arXiv subjects

San Lam Ng

Publications and source records attributed to San Lam Ng.

3 recordsLinked to original sources

arXiv2026

Electrically Reconfigurable Silicon Carbide Nanophotonic Cavities on Thin-Film Lithium Niobate

Interfacing integrated photonics with solid-state spin defects holds great promise for future quantum networks, but the scaling of spin-photon architectures is hindered by frequency mismatches arising from fabrication-induced variations in photonic cavity resonances and the inhomogeneous optical transition frequencies of individual spins. These challenges call for a photonic platform with deterministic and wide-range tunability. Here, we demonstrate a hybrid nanophotonic platform based on direct bonding of silicon carbide photonic crystal nanocavity arrays onto thin-film lithium niobate on insulator, enabling deterministic electrical tuning of multiple SiC nanocavities into mutual spectral resonance. By exploiting the strong electro-optic response of lithium niobate, we achieve continuous and wide-range cavity tuning of 380 GHz ($\sim$1.1 nm), sufficient to compensate both cavity disorder and spin inhomogeneity. The nanocavities balance strong optical confinement with electrical tunability, exhibiting a theoretical Purcell factor of approximately 400. This hybrid platform enables electrically reconfigurable spin-photon interfaces for large-scale integrated quantum photonics.

physics.optics↗

arXiv2025

Deformation-Driven Enhancement of Spin Defect Emission in Hexagonal Boron Nitride

The negatively charged boron vacancy (VB-) in hexagonal boron nitride (hBN) has been extensively investigated as it offers a novel playground for two-dimensional quantum sensing, with ultimate proximity to target samples. However, its practical sensitivity is limited by the intrinsically weak photoluminescence of the spin ensemble. Here, we report a photoluminescence enhancement of up to 30 times from VB- centers in suspended regions of hBN compared to those in substrate-supported areas. The key spin properties, such as the optically detected magnetic resonance (ODMR) contrast and linewidth, as well as the spin lifetime, of the VB- centers in this region are well preserved. Detailed investigations, including measurements of zero-field ODMR, Raman spectroscopy, and Kelvin probe force microscopy, reveal a correlation between emission enhancement and local deformation in the sample. It is concluded that the suspended regions exhibit higher local deformation compared to the supported areas, breaking the local symmetry and thereby activating otherwise forbidden or weak optical transitions of the VB- centers.

quant-ph↗

arXiv2022

Microscopic study of optically-stable, coherent color centers in diamond generated by high-temperature annealing

Single color centers in solid have emerged as promising physical platforms for quantum information science. Creating these centers with excellent quantum properties is a key foundation for further technological developments. In particular, the microscopic understanding of the spin bath environments is the key to engineer color centers for quantum control. In this work, we propose and demonstrate a distinct high-temperature annealing (HTA) approach for creating high-quality nitrogen vacancy (NV) centers in implantation-free diamonds. Simultaneously using the created NV centers as probes for their local environment we verify that no damage was microscopically induced by the HTA. Nearly all single NV centers created in ultra-low-nitrogen-concentration membranes possess stable and Fourier-transform-limited optical spectra. Furthermore, HTA strongly reduces noise sources naturally grown in ensemble samples, and leads to more than three-fold improvements of decoherence time and sensitivity. We also verify that the vacancy activation and defect reformation, especially H3 and P1 centers, can explain the reconfiguration between spin baths and color centers. This novel approach will become a powerful tool in vacancy-based quantum technology.

cond-mat.mes-hall↗