and for the full composite configuration (WGMs & bus, blue; here also the associated linewidth is shown). The links lead to animations of the corresponding fields. Note that these are modes with complex eigenfrequencies; the animations merely rerun one oscillation at the resonance wavelength, i.e. neglect the (slow) field decay.