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arXiv:2605.29596

Giant Photon Superbunching from Weak Nonlinearity

You Wang, Xu Zheng, Timothy C. H. Liew, Y. D. Chong

physics.opticscond-mat.mes-hallquant-phSubmitted May 28, 2026• Announced May 29, 2026• 0 citations
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Abstract

Photon superbunching, which occurs when the second-order correlation satisfies $g^{(2)}> 2$, is typically associated with strong optical nonlinearities or collective multi-photon emission processes. We predict that extreme superbunching can also arise in systems of weakly-nonlinear photonic cavities, via the creation of a squeezed vacuum through interference engineering by fine-tuning inter-cavity couplings and drive parameters. We present numerical calculations indicating that a system of four photonic resonators containing representative Kerr media can achieve $g^{(2)}(0) = 135$ with a $80\,\text{kHz}$ emission rate. Unlike earlier superbunching schemes, this mechanism is highly compatible with integrated photonic platforms constructed using conventional optical media.

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Photon superbunching, which occurs when the second-order correlation satisfies g(2)>2g^{(2)}> 2g(2)>2, is typically associated with strong optical nonlinearities or collective multi-photon emission processes. We predict that extreme superbunching can also arise in systems of weakly-nonlinear photonic cavities, via the creation of a squeezed vacuum through interference engineering by fine-tuning inter-cavity couplings and drive parameters. We present numerical calculations indicating that a system of four photonic resonators containing representative Kerr media can achieve g(2)(0)=135g^{(2)}(0) = 135g(2)(0)=135 with a 80 kHz80\,\text{kHz}80kHz emission rate. Unlike earlier superbunching schemes, this mechanism is highly compatible with integrated photonic platforms constructed using conventional optical media.
Abstract Photon superbunching, with second-order coherence far beyond the Gaussian thermal limit, is a valuable resource for quantum optics and correlation-based imaging. However, existing sources often rely on fragile platforms, inefficient nonlinear conversion, or mechanically complex architectures. Here, we demonstrate the first highly stable, fully fiber-integrated superbunched random fiber laser that provides a broadly tunable source of giant photon bunching. We establish a cooperative linear–nonlinear mechanism in which Rayleigh-scattering-mediated diffusion provides distributed random feedback, while cascaded stimulated Brillouin scattering and quasi-phase-matched four-wave mixing amplify and redistribute stochastic intensity fluctuations across a spectral comb. This enables continuous tuning of g (2) (0) from approximately 1 to 28 via tailored modulation of linear diffusion strength and nonlinear coupling magnitude. Moreover, by combining photon-correlation measurements with Parisi-overlap analysis, we reveal an inverse correlation between disorder-induced photonic phase evolution and microscopic photon bunching, bridging macroscopic disordered-cavity dynamics and high-order photon statistics. Furthermore, we demonstrate that strongly superbunched light enables temporal ghost imaging with comparable reconstruction fidelity while requiring more than an order-of-magnitude fewer realizations than weakly bunched light. Together, these results establish a fiber-integrated route to engineering giant photon superbunching and high-order light statistics for correlation-based photonic technologies.
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A significantly low value of the single-photon coupling constant is a major challenge in the creation of a single-photon source via photon blockade. Here, we propose a photon blockade scheme composed of a weakly second-order nonlinear medium with an optical parametric amplification in a low-frequency cavity. Unlike the traditional weakly coupled system, the effective coupling strength in the proposed scheme can be significantly higher than the decay rate of the cavity mode. This can be achieved by adjusting the squeezing parameter even if the original coupling strength is weak. The thermal noise of the squeezed cavity mode can be suppressed by a squeezed vacuum field. Using a probability amplitude method, we obtain the optimal condition of photon blockade in the steady-state. By solving the master equation numerically in the steady-state, a strong photon antibunching effect that is consistent with the optimal conditions can be obtained in the cavity with low frequency. Besides, the photon blockade phenomenon and cross-correlation of two cavities can be significantly enhanced under a specific squeezing parameter. Our results may be useful for future studies on the characteristics of photon statistics.
The photon blockade based on weak nonlinearities is called the unconventional photon blockade. The study of the unconventional photon blockade in recent decades has mainly focused on the ${\ensuremath{\chi}}^{(3)}$ Kerr nonlinearity. In this paper, we study the photon blockade in two weakly coupled nonlinear cavities via ${\ensuremath{\chi}}^{(2)}$ nonlinearity, where ${\ensuremath{\chi}}^{(2)}$ mediates the conversion of a single photon in the cavity with high frequency into two photons with low frequency in another cavity. When the two cavity modes are driven simultaneously, our calculations show that the strong photon antibunching can be obtained in the cavity. The optimal condition for strong antibunching is found by analytic calculations and numerical simulations, and discussions of the optimal condition are presented. The differences between the present scheme and that with ${\ensuremath{\chi}}^{(3)}$ nonlinearity are discussed. This scheme is not sensitive to the change of decay rates, which makes the experimental realization easy.
Accessing complete information about the emission from any quantum-optical systems requires tools capable of a frequency-resolved characterization of multi-photon transitions that would go beyond the standard g(2) correlation measurements. This is particularly important when analyzing systems which exhibit strong nonlinear response with multiple emission pathways. In this work, we calculate and analyze in details correlations of light emitted from two such canonical nonlinear optical systems, one incorporating Kerr nonlinear medium, and another exhibiting optomechanical coupling between light and quantized motion of a generic mechanical oscillator. We compare their single- and two-photon emission characteristics by employing a recently developed framework that allows us to calculate the frequency-resolved g(2) correlations between emitted photons with two arbitrary frequencies. Our analysis shows a rich landscape of bunching and antibunching associated with multi-photon emission events, and reveals the distinctive temporal characteristics of such processes. This new understanding provides a new asset to characterize and exploit nonlinear phenomena in Kerr and optomechanical systems in future experiments.
Achieving the regime of single-photon nonlinearities in photonic devices by just exploiting the intrinsic high-order susceptibilities of conventional materials would open the door to practical semiconductor-based quantum photonic technologies. Here we show that this regime can be achieved in a triply resonant integrated photonic device made of two coupled ring resonators, in a material platform displaying an intrinsic third-order nonlinearity. By strongly driving one of the three resonances of the system, a weak coherent probe at one of the others results in a strongly suppressed two-photon probability at the output, evidenced by an antibunched second-order correlation function at zero-time delay under continuous wave driving.