Strong Nonlinear Coupling in a ${\mathrm{Si}}_3{\mathrm{N}}_4$ Ring Resonator

We demonstrate that nondegenerate four-wave mixing in a ${\mathrm{Si}}_3{\mathrm{N}}_4$ microring resonator can result in a nonlinear coupling rate between two optical fields exceeding their energy dissipation rate in the resonator, corresponding to strong nonlinear coupling. We demonstrate that this leads to a Rabi-like splitting, for which we provide a theoretical description in agreement with our experimental results. This yields new insight into the dynamics of nonlinear optical interactions in microresonators and access to novel phenomena.

Figure 1

FWM process driven by a strong field at ${\omega }_P$ (a) can be modeled as a time-dependent effective second-order nonlinear interaction leading to the generation of the idler field. (b). Sketch of the FWM process in a single-bus waveguide ring resonator (c).

Figure 2

(a) Schematics of the experiment. EDFA, erbium doped fiber amplifier; WDM, wave division multiplexing; LPF, low-pass filter; PD photodiode, SSPD superconducting single-photon detectors. The centers of the WDM channel and threshold of the LPF are 1592, 1405, and 1250 nm, respectively. (b) Microscope image of part of the microresonator chip. The sample detail shows three different resonators, and the lensed fiber for input-output coupling on the right side of the chip.

Figure 3

Idler generation as a function of seed power. The main plot shows the inferred on-chip conversion efficiency as a function of seed power. The inset shows a double-logarithmic plot of the idler power vs seed power, where the dashed line is a trend curve that highlights the linear scaling between seed powers of about $0.1\mu \mathrm{W}$, where the idler power arises above noise, to seed powers of about $10\mu \mathrm{W}$, where saturation effects begin to be important. The shaded region indicates the theoretical expected trend within the estimated errors.

Figure 4

Seed (green) transmission and idler (blue) generation when seed wavelength is scanned across the resonance. On the left, the seed power $P_{\mathrm{seed}}=20\mu \mathrm{W}$. On the right, where $P_{\mathrm{seed}}=300\mu \mathrm{W}$, the profiles are modified by the strong nonlinear coupling.

Figure 5

Seed transmission as the seed wavelength is scanned across the seed resonance for different seed input power levels. A characteristic change of the resonance shape appears for higher seed power.