arXiv subjects

Hugo Quard

Publications and source records attributed to Hugo Quard.

5 recordsLinked to original sources

arXiv2026

Twist-Reconfigurable van der Waals Moir\'e Photonic Crystals

Moir\'e photonics has emerged as a fascinating concept to design and in situ control of the optical bands. Moir\'e enabled light localisation arises from the relative twist between periodic layers, rather than from fixed, pre-fabricated cavity features. So far, however, the realisation of practical moir\'e photonic crystals in the visible range has been elusive, due to challenges in engineering nanoscale structures and twisting them dynamically post fabrication. Here, we realise a mechanically reconfigurable moir\'e photonic crystal, comprising from two patterned van der Waals crystals (tungsten di sulphide, WS$_2$) slabs separated by an optically active hexagonal boron nitride (hBN) spacer. We reconfigured the same pair of WS$_2$ slabs from a twist angle of 3.8{\deg} to 8.4{\deg} and reconstructed their three-dimensional dispersion using momentum-resolved reflectivity spectroscopy. Further, by reducing the twist angle between the slabs, we observe a denser manifold of folded and hybridised resonances that coincides with a 30-fold enhancement of emission from embedded colour centres. Our results open exciting opportunities for in-situ dispersion engineering and programmable light matter interactions employing van der Waals nanostructures.

physics.optics↗

arXiv2026

Pulsed coherent spectroscopy of a quantum emitter in hexagonal Boron Nitride

Defects in solid-state systems constitute a promising platform for the realization of deterministic quantum emitters. Among many candidate materials and emitters, point defects in hexagonal Boron Nitride (hBN) have recently emerged as particularly promising. In this work, we probe the coherence of an individual B center with a zero phonon line at 436 nm, under pulsed resonant excitation. We observe power-dependent Rabi oscillations up to 5{\pi}, demonstrating optical coherent control of the transition. We achieve an excellent single photon purity of 93% at {\pi}-pulse. Furthermore, we probe the coherence of the two-level system using Ramsey interferometry, revealing an inhomogeneous coherence time of T_2*=0.60 ns. These results establish B centers in hBN as viable candidates for triggered, coherent quantum emitters and represent an important step towards their integration into quantum photonic platforms.

quant-ph↗

arXiv2026

Engineering and Tuning of high quality hexagonal boron nitride nanophotonic resonators

Van der Waals materials are offering intriguing opportunities as building blocks for advanced quantum information technologies and integrated quantum photonic systems. Critical to their development, is robust and high quality light-matter interactions which can be delivered through the fabrication of optical resonators. Here we demonstrate a robust fabrication of one dimensional photonic crystal cavities (1D PCC) and microdisk resonators from hexagonal boron nitride, exhibiting Quality factors of ~ 4300 and ~ 8300, respectively. With these two classes of devices we demonstrated cavity mode tuning via atomic layer deposition and gas condensation. Cavity resonances were shifted by and ~9 nm for the 1D PCCs and ~16 nm in the microdisk resonators, respectively. Our work opening a promising pathway for a realisation emitter cavity coupling in hBN and eventually to a fully integrated quantum photonic circuitry with hBN.

physics.optics↗

arXiv2025

Visible Integrated Photonics with Tantalum Pentoxide

Developing chip-scale photonic platforms for the visible spectrum is essential for translating next-generation optical technologies. Here, we demonstrate that tantalum pentoxide Ta2O5 on insulator is a highly promising material framework for these applications, supporting high-Q resonator architectures across the visible spectral range. Utilizing routine and scalable thin-film deposition and fabrication methodologies, we realize Ta2O5 waveguide and resonator layouts compatible with photonic integrated circuit (PIC) architectures. Through a comparison with numerical simulations, we characterise compact racetrack resonators, evaluating their performance in both the green and blue spectral regions. In addition, we fabricate large-scale ring resonators exhibiting record-high quality factors for Ta2O5 in the visible spectrum, exceeding 7.0 x 10^4. These results highlight the immense potential of this platform for visible photonic systems and establish a robust, straightforward baseline for future visible integrated optics.

physics.optics↗

arXiv2023

Femtosecond laser induced creation of G and W-centers in silicon-on-insulator substrates

The creation of fluorescent defects in silicon is a key stepping stone towards assuring the integration perspectives of quantum photonic devices into existing technologies. Here we demonstrate the creation, by femtosecond laser annealing, of W and G-centers in commercial silicon on insulator (SOI) previously implanted with 12C+ ions. Their quality is comparable to that found for the same emitters obtained with conventional implant processes; as quantified by the photoluminescence radiative lifetime, the broadening of their zero-phonon line (ZPL) and the evolution of these quantities with temperature. In addition to this, we show that both defects can be created without carbon implantation and that we can erase the G-centers by annealing while enhancing the W-centers' emission. These demonstrations are relevant to the deterministic and operando generation of quantum emitters in silicon.

physics.optics↗