Figure 1

(Color online) (a) shows a SEM picture of an investigated sample of two coupled disks. (b) shows the sketch of the 2D representation of the structure with notations of radii and the calculated expansion coefficients (the thick arrow marks the excited mode). The lower two pictures show the calculated spectra of the $b_{\pm 103}^{\left(1,2\right)}$ expansion coefficients for the scattered field of first (c) and second (d) disks for varying radius of second disk (single disk resonance at $1.5533\mu \text{m}$ with $m=103$) exhibiting splitting of the resonances. The white solid lines show the real part of the coefficients along the dashed white lines for equal radii of $20\mu \text{m}$. In this case, light intensity is equal in both disks for both resonances.Reuse & Permissions

Figure 2

(Color online) Solution of dispersion relation (13) for the case of six coupled disks, showing two branches of normal quasimodes, characterized by complex-valued frequencies [left (right) graph shows real (imaginary) part]. The dashed arrows mark the normal frequencies and the two corresponding modes from the two branches.Reuse & Permissions

Figure 3

(Color online) Measured spectral response of a single disk resonator for both polarization states (TE: blue solid line, TM: red dashed line). The blue dots (TE) and red crosses (TM) are the calculated resonance wavelengths [above (below) the gray line from the 2D-effective index (FEM) model] with the corresponding azimuthal mode numbers $m$. The stronger resonances are fundamental (high $Q$) modes with large $m$. The weaker excited resonances are second-order radial modes (two intensity maxima in radial direction) with lower values of $m$. Due to the good agreement for the relative distances of differently polarized modes, the measured resonances can be identified.Reuse & Permissions

Figure 4

(Color online) Comparison of measured resonances with theoretical calculations for two coupled disk resonators with different gap sizes (1000 nm [(a) and (b)], 500 nm [(c) and (d)], and 300 nm [(e) and (f)]). In each graph, the blue line represents the measured transmission signal through the taper. The black lines represent the calculated $1-\left|b_m^{\left(1,2\right)}\right|$, where $\left|b_m^{\left(1,2\right)}\right|$ are the normalized expansion coefficients of the scattered field of the first (solid line) and second (dashed-dotted line) disks. The insets show the images created by the infrared scattered light from both disks (the left inset in each graph corresponds to the left resonance, the right inset to the right resonance). The locations of the disks are marked by the green circles and the corresponding numbers. The tapered fiber is highlighted by a straight green line (in the upper graphs [(a), (c), and (e)] the first disk is excited; in the lower graphs [(b), (d), and (f)] the second disk is excited).Reuse & Permissions

Figure 5

(Color online) Calculated resonance splitting in the expansion coefficient for the scattered field of first (a), second (b), and third (c) disks of a linear chain of three coupled disks for varying radius of the second disk (single disk resonance at $1.553\mu \text{m}$ with $m=103$). The white solid line in each figure shows the real part of the coefficient along the dashed white line for equal radii.Reuse & Permissions

Figure 6

(Color online) Measured spectral response of a linear chain of three coupled disks (blue line) shows splitting in three resonance dips. Good agreement can be observed for the calculated resonances (black solid line: first disk; black dashed-dotted line: middle disk; and black dotted line: third disk). For the corresponding resonances (A,B,C), the measured light distribution along the chain is plotted in the lower three figures. The relative strength of the calculated expansion coefficients $\left|b_m^{\left(1,2,3\right)}\right|$ of each disk agrees well with the measurement [especially for the middle (b) and long-wavelength (c) resonance].Reuse & Permissions