arXiv subjects

Bingrui Lu

Publications and source records attributed to Bingrui Lu.

4 recordsLinked to original sources

arXiv2026

Broadband silicon photonic phase shifters driven by gradient optical forces

While initially deployed for optical interconnects, silicon photonics is increasingly being explored as a hardware platform for programmable optical systems, including linear optical processors, neuromorphic photonic networks, quantum photonic circuits and multiplexed sensor arrays. Common to most existing implementations is that light is controlled with electronics, and even basic demonstrations wherein light directly controls light remain limited. Here we demonstrate a broadband all-optical silicon photonic phase shifter based on an optomechanically mediated light-light interaction arising from the gradient optical force. Our device concept relies on slot-mode waveguides suspended by subwavelength gratings, which provide mechanical support while preserving optical confinement. We demonstrate all-optical phase shifting using a guided pump beam co-propagating with the signal beam, with only 60 $\mu$W required to achieve a $\pi$ phase shift in a 178.6 $\mu$m-long device. In addition, we measure the required pump power across a wide parameter space and find quantitative agreement with a lumped force-equilibrium model. Since the actuation relies on an all-optical geometric deformation rather than on material-index tuning, the approach avoids local electrical connections to the active element, carries no Kramers-Kronig absorption penalty, and is naturally compatible with cryogenic quantum photonic platforms.

physics.optics↗

arXiv2026

Coupled Flexural Optomechanical Cavities with Engineered Nanomechanical Interconnects

Integrated nanomechanical circuits require compact and predictable ways to read out, confine, and connect mechanical motion across multiple nanoscale elements. This challenge is particularly acute for megahertz flexural modes, whose large mechanical response and nonlinear dynamics are attractive for optomechanics, sensing, and signal processing, but whose extended nature makes local confinement and coupling difficult within dense devices. Here we demonstrate an optomechanical nanobeam platform in which optical transduction and mechanical connectivity are both engineered lithographically. Transverse geometric asymmetry in the photonic-crystal cavity breaks the cancellation that suppresses dispersive coupling to in-plane flexural motion, making these modes optically bright without ancillary structures. In parallel, serpentine mechanical links engineered through their complex band structure act as compact mirrors and evanescent couplers for MHz flexural waves. In coupled-cavity devices, the normal-mode splitting decays exponentially with the number of serpentine cells, yielding an experimental attenuation constant in quantitative agreement with full-system simulations. Geometry-dependent measurements further show that the coupling can be tuned by the interconnect design and identify regimes where finite-link modes hybridize with the cavity modes, beyond a simple two-resonator picture. These results establish complex-band-engineered mechanical links as calibrated interconnects for scalable optomechanical nanocircuits based on optically addressable MHz flexural resonators.

physics.optics↗

arXiv2026

Computing with the complex nonlinear dynamics of an optomechanical oscillator

An optomechanical oscillator undergoes a Hopf bifurcation that connects two dynamical regimes with different information-processing capabilities: thermal Brownian motion and coherent self-sustained oscillation. Below threshold, the oscillator occupies a stable fixed point around which thermal fluctuations drive stochastic Brownian motion - a regime dominated by linear response, with only short-lived memory and negligible usable nonlinearity. Above threshold, radiation pressure, free-carrier dynamics, and thermo-optic relaxation act together to sustain a stable limit cycle that simultaneously provides both nonlinear transformation and dynamical memory. Here we show that this coherent regime can be used as a physical reservoir for computation: by perturbing the phonon-lasing attractor, the cavity performs nonlinear input-output transformations and retains short-term memory without any external feedback mechanism. Using only a single chip-integrated device with 20 virtual nodes, we reconstruct nonlinear functions, predict the evolution of chaotic time series, and perform spoken digit classification on a two-digit sub-task. The mechanical resonance frequency sets the intrinsic dynamical timescale of the reservoir and therefore its processing speed; while the present device operates near 0.4 GHz, optomechanical and nanomechanical systems can be engineered to reach multi-GHz and sub-terahertz frequencies, directly translating into a scalable path toward ultrafast integrated physical computing.

physics.optics↗

arXiv2025

Nanoelectromechanical spectral control of silicon bowtie nanocavities for quantum light sources

We present the design, fabrication, and characterization of tunable waveguide-coupled silicon bowtie cavities with strong spatial electromagnetic field confinement. We use nanoelectromechanical in-plane actuation for the tuning, as this combines cryocompatibility with an ultralow power consumption. Our device leverages a mode volume below 0.2 cubic wavelengths in the material to reach theoretical Purcell factors above 6,500 and waveguide-coupling efficiency above 30% across the full experimentally measured spectral-tuning range of 11 nm. Notably, the Purcell factor in our cavity depends only weakly on the applied voltage. Our spectral measurements demonstrate reversible tuning of bowtie cavities, and we directly show the in-plane actuation using in-situ characterization in a scanning electron microscope. Our results constitute the first demonstration of a low-loss dielectric tunable bowtie nanocavity with strong light confinement. This solves a key issue for experiments on strong light-matter interactions for cavity quantum electrodynamics and scalable photonic quantum technologies.

physics.optics↗