Electrically switchable photonic diode empowered by chiral resonance

Abstract

The on-chip integration of nonreciprocal optical devices remains a critical challenge for modern optoelectronics, as conventional magneto-optic approaches suffer from material incompatibility and excessive optical losses. Nonlinear photonic diodes have emerged as a promising magnet-free alternative, yet their widespread adoption has been constrained by inherent limitations in reconfigurability. Here, we present an all-silicon, electrically tunable photonic diode leveraging engineered chiral resonances in an ultra-compact microring architecture. The pronounced asymmetric modal coupling enables nonreciprocal transmission with two distinct operation modes at threshold powers down to -5 dBm. The chirality further enables unprecedented control over self-pulsation dynamics, manifesting in propagation-direction-dependent oscillation thresholds and temporal signatures. Crucially, post-fabrication electrical reconfigurability allows dynamic switching between forward, backward, and disabled states. This work represents a significant advancement in integrated nonreciprocal photonics, offering a CMOS-compatible solution with transformative potential for optical interconnects, photonic neural networks, and signal processing systems.

Figures (5)

• Figure 1: Nonreciprocity in a chirality-enabled photonic diode.a, Schematic of a waveguide-coupled spiral ring on an SOI platform operating as an integrated photonic diode in the forward state ($\alpha < 0$), in which backward transmission is prohibited. The integrated phase shifter enables electrical control of mode chirality. b, Numerically calculated mode chirality $\alpha$ as a function of $\theta$ without (black) and with (brown) electrical tuning. c, Schematic of transmission responses in the linear and nonlinear regimes. The blocking ratio $\Gamma_\text{BLO}$ is defined as the highest achievable transmission contrast within the non-reciprocal band. d, Transmission contrast $\Delta Tr = Tr_{1} - Tr_{2}$ as a function of wavelength, with highlighted reconfigurable non-reciprocal band (shaded areas) in the forward (top) and backward (bottom) states. e, Schematic showing the evolution of the non-reciprocal bandwidth $\Delta \lambda_\text{NR}$ on the injection power $P_\text{in}$ upon tailorable mode chirality, in which three different operational states are denoted. The threshold power $P_\text{th}$ is defined as the required injection power to achieve $\Gamma_\text{BLO}$ of $3\,\mathrm{dB}$.
• Figure 2: Characterization of mode chirality through backscattering and interferometric spectra.a, Optical microscope image of a waveguide-coupled spiral ring resonator with radius $R$ of $5\,\mu \mathrm{m}$, $\theta = 122.4^\circ$ and deformation parameter $\epsilon = 0.013$. b, Measured transmission spectra $Tr_{1}$ and $Tr_{2}$ (top) and backreflection spectra $R_1$ and $R_2$ (bottom) under single-port excitation. The on-chip injection power $P_\text{in}$ was defined as the optical power coupled into the bus waveguide after the grating coupler. Here the estimated $P_\text{in}$ is $-11\,\mathrm{dBm}$. c, Transmission spectra $Tr_{1}$ and $Tr_{2}$ (top) under simultaneous dual-port excitation. d, Modeled evolution of transmission spectrum $Tr_{1}$ under dual-port excitation with the relative phase delay $\Phi$ between the two inputs.
• Figure 3: Characterization of non-reciprocal transmission in two distinct operation modes.a, Thermal equilibrium diagram illustrating cavity temperature $T$ versus the probe wavelength for two states. The green curve denotes the transmission spectrum of the cold cavity. The cold resonant regime and bistable regime are denoted with the orange and purple shaded areas, respectively. b, Optical bistability of the system characterized by two transmission spectra $Tr_{2}$ under different laser scanning conditions. c-d, Measured transmission spectra $Tr_{1}$ and $Tr_{r}$ for the pre-activated (c) and the independent mode (d), with increasing $P_\text{in}$. The shaded areas represent the non-reciprocal band. e, Summarized evolutions of the relative resonance wavelength offset (left) and $\Gamma_\text{BLO}$ (right) as a function of $P_\text{in}$ for two operation modes. $P_\text{th}$ is denoted with gray dashed lines.
• Figure 4: Chirality-mediated SP dynamics.a--b, Maps of SP frequency $\omega_\text{SP}$ as functions of the probe wavelength $\lambda_p$ and the input power $P_\text{in}$ for backward (a) and forward (b) injection performed in the pre-activated mode. c, Measured temporal waveform upon $P_\text{in}$ of $-2\,\mathrm{dBm}$ (left) and $4\,\mathrm{dBm}$ (right) for backward injection. d, Modeled temporal responses for (c). e, Phase diagram showing the trace of $\Delta N$--$\Delta T$ trajectories for two injection directions, with arrows indicating thermodynamic phase progression. f--g, Maps of $\omega_\text{SP}$ as functions of $\lambda_p$ and $P_\text{in}$ for backward (f) and forward (g) injection performed in the independent mode. h, Phase diagram showing the trace of $\Delta N$--$\Delta T$ trajectories upon backward injection in both operation modes.
• Figure 5: Demonstration of an electrically switchable photonic diode.a, Summarized evolution of backreflection spectra $R_1$ and $R_2$ upon varying $P_\text{elec}$ from $0\,\mathrm{mW}$ to $80\,\mathrm{mW}$, measured at $P_\text{in} = -13\,\mathrm{dBm}$. b, Extracted mode chirality as a function of $P_\text{elec}$. c, Summarized evolution of $\Delta T_r$ upon varying $P_\text{elec}$ from $0\,\mathrm{mW}$ to $80\,\mathrm{mW}$, measured at $P_\text{in} = -1\,\mathrm{dBm}$. d, Summarized evolution of $\Delta \lambda_\text{NR}$ on the injection power $P_\text{in}$ for three representative $P_\text{elec}$ of $20\,\mathrm{mW}$, $40\,\mathrm{mW}$, and $70\,\mathrm{mW}$.