Photonic Integrated Circuit Simulator

Photonic Chip

Ring coupling κ 0.30

Wavelength λ 1547.00 nm

Phase shift Δφ 0.00π (0.0 V)

Ring transmission spectrumdip −0 dB

Through bus (post-ring)

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Ring buildup

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Output — Bar

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Output — Cross

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How it works

Light enters a bus waveguide and passes a ring resonator side-coupled through a directional coupler. Only wavelengths that complete a whole number of round trips in phase build up inside the ring and get pulled out of the bus, so the through-power dips sharply at each resonance — the notch you see sweeping in the spectrum plot as λ changes. The coupling slider sets how strongly the bus and ring exchange power: too weak (under-coupled) or too strong (over-coupled) both leave a shallow dip; there is a sweet spot — critical coupling — where the dip goes almost to zero.

φ_ring = 2π(λ−λ0)/FSR
T = (a² − 2at·cosφ + t²) / (1 − 2at·cosφ + (at)²)
bar   ∝ T·cos²(Δφ/2)
cross ∝ T·sin²(Δφ/2)

Ring coupling κ — fraction of bus power tapped into the ring each pass; also sets the resonance linewidth (Q factor).
Wavelength λ — sweep it across a resonance to watch the through-power collapse and the ring glow brighten with circulating power.
Phase shift Δφ — an electrode over one Mach-Zehnder arm changes its refractive index (like applying a voltage), rotating the interference at the output coupler from fully constructive (bar port) to fully destructive (cross port) — this is how a real photonic modulator writes data onto light.

Bus waveguide Ring resonator Phase-shifter arm Output ports

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