Ring Resonator Explorer
Simulate, measure, and fit microring resonators in one place: FSR, FWHM, loaded and intrinsic Q, finesse, extinction, coupling regime, transmission phase, group delay, and the true-scale circulating field, all live from the coupled-mode transfer functions. Then paste a measured wavelength scan and the same model fits your data: Q, extinction, κ², and propagation loss, with both coupling branches reported.
Five two-minute experiments. Each one sets the controls, tells you where to look, and asks you to predict before it shows you.
True-scale steady-state field of the device. The transverse profile is the EIM lateral mode of a 500×220 nm SOI wire (evanescent decay 112 nm), carried along the circuit with the same coupled-mode amplitudes the spectrum is built from, at the real guided wavelength, so the fringes, the tails, and their overlap in the coupling gap are physical. The intensity view is quantitative on a 30 dB log scale; the field view is contrast-compressed for visibility. Drawn approximations: the straight-guide profile is applied unchanged along the bend, the 200 nm gap is illustrative (κ comes from the slider, not the drawn gap), and propagation is slowed by roughly 1013.
Paste a wavelength scan (two columns: λ then transmission, CSV, TSV, or space-separated; nm/µm/m and dB/linear are auto-detected), or load a file. The tool normalizes the baseline, finds the resonances, fits each to the all-pass lineshape, and extracts Q, extinction, and, using the R and ng set in the controls, κ² and propagation loss for both coupling branches. A power spectrum alone cannot say which branch is real: that is the under/overcoupled ambiguity, and resolving it takes a phase measurement or a trend across wavelength (see the phase panel).
Extraction method: fit FWHM and on-resonance transmission, then invert the all-pass model for the (r, a) pair; the two orderings are the two branches, per W. McKinnon et al., “Extracting coupling and loss coefficients from a ring resonator,” Opt. Express 17, 18971 (2009). Files are read locally in your browser and never leave your machine.
On every load this page re-evaluates a fixed reference case (λ₀ = 1550 nm, R = 10 µm, neff = 2.44, ng = 4.2, α = 3 dB/cm, κ² = 1%) with its own code and compares the result to values computed independently in Python from the same equations, plus one internal identity: at critical coupling the loaded Q must equal half the intrinsic Q. The two EIM rows check the embedded slab solver that draws the field view’s transverse mode profile against the same solve run independently in Python.
FSR is the wavelength spacing between resonances, λ²/ngL; higher Q does not change it. Loaded Q is what a transmission scan measures (λ/FWHM); intrinsic Q is what the ring would show with the coupler removed, set by loss alone, and the two are related through the coupling regime. Finesse is FSR/FWHM, the number of resolvable lines per period. Critical coupling is κ² equal to the round-trip loss: the through port nulls and extinction diverges. Photon lifetime τp = Qλ/2πc is the linewidth’s time-domain twin: energy stored in the ring decays with this constant.
Transfer functions are the standard coupled-mode results for a single ring: all-pass T = (a² − 2ra·cosφ + r²) / (1 − 2ra·cosφ + (ra)²) and the corresponding add-drop pair, with r² + κ² = 1 (lossless coupler), a² = e−αL, and round-trip phase φ = 2πneff(λ)L/λ. These are exact for the stated model; the physics approximations live in the inputs.
Assumed: single mode, coupling independent of wavelength across the 10 nm window, first-order dispersion only (constant ng), no thermal or nonlinear effects, and α taken as the total round-trip loss, so bend loss is included in the number you enter rather than modeled from R. Moving λ₀ to another band does not update the material inputs for you: neff, ng, and α are whatever you enter, stated at λ₀, and the field view’s transverse profile stays the 1550 nm solve.
Equations follow W. Bogaerts et al., “Silicon microring resonators,” Laser & Photonics Reviews 6, 47–73 (2012).
Runs entirely in your browser. Nothing you enter is uploaded or stored.