Nature Photonics最新文献

The two-way capacities of quantum channels determine the ultimate entanglement and secret-key distribution rates achievable by two distant parties that are connected by a noisy transmission line, in the absence of quantum repeaters. Since repeaters will likely be expensive to build and maintain, a central open problem of quantum communication is to understand what performances are achievable without them. Here we find a new lower bound on the energy-constrained and unconstrained two-way quantum and secret-key capacities of all phase-insensitive bosonic Gaussian channels, namely thermal attenuator, thermal amplifier and additive Gaussian noise, which are realistic models for the noise affecting optical fibres or free-space links. Ours is the first non-zero lower bound on the two-way quantum capacity in the parameter range where the (reverse) coherent information becomes negative, and it shows explicitly that entanglement distribution is always possible when the channel is not entanglement breaking. This completely solves a crucial open problem of the field, namely establishing the maximum excess noise, which is tolerable in continuous-variable quantum key distribution. In addition, our construction is fully explicit; that is, we devise and optimize a concrete entanglement distribution and distillation protocol that works by combining recurrence and hashing protocols.

Polarized emissive media are crucial for various applications in display, lighting and optical communication. An attractive research direction is to develop intrinsically white organic polarized emissive semiconductors as ideal candidates for miniaturized polarized light-emitting devices; however, it has been a considerable challenge to achieve polarized white-light emission due to the lack of suitable materials and effective preparation methods. Here we overcome this bottleneck by realizing white organic polarized emissive semiconductor single crystals (WOPESSCs). We employ a bimolecular doping method based on using highly polarized, blue-emitting 2,6-diphenylanthracene as the host single crystal, and controlling energy and polarization transfer with green- and red-emitting guests. The fabricated WOPESSCs achieve a photoluminescence quantum yield of 38.3% and a mobility of 4.9 cm² V^–1 s^–1. The emitted light exhibits a degree of polarization as high as 0.96 with Commission Internationale de l’Eclairage coordinates of (0.3258, 0.3396). We also demonstrate the tunable emission properties of WOPESSCs from blue–white to yellow–white light by adjusting polarization angles, and three-primary-colour optical imaging with a wide colour gamut that covers 112% of the National Television System Committee standard. Furthermore, we fabricate highly polarized microscale WOPESSCs light-emitting diodes and light-emitting transistors, achieving high-quality white-light emission and wide-range colour tunability enabled by gate voltage-driven energy transfer processes. We believe these findings pave the way for manufacturing white and multicolour polarized emissive semiconductors and microscale light-emitting devices, promising diverse applications across various fields.

Optical isolation based on a non-reciprocal effect is crucial for proper operation of several high-performance photonic devices such as in telecommunications, light detection and ranging, and even quantum platforms. The magneto-optical Faraday rotation is the most commonly used non-reciprocal effect as it offers unique advantages, including broadband operation, wide input optical power range, low insertion losses and high optical isolation, but it is currently not conducive to miniaturization. Two major impediments hinder the direct integration of Faraday isolators into photonic chips: the need for bulky external magnets and the challenging fabrication of low-loss waveguides that would eliminate the need for free-space coupling optics. Here we have addressed both challenges using a new femtosecond laser writing technique to create waveguides within the bulk of latched bismuth-doped iron garnet slabs without altering its magneto-optic functionality. As a result, we have achieved a Faraday rotator waveguide exhibiting <0.15 dB insertion loss with a figure of merit of 346° dB⁻¹. By interposing this Faraday rotator between two 30-μm-thick polarizers, we further demonstrate a miniaturized optical isolator waveguide with >25 dB isolation ratio and <1.5 dB insertion loss over the entire optical telecom C-band for hybrid integration to photonic circuits without lenses and external magnet.

Nonlinear optics lies at the heart of classical and quantum light generation. The invention of periodic poling revolutionized nonlinear optics and its commercial applications by enabling robust quasi-phase-matching in crystals such as lithium niobate. However, reaching useful frequency conversion efficiencies requires macroscopic dimensions, limiting further technology development and integration. Here we realize a periodically poled van der Waals semiconductor (3R-MoS₂). Owing to its large nonlinearity, we achieve a macroscopic frequency conversion efficiency of 0.03% at the relevant telecom wavelength over a microscopic thickness of 3.4 μm (that is, 3 poling periods), 10–100× thinner than current systems with similar performances. Due to intrinsic cavity effects, the thickness-dependent quasi-phase-matched second harmonic signal surpasses the usual quadratic enhancement by 50%. Further, we report the broadband generation of photon pairs at telecom wavelength via quasi-phase-matched spontaneous parametric down-conversion, showing a maximum coincidence-to-accidental ratio of 638 ± 75. This work opens the new and unexplored field of phase-matched nonlinear optics with microscopic van der Waals crystals, unlocking applications that require simple, ultra-compact technologies such as on-chip entangled photon-pair sources for integrated quantum circuitry and sensing.

Hybridization of excitons with photons to form hybrid quasiparticles—exciton–polaritons (EPs)—has been widely investigated in a range of semiconductor material systems coupled to photonic cavities. Self-hybridization occurs when the semiconductor itself can serve as the photonic cavity medium, resulting in strongly coupled EPs with Rabi splitting energies (ħΩ) of >200 meV at room temperature, which were recently observed in layered two-dimensional excitonic materials. Here we report an extreme version of this phenomenon—an ultrastrong EP coupling—in a nascent, two-dimensional excitonic system, namely, the metal–organic chalcogenolate compound called mithrene. The resulting self-hybridized EPs in mithrene crystals placed on Au substrates show Rabi splitting in the ultrastrong-coupling range (ħΩ > 600 meV) due to the strong oscillator strength of the excitons concurrent with the large refractive indices of mithrene. We further show that bright EP emission occurs at room temperature as well as EP dispersions at low temperatures. Importantly, we find lower EP emission linewidth narrowing to ~1 nm when mithrene crystals are placed in closed Fabry–Pérot cavities. Our results suggest that metal–organic chalcogenolate materials are ideal for polaritonics in the deep green-blue part of the spectrum in which strong excitonic materials with large optical constants are particularly scarce.

We present a comprehensive review of super-resolution optical fluctuation imaging (SOFI), a robust technique that leverages temporal fluctuations in fluorescence intensity to achieve super-resolution imaging without the need for single-molecule localization. The Review starts with a historical overview of super-resolution microscopy techniques, and then focuses on SOFI’s core principle—the analysis of intensity fluctuations using cumulants to improve spatial resolution. The paper discusses technical challenges, such as photobleaching, blinking kinetics and pixel size limitations, as well as proposing solutions like Fourier upsampling and balanced SOFI to mitigate these issues. Additionally, we discuss potential advancements in the field, including the integration of SOFI with other super-resolution modalities like structured illumination microscopy and image scanning microscopy, and the application of SOFI in cryo-fluorescence microscopy and quantum emitter-based imaging. This paper aims to serve as an essential resource for researchers interested in utilizing SOFI for high-resolution imaging in diverse biological applications.

Magnetic field effects on radical pairs in chemical systems are generally well understood and have been successfully investigated with various spectroscopic techniques. However, understanding radical pairs and their quantum nature in biological systems is still in its infancy, which is due to the limitation of high-sensitivity instrumentation. Another reason for this lack of understanding is due to the complexity of biochemical reactions and minute magnetic field-induced changes on radical pair reactions (as low as or lower than a percent). The system design presented here is a new optical system to capture the quantum mechanical nature of biology with a high signal-to-noise ratio. Our magneto-fluorescence fluctuation microspectroscopic approach has the capability of measuring magnetic field effects as low as 0.2% on fluorescence signals near the single-photon level with single-photon avalanche diodes, and is demonstrated by magnetic field effects on 23 molecules. An additional detection system in the form of an EMCCD camera offers spatially resolved magnetic field effects with a novel post hoc digital lock-in amplifier for phase-sensitive camera detection. The aforementioned attributes are demonstrated with radical pair photochemical reactions on model biological systems. The instrument uncovers the importance of photodegradation on protein–flavin interactions via magnetic field effects, which will prove paramount when searching for similar quantum effects in biological locales.

Inverted organic solar cells are attractive for commercialization. However, their power conversion efficiency (PCE) still lags their conventional architecture counterpart. Here we propose a new approach to enhance the performance and stability of structure-inverted non-fullerene organic solar cells. We use an in situ-derived inorganic SiO_xN_y passivation layer, formed by curing a solution-deposited perhydropolysilazane thin film in ambient atmosphere on top of the commonly used ZnO transport layer. Oxygen vacancies and dangling bonds of ZnO create a doped region in the photoactive layer, leading to losses in photocurrent due to enhanced recombination of photogenerated holes within this region. The optimized SiO_xN_y interlayer effectively passivates the ZnO surface defects by forming Zn–O–Si bonds, leading to a vanishing doped region. At the same time, SiO_xN_y induces a preferential accumulation of the non-fullerene acceptor near the electron contact, which also favours charge extraction. The combination of both effects leads to increased photocurrent density and PCE, with certified PCE values of 18.49% and 18.06% for cells with active areas of 5.77 mm² and 100.17 mm², respectively, using PM6:L8-BO as the photoactive layer. Importantly, cells containing inorganic SiO_xN_y exhibit an estimated T₈₀ lifetime of 24,700 h (where T₈₀ is the time it takes for the PCE to drop to 80% of its initial value) under white light illumination, corresponding to an operational lifespan exceeding 16 years. The results underscore the potential of our approach for practical applications of highly efficient and stable inverted organic solar cells.

Surface reflections and non-radiative recombinations create energy losses in perovskite solar cells (PSCs) by hindering the generation and extraction of carriers. These losses can reduce device efficiency in practical applications as the incident angle of sunlight varies throughout the day. Here we introduce a universal strategy to address this issue by coating glass substrates with highly distributed nanoplates of fluorine-doped tin oxide (NP-FTO). An electron-selective homojunction is then formed with a thin layer of SnO₂ deposited by atomic layer deposition covered with SnO₂ quantum dots. Systematic mechanistic studies reveal the exceptional ability of NP-FTO to harvest photons omnidirectionally and its beneficial influence on perovskite crystallization. These combined effects result in substantial improvements in the short-circuit current density, open-circuit voltage and fill factor of n–i–p PSCs under wide-angle incident light illumination. The best-performing PSC achieves a remarkable power conversion efficiency (PCE) of 26.4% (certified 25.9%) under AM1.5G illumination. The devices also show exceptional stability, retaining 95% of their initial PCE after 1,200 hours of light soaking under simulated solar intensity with maximum power point tracking. Moreover, the beneficial effects of NP-FTO are also applicable to 1.77 eV wide-bandgap PSCs with a p–i–n structure, enabling the fabrication of all-perovskite tandem solar cells with a best PCE of 28.2%.

High-power amplifiers are critical components in optical systems spanning from long-range optical sensing and optical communication systems to micromachining and medical surgery. Today, integrated photonics with its promise of large reductions in size, weight and cost cannot be used in these applications, owing to the lack of on-chip high-power amplifiers. Integrated devices severely lack in output power owing to their small size, which limits their energy storage capacity. For the past two decades, large mode area (LMA) technology has played a disruptive role in fibre amplifiers, enabling a dramatic increase of output power and energy by orders of magnitude. Owing to the ability of LMA fibres to support significantly larger optical modes, the energy storage and power handling capabilities of LMA fibres have significantly increased. Therefore, an LMA device on an integrated platform can play a similar role in power and energy scaling of integrated devices. In this work, we demonstrate LMA waveguide-based watt-class high-power amplifiers in silicon photonics with an on-chip output power exceeding ~1 W within a footprint of only ~4.4 mm². The power achieved is comparable and even surpasses that of many fibre-based amplifiers. We believe that this work has the potential to radically change the integrated photonics application landscape, allowing power levels previously unimaginable from an integrated device to replace much of today’s benchtop systems. Moreover, mass producibility, reduced size, weight and cost will enable yet unforeseen applications of laser technology.