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Boyang Nan

Publications and source records attributed to Boyang Nan.

4 recordsLinked to original sources
arXiv2025

High-Q Lithium Niobate Microring Resonator with Electro-Optically Reconfigurable Coupling Strength

The development of sophisticated integrated photonic circuits demands microresonators that combine exceptional optical confinement with dynamic operational flexibility. Here, we demonstrate a racetrack resonator on the thin-film lithium niobate platform that achieves an electro-optically tunable coupling strength while maintaining a stable, high intrinsic Q factor on the order of 10^6. By incorporating a Mach-Zehnder interferometer into the coupling region, the device facilitates a continuous and reversible transition across the entire coupling spectrum from under-coupling and critical coupling to deep over-coupling. To ensure high spectral purity, we employ Euler bends to facilitate an adiabatic transition between the straight and curved waveguide sections. This design effectively suppresses the excitation of higher-order modes, resulting in a clean transmission spectrum characterized by exclusive fundamental mode operation. At the critical coupling point, the resonator exhibits a high extinction ratio exceeding 30 dB. The integration of stable ultra-high Q, single-mode purity, and full-range coupling reconfigurability positions this device as a vital component for adaptive microwave photonics, high-efficiency nonlinear optics, and programmable quantum photonic networks.

physics.optics↗
arXiv2025

Near-Zero Crosstalk and Ultra-Low Loss Waveguide Crossings Enabled by three-dimensional Ta2O5-on-LNOI Integrated Photonic Platform

Waveguide crossings represent one of the most critical components in very-large-scale photonic integration (VLSPI). Three-dimensional waveguide crossings, which distribute optical pathways across multiple planes, can achieve near-zero crosstalk and extremely low crossing-induced loss. However, they face an intrinsic trade-off between interlayer crossing performance and coupling efficiency. To address this challenge, we developed a low-cost fabrication method for 3D waveguide crossings by exploiting the edge rounding effect inherent to chemical mechanical polishing (CMP). Using this method, we demonstrate waveguide crossings with average loss below 0.002 dB and crosstalk below -62 dB on Ta2O5-on-LNOI integrated photonic platform. Our method maintains full compatibility with conventional semiconductor manufacturing technology and paves the way for realizing VLSPI on the thin-film lithium niobate platform.

physics.optics↗
arXiv2025

Monolithically Integrated Optical Convolutional Processors on Thin Film Lithium Niobate

Photonic neural networks (PNNs) of sufficiently large physical dimensions and high operation accuracies are envisaged as an ideal candidate for breaking the major bottlenecks in the current artificial intelligence architectures in terms of latency, energy efficiency and computational power. To achieve this vision, it is of vital importance to scale up the PNNs and in the meantime reduce the high demand on the dimensions required by the PNNs. The underlying cause of this strategy is the enormous gap between the scales of photonic and electronic integrated circuits. Here, we demonstrate monolithically integrated optical convolutional processors on thin film lithium niobate (TFLN) to enable large-scale programmable convolution kernels and in turn greatly reduce the dimensions required by the subsequent fully connected layers. Experimental validation achieves high classification accuracies of 96%/86% on the MNIST/Fashion-MNIST datasets and 84.6% on the AG News dataset, while dramatically reducing the required subsequent fully connected layer dimensions to 196x10 (from 784x10) and 175x4 (from 800x4), respectively. Furthermore, our devices can be driven by commercial field-programmable gate array (FPGA) systems, a unique advantage in addition to their scalable channel number and kernel size, our architecture provides a solution to build practical machine learning photonic devices.

physics.optics↗