High-performance Photon Research Articles

Bottom-Up Formation of III-Nitride Nanowires: Past, Present, and Future for Photonic Devices.

The realization of semiconductor heterostructures marks a significant advancement beyond silicon technology, driving progress in high-performance optoelectronics and photonics, including high-brightness light emitters, optical communication,and quantum technologies. In less than a decade since 1997, nanowires research has expanded into new application-driven areas,highlighting a significant shift toward more challenging and exploratory research avenues. It is therefore essential to reflecton the past motivations for nanowires development, and explorethe new opportunities it can enable. The advancement of heterogeneous integration using dissimilar substrates, materials, and nanowires-semiconductor/electrolyte operating platforms is ushering in new research frontiers, including the development of perovskite-embedded solar cells, photoelectrochemical (PEC) analog and digital photonic systems, such as PEC-basedphotodetectors and logic circuits, as well as quantum elements, such assingle-photon emitters and detectors. This review offersrejuvenating perspectives on the progress of these group-III nitride nanowires,aiming to highlight the continuity of research toward high impact, use-inspired researchdirections in photonics and optoelectronics.

Optical switching with high-Q Fano resonance of all-dielectric metasurface governed by bound states in the continuum

The discovery of bound states in the continuum (BIC) of optical nanostructures has garnered significant research interest and found widespread application in the field of optics, leading to an attractive approach to achieve high-Q (Quality factor) Fano resonance. Herein, an all-dielectric metasurface consisting of four gallium phosphide (Gap) cylinders on the MgF2 substrate is designed and analyzed by the finite element method (FEM). By breaking the symmetry of the plane, specifically by moving the two cylinders to one side, it is possible to achieve a transition from the symmetry-protected BIC to quasi-BIC. This transition enables the excitation of sharp dual-band Fano resonance at wavelengths of 1,045.4 nm and 1,139.6 nm, with the maximum Q factors reaching 1.47 × 104 and 1.28 × 104, respectively. The multipole decomposition and near-field distributions show that these two QBICs are dominated by the electric quadrupole (EQ) and magnetic quadrupole (MQ). Furthermore, bidirectional optical switching can be accomplished by changing the polarization direction of the incident light. As a result, the maximum sensitivity and figure of merit (FOM) are 488.9 nm/RIU and 2.51 × 105 RIU-1, respectively. The results enrich our knowledge about BIC and reveal a platform for the development of high-performance photonics devices such as optical switches and sensors.

High-performance photon number resolving detectors for 850–950 nm wavelength range

Since their first demonstration in 2001 [Gol’tsman et al., Appl. Phys. Lett. 79, 705–707 (2001)], superconducting-nanowire single-photon detectors (SNSPDs) have witnessed two decades of great developments. SNSPDs are the detector of choice in most modern quantum optics experiments and are slowly finding their way into other photon-starved fields of optics. Until now, however, in nearly all experiments, SNSPDs were used as “binary” detectors, meaning that they could only distinguish between 0 and >=1 photons, and photon number information was lost. Recent research has demonstrated proof-of-principle photon-number resolution (PNR) SNSPDs counting 2–5 photons. The photon-number-resolving capability is highly demanded in various quantum-optics experiments, including Hong–Ou–Mandel interference, photonic quantum computing, quantum communication, and non-Gaussian quantum state preparation. In particular, PNR detectors at the wavelength range of 850–950 nm are of great interest due to the availability of high-quality semiconductor quantum dots (QDs) [Heindel et al., Adv. Opt. Photonics 15, 613–738 (2023)] and high-performance cesium-based quantum memories [Ma et al., J. Opt. 19, 043001 (2017)]. In this paper, we demonstrate NbTiN-based SNSPDs with >94% system detection efficiency, sub-11 ps timing jitter for one photon, and sub-7 ps for 2 photons. More importantly, our detectors resolve up to 7 photons using conventional cryogenic electric readout circuitry. Through theoretical analysis, we show that the PNR performance of demonstrated detectors can be further improved by enhancing the signal-to-noise ratio and bandwidth of our readout circuitry. Our results are promising for the future of optical quantum computing and quantum communication.

Optical switching with high-Q Fano resonance of all-dielectric metasurface governed by bound states in the continuum

The discovery of bound states in the continuum (BIC) of optical nanostructures has garnered significant research interest and found widespread application in the field of optics, leading to an attractive approach to achieve high-Q (Quality factor) Fano resonance. Herein, an all-dielectric metasurface consisting of four gallium phosphide (Gap) cylinders on the MgF2 substrate is designed and analyzed by the finite element method (FEM). By breaking the symmetry of the plane, specifically by moving the two cylinders to one side, it is possible to achieve a transition from the symmetry-protected BIC to quasi-BIC. This transition enables the excitation of sharp dual-band Fano resonance at wavelengths of 1,045.4 nm and 1,139.6 nm, with the maximum Q factors reaching 1.47 × 104 and 1.28 × 104, respectively. The multipole decomposition and near-field distributions show that these two QBICs are dominated by the electric quadrupole (EQ) and magnetic quadrupole (MQ). Furthermore, bidirectional optical switching can be accomplished by changing the polarization direction of the incident light. As a result, the maximum sensitivity and figure of merit (FOM) are 488.9 nm/RIU and 2.51 × 105 RIU−1, respectively. The results enrich our knowledge about BIC and reveal a platform for the development of high-performance photonics devices such as optical switches and sensors.

Effect of polymer concentration on molecular alignment behavior during scanning wave photopolymerization

Molecularly aligned liquid-crystalline (LC) polymer films hold great promise for next-generation high-performance photonics, electronics, robotics, and medical devices. Photoalignment methods capable of achieving precise molecular alignment in a noncontact manner have been actively studied. Recently, we proposed the concept of using spatiotemporal photopolymerization to induce molecular diffusion and the resulting alignment, termed scanning wave photopolymerization (SWaP). The spatial gradient of the polymer concentration is the dominant factor in inducing the molecular diffusion and alignment of LCs. However, the effect of polymer concentration on molecular alignment behavior remains unclear. In this study, we performed SWaP at different exposure energies to modulate the polymer concentration during polymerization. We found that a certain polymer concentration was required to initiate the alignment. Furthermore, the phase diagram of the polymer/monomer mixtures and real-time observations during SWaP revealed that phase emergence and unidirectional molecular alignment occurred simultaneously when the polymer concentration exceeded 50%. Since SWaP achieves molecular alignment coincident with photopolymerization, it has the potential to revolutionize material fabrication by consolidating the multiple-step processes required to create functional materials in a single step.

Low Temperature Synthesis of 2D p-Type α-In2Te3 with Fast and Broadband Photodetection.

2D compounds (A = Al, Ga, In, and B = S, Se, and Te) with intrinsic structural defects offer significant opportunities for high-performance and functional devices. However, obtaining 2D atomic-thin nanoplates with non-layered structure on SiO2/Si substrate at low temperatures is rare, which hinders the study of their properties and applications at atomic-thin thickness limits. In this study, the synthesis of ultrathin, non-layered α-In2Te3nanoplates is demonstrated using a BiOCl-assisted chemical vapor deposition method at a temperature below 350°C on SiO2/Si substrate. Comprehensive characterization results confirm the high-quality single crystal is the low-temperature cubic phase α-In2Te3 , possessing a noncentrosymmetric defected ZnS structure with good second harmonic generation. Moreover, α-In2Te3 is revealed to be a p-type semiconductor with a direct and narrow bandgap value of 0.76eV. The field effect transistor exhibits a high mobility of 18 cm2 V-1s-1,and the photodetector demonstrates stable photoswitching behavior within a broadband photoresponse from 405 to 1064nm, with a satisfactory response time of τrise = 1ms. Notably, the α-In2Te3 nanoplates exhibit good stability against ambient environments. Together, these findings establish α-In2Te3 nanoplates as promising candidates for next-generation high-performance photonics and electronics.

Quasi-2D Dion-Jacobson phase perovskites as a promising material platform for stable and high-performance lasers.

Metal halide perovskites have shown outstanding optoelectronic and nonlinear optical properties; yet, to realize wafer-scale high-performance perovskite-integrated photonics, the materials also need to have excellent ambient stability and compatibility with nanofabrication processes. In this work, we introduce Dion-Jacobson (D-J) phase perovskites for photonic device applications. By combining self-assembled monolayer-assisted film growth with thermal pressing, we obtain a series of compact and extremely smooth D-J phase perovskite thin films that exhibit excellent stability during electron-beam lithography, solvent development, and rinse. Combining spectroscopic and morphological characterizations, we further demonstrate how organic spacers can be used to fine-tune the photophysical properties and processability of the perovskite films. The distributed-feedback lasers based on the D-J phase perovskites exhibit a low lasing threshold (5.5 μJ cm-2 pumped with nanosecond laser), record high Q factor (up to 30,000), and excellent stability, with an unencapsulated device demonstrating a T90 beyond 60 hours in ambient conditions (50% relative humidity).

Heterogeneous optomechanical crystal cavity coupled by a wavelength-scale mechanical waveguide

Integrated optomechanical crystal (OMC) cavities provide a vital device prototype for highly efficient microwave to optical conversion in quantum information processing. In this work, we propose a novel heterogeneous OMC cavity consisting of a thin-film lithium niobate (TFLN) slab and chalcogenide (ChG) photonic crystal nanobeam coupled by a wavelength-scale mechanical waveguide. The optomechanical coupling rate of the heterogeneous OMC cavity is optimized up to 340 kHz at 1.1197 GHz. Combined with phononic band and power decomposition, 17.38% energy from the loaded RF power is converted into dominant fundamental horizontal shear mode (SH0) in the narrow LN mechanical waveguide. Based on this fraction, as a result, 3.51% power relative to the loaded RF energy is scattered into the fundamental longitudinal mode (L0) facing the TFLN-ChG heterogeneous waveguide. The acoustic breathing mode of the heterogeneous OMC is successfully excited under the driving of the propagating L0 mode in the heterogeneous waveguide, demonstrating the great potentials of the heterogeneous piezo-optomechanical transducer in high-performance photon–phonon interaction fields.

High-Performance Dual-Channel Photonic Crystal Terahertz Wave Modulator Based on the Defect Mode Disappearance of a Combined Microcavity

With the working frequency of wireless communication systems moving to a higher terahertz (THz) band, the design of high-performance THz wave modulators has become a pivotal issue to be tackled urgently in THz communication. In this paper, we design a high-performance dual-channel photonic crystal modulator to enable ON–OFF regulation of the THz wave based on the defect mode disappearance of combined microcavities. The modulator introduces Y-type line defects into silicon rod photonic crystals as a dual-channel waveguide and the point defects and ring resonator form a combined microcavity. Due to the refractive index of the ring resonator filler, gallium arsenide, it is tunable with pump light excitation, and the defect mode frequency of the combined microcavity can be dynamically changed. Under pump excitation with a wavelength of 810 nm and an intensity of 0.4 μJ/cm2, 1.34 THz and 1.83 THz dual-channel waves can be OFF due to the defect mode disappearance of the combined microcavity. This is simulated by the time-domain steady-state response and steady-state THz wave field intensity distribution of the modulator by the finite-difference time-domain method. The results indicate that the dual-channel modulator has large modulation depths of 100% and 99.7%, high modulation rates of 4.05 GHz and 4.17 GHz, and low insertion losses of 0.31 dB and 0.18 dB, which lays foundation for the development of high-speed and low-loss THz communication technology.

Photonic-chip-based dense entanglement distribution

The dense quantum entanglement distribution is the basis for practical quantum communication, quantum networks and distributed quantum computation. To make entanglement distribution processes stable enough for practical and large-scale applications, it is necessary to perform them with the integrated pattern. Here, we first integrate a dense wavelength-division demultiplexing system and unbalanced Mach-Zehnder interferometers on one large-scale photonic chip and demonstrate the multi-channel wavelength multiplexing entanglement distribution among distributed photonic chips. Specifically, we use one chip as a sender to produce high-performance and wideband quantum photon pairs, which are then sent to two receiver chips through 1-km standard optical fibers. The receiver chip includes a dense wavelength-division demultiplexing system and unbalanced Mach-Zehnder interferometers and realizes multi-wavelength-channel energy-time entanglement generation and analysis. High quantum interference visibilities prove the effectiveness of the multi-chip system. Our work paves the way for practical entanglement-based quantum key distribution and quantum networks.

Plasmonic Terahertz Devices and Sensors Based on Carbon Electronics.

Tunable terahertz (THz) photonic devices are imperative in a wide range of applications ranging from THz signal modulation to molecular sensing. One of the currently prevailing methods is based on arrays of metallic or dielectric resonators integrated with functional materials in response to an external stimulus, in which for the purpose of sensing the external stimuli may introduce inadvertent undesirable effects into the target samples to be measured. Here we developed an alternative approach by postprocessing nanothickness macro-assembled graphene (nMAG) films with widely tunable THz conductivity, enabling versatile solid-state THz devices and sensors, showing multifunctional nMAG-based applications. The THz conductivities of free-standing nMAGs showed a broad range from 1.2 × 103 S/m in reduced graphene oxide before annealing to 4.0 × 106 S/m in a nMAG film annealed at 2800 °C. We fabricated nMAG/dielectric/metal and nMAG/dielectric/nMAG THz Salisbury absorbers with broad reflectance ranging from 0% to 80%. The highly conductive nMAG films enabled THz metasurfaces for sensing applications. Taking advantage of the resonant field enhancement arising from the plasmonic metasurface structures and the strong interactions between analyte molecules and nMAG films, we successfully detected diphenylamine with a limit of detection of 4.2 pg. Those wafer-scale nMAG films present promising potential in high-performance THz electronics, photonics, and sensors.

Strong enhancement of electromagnetic shower development induced by high-energy photons in a thick oriented tungsten crystal

We have observed a significant enhancement in the energy deposition by 25–100~textrm{GeV} photons in a 1~textrm{cm} thick tungsten crystal oriented along its langle 111 rangle lattice axes. At 100~textrm{GeV}, this enhancement, with respect to the value observed without axial alignment, is more than twofold. This effect, together with the measured huge increase in secondary particle generation is ascribed to the acceleration of the electromagnetic shower development by the strong axial electric field. The experimental results have been critically compared with a newly developed Monte Carlo adapted for use with crystals of multi-X_0 thickness. The results presented in this paper may prove to be of significant interest for the development of high-performance photon absorbers and highly compact electromagnetic calorimeters and beam dumps for use at the energy and intensity frontiers.

Ultrathin quantum light source with van der Waals NbOCl2 crystal.

Interlayer electronic coupling in two-dimensional materials enables tunable and emergent properties by stacking engineering. However, it also results in significant evolution of electronic structures and attenuation of excitonic effects in two-dimensional semiconductors as exemplified by quickly degrading excitonic photoluminescence and optical nonlinearities in transition metal dichalcogenides when monolayers are stacked into van der Waals structures. Here we report a van der Waals crystal, niobium oxide dichloride (NbOCl2), featuring vanishing interlayer electronic coupling and monolayer-like excitonic behaviour in the bulk form, along with a scalable second-harmonic generation intensity of up to three orders higher than that in monolayer WS2. Notably, the strong second-order nonlinearity enables correlated parametric photon pair generation, through a spontaneous parametric down-conversion (SPDC) process, in flakes as thin as about 46 nm. To our knowledge, this is the first SPDC source unambiguously demonstrated in two-dimensional layered materials, and the thinnest SPDC source ever reported. Our work opens an avenue towards developing van der Waals material-based ultracompact on-chip SPDC sources as well as high-performance photon modulators in both classical and quantum optical technologies1-4.

Progress in the synthesis of 2D black phosphorus beyond exfoliation

A considerable number of recent research have focused on two-dimensional (2D) black phosphorus (BP) since it was successfully prepared through mechanical exfoliation in 2014. After scaling down, BP with atomistic thickness shows fascinating semiconducting features with layer-dependent direct bandgap and high carrier mobility. The synthesis of high-quality few-layer BP thin films is critical to investigate their distinctive crystal structure, fundamental characteristics, as well as the potential applications in electronics, biomedicine, energy storage, photonics, and optoelectronics. Therefore, this review provides an overview of mono- and few-layer BP topic in the synthesis methods beyond exfoliation, including thinning treatments accompanied to exfoliation, conversion from red phosphorus to BP, and direct growth techniques. We summarize various attempts to control the BP sample's thickness and lateral dimensions during the synthesis. Furthermore, we discuss the current challenges and perspectives of large-scale growth of ultrathin BP which has been a bottleneck hindering wafer-scale device's development in this field. We hope to provide an insight into exploring some potential approaches practicable to synthesize high quality BP thin films utilized for developing high-performance nano-electronics and photonics, which may accelerate the progress of 2D BP toward real applications.

High Performance Photonic Nanostructured Sensors for Smart Industries: Design and Analysis

High Performance Photonic Nanostructured Sensors for Smart Industries: Design and Analysis

Side-Chain Engineering of Polystyrene Dielectrics Toward High-Performance Photon Memories and Artificial Synapses

The emerging applications of organic field-effect transistors (OFETs), such as photon memories and artificial synapses, require polymer dielectrics with superior charge trapping properties. Despite the introduction of high-k and fluorinated polymers in the performance optimization of OFETs, there is still a lack of widely recognized acknowledgment between molecular structures and charge trapping characteristics, as well as no general principles in designing polymeric dielectrics for electronic memory devices. Here, we propose a series of fluorinated polystyrene isomers through side-chain engineering, namely, ortho-(o-), meta-(m-), and para-fluorinated polystyrene (p-FPS). The gradually enlarged intramolecular charge separation of o-, m-, and p-FPS enhances molecular electrostatic potential, which promotes polarization and charge trapping performances, resulting in an enlarged dielectric constant, as well as more deep traps toward stable electret. Subsequently, largely improved photon memory and artificial synapse performances of p-FPS-based OFETs further suggest the dominating role of dielectric side-chain structures on memory and synapse performances, leading to a recommendation of low-k (εr < 5) dielectric polymers with enhanced electrostatic potential for OFET-based memory devices and bionic nervous systems.

High-performance 2D photonics MOEMS pressure sensors

High-performance 2D photonics MOEMS pressure sensors

Development of an autotuning magnet girder with high stability and accuracy

With the development of high-performance photon sources which have extremely low emittance, autotuning magnet girders have drawn more and more attention, especially for diffraction-limited storage rings and free-electron lasers. The biggest challenge is to simultaneously obtain high stability and high flexibility. In this paper, an autotuning magnet-girder prototype has been designed and developed. Topological optimization, multipoint supports, and locking systems have been applied for magnet-girder design to improve the stability. The modal analysis accords with the vibration test well. The natural frequency of the magnet-girder assembly is deduced as high as 45.6 Hz, which demonstrates good stability. Ball-cam movers have been chosen as adjustment mechanisms, and a closed-loop control scheme has been used to pursue high accuracy. The kinematic resolution is better than $1\text{ }\text{ }\ensuremath{\mu}\mathrm{m}$, and the accuracy is better than $1\text{ }\text{ }\ensuremath{\mu}\mathrm{m}$ within the adjusting range of $\ifmmode\pm\else\textpm\fi{}5\text{ }\text{ }\mathrm{mm}$. Besides, it can eliminate most of the calibration, which can save much manpower and time. The tests demonstrate that the magnet girder can be used for beam-based girder alignment with high stability and high accuracy.

High-Performance Silicon Photonics Using Heterogeneous Integration

The performance of silicon photonic components and integrated circuits has improved dramatically in recent years. As a key enabler, heterogeneous integration not only provides the optical gain which is absent from native Si substrates and enables complete photonic functionalities on chip, but also lays the foundation of versatile integrated photonic device performance engineering. This paper reviews recent progress of high-performance silicon photonics using heterogeneous integration, with emphasis on ultra-low-loss waveguides, single-wavelength lasers, comb lasers, and photonic integrated circuits including optical phased arrays for LiDAR and optical transceivers for datacenter interconnects.

Precise morphology control of in-plane silicon nanowires via a simple plasma pre-treatment

Silicon nanowires (SiNWs) are advantageous building blocks to explore a wide range of high performance nanoelectronics and photonics devices. In-plane solid-liquid-solid (IPSLS) SiNWs, grown by metal catalyst droplets that absorb hydrogenated amorphous silicon (a-Si:H) thin film to produce crystalline SiNWs, are particularly suitable for planar device fabrication and integration. Here, we explore a new growth control dimension to tailor the geometry of the in-plane SiNWs from island-chain to zigzag and to straight morphologies by using a simple plasma modification of the a-Si:H thin film precursor. This unique capability is due to fact that the Gibbs energy and bonding status of the a-Si:H layer can be largely modified by the plasma treatments at various substrate temperatures, which in turn have a huge impact on the growth balance condition of the SiNWs and consequently on their morphologies. These results highlight a facile and yet highly effective strategy to tailor the morphologyof in-plane SiNWs that will find important applications in fabricating nanoelectronic, sensor and logic devices.