Searcharxiv⌕ Search
Home/Archive/arXiv

arXiv · 2610.03560

Beyond the PT-Broken Phase: Constant-Frequency Oscillation from Floquet Hybridization

Xiaoke Gao·Xiaoyin Sha·Xunyan Sun·Xianglin Hao·Huaiqing Zhang·Tianyu Dong
View original source ↗Read source document ↗Export metadata ↓

Abstract

Constant-frequency oscillation is usually tied to the broken phase of a spatially coupled PT-symmetric dimer, where the eigenfrequencies form a complex-conjugate pair with a fixed real part. This work shows that an analogous locking can instead come from Floquet hybridization in a synthetic frequency dimension. Periodic gain--loss modulation folds the spectrum into replicas spaced by the drive frequency $Ω$. Coupling between neighboring replicas opens an additional real-part degeneracy at the edge of the Floquet Brillouin zone. The hybridized Floquet mode at $ω_0\pmΩ/2$ requires the minimum gain and is therefore selected for the self-oscillation. A Floquet PT-symmetric circuit with a JFET time-varying negative resistance confirms the prediction. The observed constant-frequency oscillation contains two frequency components of comparable amplitude, separated by the modulation frequency, which identifies its origin from Floquet hybridization rather than ordinary PT-symmetry breaking or dispersion flattening. More broadly, once a suitably symmetry-constrained spectral degeneracy is established, self-sustained frequency pinning can arise beyond the conventional spatial PT-broken phase.

Explore related subjects

physics.opticsphysics.app-ph

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Xiaoke Gao, Xiaoyin Sha, Xunyan Sun, Xianglin Hao, Huaiqing Zhang, Tianyu Dong. 2026-10-02. Beyond the PT-Broken Phase: Constant-Frequency Oscillation from Floquet Hybridization. https://arxiv.org/abs/2610.03560

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Vectorial Control of Scintillation in Kolmogorov Turbulence and Quality Parametrization

Intensity scintillation limits free-space optical links in strong turbulence. We examine experimentally how sequential linear polarization filtering modifies the scintillation of a laser beam distorted by Kolmogorov-type turbulence, and interpret the results with a vector-field and fourth-order-moment model. A collimated He--Ne beam (632.8~nm) crossed a rotating pseudo-random phase plate (Fried parameter $r_0\approx0.6$~mm) and zero to five co-aligned thin-film polarizers; 200 camera frames were recorded per configuration, together with a turbulence-free reference. For fully developed speckle the model gives a total-field index $σ_I^2=(1+P^2)/2$ in terms of the degree of polarization $P$. From zero to five polarizers, the Gaussian-envelope scintillation index fell from 0.083 to 0.002 and the single-pixel index from 0.80 to 0.27 (about 66\%), whereas beam wander remained comparable across configurations. As Gaussian statistics alone cannot explain this reduction, we attribute it to rejection of a depolarized, strongly fluctuating component and derive a quantitative criterion for this mechanism. Passive polarization filtering thus offers a simple, low-cost route to scintillation mitigation in free-space optical terminals.

physics.optics↗
arXiv2026

Constraints on the Origin of Universal $1/f^2$ Photon-Count Spectra at Baseband

A series of 11.6-d-duration photon-counting experiments, employing a broad variety of light sources with different statistical properties and optical spectra, were carried out over a 1.5-yr period. All of the photon-count spectra at baseband followed a common $1/f^2$ form over the frequency range $1 \times 10^{-6} \leqslant f \leqslant 5 \times 10^{-4}$ Hz, corresponding to a timescale range $33$ min $ \leqslant T_f \leqslant 11.6$ d, where $T_f \equiv 1/f$. The lower and upper timescale limits were established by the photodetector noise floor and the duration of the individual experiments, respectively. Unlike ordinary Brownian motion, all of the measured photon-count sample paths exhibited irregular long-timescale fluctuations, with durations ranging from hours to days. It has been established that the photon-count spectra cannot plausibly be ascribed to fluctuations of the current, voltage, or temperature of the source or the detector, nor to technical sources of noise associated with the optical system or local environment. Although the physical origin of the photon-count fluctuations remains unresolved, several heterodox hypotheses are set forth. From a statistical point-of-view, the photon counts appear to follow a doubly stochastic Poisson process with a slowly varying random intensity. Analogous experiments that rely on ionizing radiation and direct-conversion solid-state radiation detectors are proposed.

physics.optics↗
arXiv2026

Scatter-free perfect reflection in multichannel monolithic high-contrast gratings: direct--indirect Fourier-harmonic interference and dimensionality of the solution set

Monolithic high-contrast gratings (MHCGs) can exhibit scatter-free perfect reflection despite open higher-order substrate diffraction channels, but the underlying mechanism has not been fully clarified. Using a Fourier-harmonic description, we show that all open higher-order channels in the high-index substrate can be simultaneously extinguished through destructive interference between the radiation fields generated by the direct and indirect source contributions. By contrast, the zeroth-order transmission vanishes when the modulation-induced zeroth-order field interferes destructively with the background transmitted field of the incident wave. Together, these cancellations yield unit zeroth-order reflectance in lossless MHCGs. The near invariance of the internal field harmonics accounts for the remarkable stability of these conditions against changes in the substrate refractive index. We further show that the number of symmetry-compatible open channels determines the generic codimension of the perfect-reflection solution set. Depending on the number of independent design parameters relative to this codimension, the solutions form continuous curves, appear as isolated points, or are generically absent. Introducing an additional geometrical parameter restores isolated perfect-reflection solutions when an additional diffraction channel opens. The same cancellation mechanisms and channel counting apply to both TE and TM polarizations.

physics.optics↗