arXiv subjects

Haoran Ren

Publications and source records attributed to Haoran Ren.

At least 19 recordsLinked to original sources

arXiv2026

Quantum skyrmion parallelism via metasurface-tailored high-dimensional entanglement

Quantum skyrmions are topological structures that have garnered significant interest due to their demonstrated robustness and versatility across diverse optical platforms. However, existing approaches for their generation are limited to producing pre-determined two dimensional qubit states with a single topology. Here we create multi-dimensional topological states by introducing a non-local interaction between high-dimensional photonic entanglement and a metasurface, where the topological transformation induced by the metasurface is made non-deterministic by the probabilistic nature of the interfacing entangled state. Within this framework, we demonstrate that individual quantum states can host multiple co-existing topologies that are only revealed upon measurement, allowing for their parallel transport within distinct spatial mode channels. We confirm this by revealing the rich topological landscape within our modified Hilbert space while controlling the desired output topology by orbital angular momentum (OAM) projections on one of the entangled photons, producing multiple non-local polarization-OAM entangled states characterized by distinct topological classes, all from a single metasurface device. Our results reveal new capability when structured high-dimensional entanglement is interfaced with structured matter capable of coupling photonic degrees of freedom, establishing a new pathway for the compact generation of complex quantum states.

quant-ph↗

arXiv2026

Metalens stereoscopic optical palpation for imaging cancer mechanics

Accurate intraoperative margin assessment is critical for complete resection of solid tumours. However, surgeons routinely rely on manual palpation, which is highly subjective and fundamentally limited by poor spatial resolution, and pre-operative imaging lacks real-time feedback. While emerging optical elastography techniques offer quantitative mechanical contrast, their reliance on bulky optical components necessitates cumbersome alignment and hinders integration into miniaturised surgical instruments. Here, we report metalens stereoscopic optical palpation (MSOP), a nanophotonic imaging platform leveraging a binocular metalens integrated with a single CMOS sensor to achieve high-fidelity, self-aligned elastography. By replacing complex bulk optics with a compact stereoscopic architecture, MSOP enables robust, high-contrast mapping of tissue surface stress. Following validation in heterogeneous silicone phantoms, we demonstrate MSOP's translational potential by characterising the mechanical signatures of malignancies in fresh mouse pancreatic cancer models, as well as excised human breast and liver specimens. By providing reliable, label-free mechanical contrast across diverse oncological landscapes, MSOP offers a compact tool for precise intraoperative margin delineation to reduce re-excision rates and improve surgical outcomes.

physics.optics↗

arXiv2026

Hybrid Symmetry Breaking for Chiral Quasi-Bound States in the Continuum

Chiral optical modes provide a fundamental platform for spin selective light matter interactions and underpin emerging applications ranging from chiral emission to polarization-controlled photonic devices. They are typically achieved by tailoring specific structural asymmetries to directly induce circularly polarized radiation. Here, we introduce hybrid symmetry breaking as a general route for generating and controlling chiral quasi-bound states in the continuum (qBICs). By combining multiple orthogonal symmetry perturbations, optical chirality emerges in otherwise achiral photonic structures and evolves continuously from linear to circular polarization. A parity based analysis reveals that the chiral qBICs originate from the symmetry-controlled evolution of parity allowed radiative channels. We demonstrate the universality of the approach across multiple BIC platforms, achieve deterministic control of the polarization state across nearly the entire Poincare sphere, and further establish dynamic chirality reconfiguration in a fixed structure through a phase-change material. More broadly, our results demonstrate that optical chirality can emerge from symmetry engineering, providing a general framework for the design of chiral photonic states.

physics.optics↗

arXiv2026

Orbital Angular Momentum Locking via Bound States in the Continuum

Optical vortices are electromagnetic fields twisting around a phase singularity, resulting in quantized orbital angular momentum (OAM). When such vortices are formed by evanescent hybrid light-matter quasiparticles known as polaritons, they are referred to as polaritonic vortices (PVs). The nanometer-scale topologically robust features of such PVs promise to enable applications for lasing and thermal emission at deeply subwavelength scales. However, many conventional techniques are prone to producing multimode PVs due to poor mode selectivity, resulting in OAM mixing that degrades vortex purity and limits their performance for high-fidelity optical information encoding and multi-dimensional imaging. To overcome this limitation, we introduce a platform that generates deeply subwavelength PVs through quasi-bound states in the continuum (qBICs) in dielectric metasurfaces. In contrast to existing approaches, the qBIC intrinsically locks the PV to a single OAM and makes it robust against the polarization state of the excitation, including linear, elliptical and circular polarization. We experimentally realize qBIC-driven PVs through the interference of hyperbolic phonon polaritons (HPhPs) in hexagonal boron nitride by exploiting the highly uniform out-of-plane electric fields generated by the photonic qBIC, characterized via scattering scanning near-field optical microscopy. This results in HPhPs with a wavelength of around 30-40 smaller than the incident light, thereby enabling ultra-dense packing of multiple robust PVs with distinct OAM. Our platform brings PVs to the photonic chip scale, enabling applications in structured optical information transfer and communications.

physics.optics↗

arXiv2025

Disorder-enabled Synthetic Metasurfaces

Optical metasurfaces have catalyzed transformative advances across imaging, optoelectronics, quantum information processing, sensing, energy conversion, and optical computing. Yet, despite this rapid progress, most research remains focused on optimizing single functionalities, constrained by the persistent challenge of integrating multiple functions within a single device. Here, we demonstrate that engineered structural disorder of metapixels, used to implement a photonic function, can significantly reduce the area required across the entire aperture without compromising optical performance. The unallocated space can then be repurposed to encode functionally distinct metapixels without increasing the design complexity, each independently addressable via various optical degrees of freedom. As a proof of concept, we present a synthetic achromatic metalens featuring 11 spectrally distinct lens profiles encoded through nonlocal metapixels engineered to support sharp resonances via quasi bound states in the continuum. This large-scale metalens with 8.1 mm aperture achieves diffraction-limited achromatic focusing across the 1200 to 1400 nm spectral window. We further incorporate polarization-selective metapixels to implement momentum-space distinct gratings, enabling single-shot, high spatial resolution polarimetric imaging of arbitrarily structured light fields, including radial and azimuthal vector beams and optical skyrmions. Altogether, this disorder-enabled synthetic metasurface platform establishes a versatile foundation for unifying diverse photonic functionalities within a single optical element, marking a substantial step toward compact, high-density, multifunctional optical devices.

physics.optics↗

arXiv2025

Resonant helical dichroism in twisted dielectric metastructures

Circular dichroism, arising from interactions with light fields of opposite spin angular momentum, has become a fundamental tool for molecular characterization. Meanwhile, helical dichroism (HD) - the dichroic response to vortex beams carrying opposite orbital angular momentum (OAM) - offers an alternative approach for probing chiral molecules and photonic structures. Previous demonstrations of HD have been limited to non-resonant light-matter interactions with chiral micro- and nanostructures, leaving the realization of resonance helical dichroism largely unexplored. Here, we present the design and implementation of twisted dielectric metastructures, composed of an array of rotated silicon trimer nanostructures harnessing nonlocal photonic modes with a high quality factor of several dozen that enable strong resonant HD for OAM values up to $10$. We experimentally demonstrate resonantly enhanced HD for strongly focused OAM beams with the magnitude of topological charges from $1$ to $3$. Our findings pave the way for resonant nanophotonics involving OAM beams, unlocking the full potential of structured light for applications in molecular sensing, optical imaging, nonlinear optics, and optical data storage.

physics.optics↗

arXiv2025

Compact orbital-angular-momentum multiplexing via laser-written glass chips

Orbital angular momentum (OAM) modes have emerged as a promising solution for enhancing the capacity of optical multiplexing systems, leveraging their theoretically unbounded set of orthogonal spatial modes. However, the generation and detection of OAM multiplexing signals are predominantly reliant on bulky optical components within complex optical setups. We introduce a compact solution for OAM information processing using laser-written glass chips, facilitating efficient multiplexing and demultiplexing of multiple OAM information channels. During the multiplexing process, OAM channels are managed via laser-scribed single-mode waveguides within a glass chip, with their modes converted using laser-written holograms on the side wall of the glass chip. The reverse optical process is employed for OAM demultiplexing. Our chips seamlessly interface with commercial optical fibers, ensuring compatibility with existing fiber-optic communication infrastructure. This work not only establishes a novel approach for OAM optical multiplexing but also underscores the potential of laser-writing technology in advancing photonics and its practical applications in optical communications.

physics.optics↗

arXiv2025

Valley optoelectronics based on meta-waveguide photodetectors

In transition metal dichalcogenides, the valley degree of freedom directly couples valley-polarised excitons - excited by circularly polarised light - to valley-dependent chiral photons, enabling ultrafast light-driven valleytronics. However, achieving fully integrated valley optoelectronics - incorporating on-chip generation, selective routing, and electrical readout of valley-dependent chiral photons - remains an unresolved challenge. We present a valley-driven hybrid nanophotonic-optoelectronic circuit that integrates chirality-selective meta-waveguide photodetectors with transition metal dichalcogenides. At room temperature, our purposely designed meta-waveguide device generates near-unity valley-dependent chiral photons in the second harmonic generation from an encapsulated tungsten disulfide monolayer and selectively couples them to unidirectional waveguide modes, achieving an exceptional polarisation selectivity of 0.97. These valley-dependent waveguide modes were subsequently detected by atomically thin few-layer tungsten diselenide photodetectors, exclusively responsive to the above-bandgap upconverted photons, thereby enabling all-on-chip processing of valley-multiplexed images. Our demonstration bridges a critical gap in lightwave valleytronics, paving the way for compact, scalable valley information processing and fostering the development of light-based valleytronic quantum technologies.

physics.optics↗

arXiv2025

An Inverse Design Wavelength Demultiplexer for On-Chip Photoluminescence Sorting in TMDC Heterostructures

Emerging two-dimensional transition metal dichalcogenides (TMDCs) offer a promising platform for on-chip integrated photonics because of their unique optical and electronic properties. Their naturally passivated surfaces make them highly tolerant to lattice mismatch, enabling seamless heterogeneous integration by stacking different van der Waals materials, a crucial step in the development of advanced photonic devices. Here, we demonstrate the use of an inverse design wavelength demultiplexing waveguides for on-chip sorting and routing of distinct photoluminescence from the heterojunction formed by WS2 and WSe2 monolayers. The integrated nanophotonic chip splits and sorts excitonic emission into individual waveguides at room temperature. Our demonstration opens up new perspectives for integrating light sources in van der Waals materials with functional integrated photonics, offering a versatile platform for both fundamental research and practical applications.

physics.optics↗

arXiv2024

Ultrathin BIC metasurfaces based on ultralow-loss Sb2Se3 phase-change material

Phase-change materials (PCMs) are increasingly recognised as promising platforms for tunable photonic devices due to their ability to modulate optical properties through solid-state phase transitions. Ultrathin and low-loss PCMs are highly valued for their fast and more effective phase transitions and applications in reconfigurable photonic chips, metasurfaces, optical modulators, sensors, photonic memories, and neuromorphic computing. However, conventional PCMs such as GST, GSST, VO2, and In3SbTe2, despite optimisation for tunable meta-optics, suffer from high intrinsic losses in the near-infrared (NIR) region, limiting their potential for high quality factor (Q-factor) resonant metasurfaces. Here we present the design and fabrication of tunable bound states in the continuum (BIC) metasurfaces using the ultralow-loss PCM Sb2Se3. Our BIC metasurfaces, only 25 nm thick, achieve high modulation depth and broad resonance tuning in the NIR with high Q-factors up to 130, without the need for additional materials. Experimentally, we employ these BIC metasurfaces to modulate photoluminescence in rare earth-doped upconversion nanoparticles, reducing the excitation power for multiphoton photoluminescence and enabling emission polarisation manipulation. This work offers a promising platform for developing active resonant metasurfaces in the NIR region, with broad applications including super resolution imaging, optical modulation, ultrafast switches, harmonic generation, colour filtering, and optical sensing.

physics.optics↗

arXiv2024

Ultranarrow-linewidth Wavelength-Vortex Metasurface Holography

Ultrathin metasurface holograms, with thicknesses comparable to the operating wavelength, leverage multiple degrees of freedom of light to address independent image channels, thereby significantly enhancing information capacity. Although the wavelength of light can be used to encode holographic image channels, high-capacity wavelength-multiplexing holography has traditionally been achieved only through 3D volume holograms based on Bragg diffraction. We demonstrate ultranarrow-linewidth wavelength-vortex multiplexing holography in ultrathin metasurface holograms. By applying dispersion engineering to the elementary grating functions of a multiplexing hologram, we develop a sparse k-vector-filtering aperture array in momentum space that achieves sharp wavelength selectivity in conjunction with orbital angular momentum selectivity. Further leveraging transformer neural networks for the design of phase-only multiplexing holograms, we reconstruct up to 118 independent image channels from a single metasurface hologram, achieving an ultranarrow linewidth of 2 nm in the visible range. Finally, we apply the developed wavelength-vortex multiplexing metasurface holograms for holographic visual cryptography, achieving unprecedented security with an information rate more than 2500 times higher than that of traditional visual cryptography schemes. Our results open exciting avenues for the use of metasurface holograms in various applications, including 3D displays, holographic encryption, beam shaping, LiDAR, microscopy, data storage, and optical artificial intelligence.

physics.optics↗

arXiv2023

Arbitrary structured quantum emission with a multifunctional imaging metalens

Structuring light emission from single-photon emitters in multiple degrees of freedom is of a great importance for quantum information processing towards higher dimensions. However, traditional control of emission from quantum light sources relies on the use of multiple bulky optical elements or nanostructured resonators with limited functionalities, constraining the potential of multi-dimensional tailoring. Here we introduce the use of an ultrathin polarisation-beam-splitting metalens for the arbitrary structuring of quantum emission at room temperature. Owing to the complete and independent polarisation and phase control at a single meta-atom level, the designed metalens enables simultaneous imaging of quantum emission from ultra-bright defects in hexagonal boron nitride and imprinting of an arbitrary wavefront onto orthogonal polarisation states of the sources. The hybrid quantum metalens enables simultaneous manipulation of multiple degrees of freedom of a quantum light source, including directionality, polarisation, and orbital angular momentum. The demonstrated arbitrary wavefront shaping of quantum emission in multiple degrees of freedom could unleash the full potential of solid-state SPEs for their use as high-dimensional quantum sources for advanced quantum photonic applications.

physics.optics↗

arXiv2023

Optically addressable spin defects coupled to bound states in the continuum metasurfaces

Van der Waals (vdW) materials, including hexagonal boron nitride (hBN), are layered crystalline solids with appealing properties for investigating light-matter interactions at the nanoscale. hBN has emerged as a versatile building block for nanophotonic structures, and the recent identification of native optically addressable spin defects has opened up exciting possibilities in quantum technologies. However, these defects exhibit relatively low quantum efficiencies and a broad emission spectrum, limiting potential applications. Optical metasurfaces present a novel approach to boost light emission efficiency, offering remarkable control over light-matter coupling at the sub-wavelength regime. Here, we propose and realise a monolithic scalable integration between intrinsic spin defects in hBN metasurfaces and high quality (Q) factor resonances leveraging quasi-bound states in the continuum (qBICs). Coupling between spin defect ensembles and qBIC resonances delivers a 25-fold increase in photoluminescence intensity, accompanied by spectral narrowing to below 4 nm linewidth facilitated by Q factors exceeding $10^2$. Our findings demonstrate a new class of spin based metasurfaces and pave the way towards vdW-based nanophotonic devices with enhanced efficiency and sensitivity for quantum applications in imaging, sensing, and light emission.

physics.optics↗

arXiv2023

Multiplication of the orbital angular momentum of phonon polaritons via sublinear dispersion

Optical vortices (OVs) promise to greatly enhance optical information capacity via orbital angular momentum (OAM) multiplexing. The need for on-chip integration of OAM technologies has prompted research into subwavelength-confined polaritonic OVs. However, the topological order imprinted by the structure used for the transduction from free-space beams to surface polaritons is inherently fixed after fabrication. Here, we overcome this limitation via dispersion-driven topological charge multiplication. We switch the OV topological charge within a small $\sim 3 \%$ frequency range by leveraging the strong sublinear dispersion of low-loss surface phonon polaritons (SPhP) on silicon carbide membranes. Applying the Huygens principle we quantitatively evaluate the topological order of the experimental OVs detected by near-field imaging. We further explore the deuterogenic effect, which predicts the coexistence of multiple topological charges in higher-order polaritonic OVs. Our work demonstrates a viable method to manipulate the topological charge of polaritonic OVs, paving the way for the exploration of novel OAM-enabled light-matter interactions at mid-infrared frequencies.

physics.optics↗

arXiv2023

Active Huygens' metasurface based on in-situ grown conductive polymer

Active metasurfaces provide unique advantages for on-demand light manipulation at a subwavelength scale for emerging applications of 3D displays, augmented/virtual reality (AR/VR) glasses, holographic projectors and light detection and ranging (LiDAR). These applications put stringent requirements on switching speed, cycling duration, controllability over intermediate states, modulation contrast, optical efficiency and operation voltages. However, previous demonstrations focus only on particular subsets of these key performance requirements for device implementation, while the other performance metrics have remained too low for any practical use. Here, we demonstrate an active Huygens' metasurface based on in-situ grown conductive polymer with holistic switching performance, including switching speed of 60 frames per second (fps), switching duration of more than 2000 switching cycles without noticeable degradation, hysteresis-free controllability over intermediate states, modulation contrast of over 1400%, optical efficiency of 28% and operation voltage range within 1 V. Our active metasurface design meets all foundational requirements for display applications and can be readily incorporated into other metasurface concepts to deliver high-reliability electrical control over its optical response, paving the way for compact and robust electro-optic metadevices.

physics.optics↗

arXiv2023

Metafiber transforming arbitrarily structured light

Structured light has proven useful for numerous photonic applications. However, the current use of structured light in optical fiber science and technology is severely limited by mode mixing or by the lack of optical elements that can be integrated onto fiber end-faces for complex wavefront control, and hence generation of structured light is still handled outside the fiber via bulky optics in free space. We report a metafiber platform capable of creating arbitrarily structured light on the hybrid-order Poincaré sphere. Polymeric metasurfaces, with unleashed height degree of freedom and a greatly expanded 3D meta-atom library, were laser nanoprinted and interfaced with polarization-maintaining single-mode fibers. Multiple metasurfaces were interfaced on the fiber end-faces, transforming the fiber output into different structured-light fields, including cylindrical vector beams, circularly polarized vortex beams, and an arbitrary vector field. Our work provides a new paradigm for advancing optical fiber science and technology towards fiber-integrated light shaping, which may find important applications in fiber communications, fiber lasers and sensors, endoscopic imaging, fiber lithography, and lab-on-fiber technology.

physics.optics↗

arXiv2023

Monolithic Platform for Integrated Quantum Photonics with Hexagonal Boron Nitride

Integrated quantum photonics (IQP) provides a path to practical, scalable quantum computation, communications and information processing. Realization of an IQP platform requires integration of quantum emitters with high quality photonic circuits. However, the range of materials for monolithic platforms is limited by the simultaneous need for a high-quality single photon source, high optical performance and availability of scalable nanofabrication techniques. Here we demonstrate the fabrication of IQP components from the recently emerged quantum material hexagonal boron nitride (hBN), including tapered waveguides, microdisks, and 1D and 2D photonic crystal cavities. Resonators with quality factors greater than 4000 are achieved, and we engineer proof-of-principle complex, free-standing IQP circuitry fabricated from single crystal hBN. Our results show the potential of hBN for scalable integrated quantum technologies.

physics.optics↗

arXiv2023

Spin- and orbital-angular-momentum nonlinear optical selectivity of single-mode nanolasers

Selective control of light is essential for optical science and technology with numerous applications. Nanophotonic waveguides and integrated couplers have been developed to achieve selective coupling and spatial control of an optical beam according to its multiple degrees of freedom. However, previous coupling devices remain passive with an inherently linear response to the power of incident light limiting their maximal optical selectivity. Here, we demonstrate nonlinear optical selectivity through selective excitation of individual single-mode nanolasers based on the spin and orbital angular momentum of light. Our designed nanolaser circuits consist of plasmonic metasurfaces and individual perovskite nanowires, enabling subwavelength focusing of angular-momentum-distinctive plasmonic fields and further selective excitation of single transverse laser modes in nanowires. The optically selected nanolaser with nonlinear increase of light emission greatly enhances the baseline optical selectivity offered by the metasurface from about 0.4 up to near unity. Our demonstrated nonlinear optical selectivity may find important applications in all-optical logic gates and nanowire networks, ultrafast optical switches, nanophotonic detectors, and on-chip optical and quantum information processing.

physics.optics↗