Renewed interest in near-field thermal radiation stems from its potential in energy harvesting, nanoscale thermal management, and thermophotovoltaics, driving efforts to understand and engineer its fundamental mechanisms. Plasmonic materials are well recognized for their ability to enhance fields proximal to their surfaces; however, detailed quantitative assessment of the field intensity and energy density of thermal radiation in the near field (relative to the far field) and potential practical impact is lacking. This work presents a detailed study of a prototypical metamaterial design supporting plasmon resonance in the mid-infrared spectrum. Significant intensification of thermal radiation in near field is investigated using a numerical finite-difference time-domain method that incorporates randomly fluctuating dipoles in accordance with the fluctuation-dissipation theorem that enables excitation of high-order spatial harmonics. Electromagnetic response of the metamaterial thermal emitter to both thermal and optical excitations is evaluated and compared. Findings indicate that the near field intensity at a mere 500 nm from the metamaterial surface exhibits an enhancement of up to 38-fold in near-field electromagnetic energy density relative to the corresponding far-field value at 4.8 μm lying near the edge of Brillouin zone under thermal excitation. In contrast, 6-fold enhancement is observed at 4.35 μm lying near the center of the Brillouin zone under optical excitation. Further, thermal excitation yields a 3.5-fold increase in peak intensity compared to conventional blackbody radiation at 2 μm away from the outermost layer of the metamaterial. Moreover, photothermal simulations further reveal rapid temperature rises exceeding 600 K within nanoseconds under low-power pulsed excitation. These results demonstrate that thermal excitation enables access to dark electromagnetic modes that dominate near-field radiation and highlight the importance of excitation mechanism in designing metamaterial-based thermal photonic devices.
Parkinson’s disease (PD) has afflicted numerous patients and troubled countless families worldwide, but an effective therapeutic approach has not been discovered so far. Yet, emerging evidence suggested that photobiomodulation (PBM) can fundamentally delay and inhibit neuronal degeneration, and thus promisingly serve as a non-invasive alternative to conventional drug and surgical treatments. Nevertheless, the light wavelength and spectrum are crucial to PBM. To optimize the spectral formula of photomedicine and reveal photobiological effects, an acute PD model by injecting paraquat into mice abdomen was established in this study. Then, these mice were treated with the narrowband light-emitting diode (LED)-chip light peaked at 670 nm, the broadband phosphor-converted LED light peaked at 840 nm in 600−1000 nm region, and their combination. The results indicate that the PBM is safe, and the combined (narrow 670 + broad 840 nm) light exerted the most potent therapeutic effects. It significantly attenuated oxidative stress levels, enhanced axonal regeneration, protected dopaminergic neurons in the substantia nigra pars compacta (SNpc), preserved striatal neuronal integrity, and improved neuronal morphology and marker expression. Thereby, broadband wavelength through multitarget synergistic therapy helps to improving pathological features and facilitating neural function repair in acute PD mice. However, behavioral validation remains necessary in future studies and further richens the spectrum engineering to PBM.
Glass light guide plates (LGPs) are widely employed in ultrathin display applications due to their excellent optical transmittance, chemical stability, and mechanical strength. The fabrication of microholes with precisely controlled morphology on glass surfaces using ultrafast lasers is crucial for further enhancing the optical performance of LGPs. However, the interaction mechanisms between ultrafast lasers and glass have not yet been precisely described, and the insufficient consideration of inter-pulse interactions under high repetition frequency conditions leads to limited predictive accuracy for microhole morphology. Here, a rotary laser processing system is employed for the high-efficiency fabrication of glass LGPs. To address the moving multi-pulse laser irradiation scenario, an improved two-temperature model (TTM) incorporating the laser incubation effect is proposed, enabling the calculation of both the material temperature field and the evolution of microhole morphology during the moving multi-pulse laser processing. The model is experimentally validated using a rotational laser processing system, and the simulated results agree well with both single- and multi-pulse microhole ablation under various laser parameters. For LGP applications, a strategy is further proposed to obtain conical microholes suitable for LGP operation by controlling the pulse number at different processing speeds, thereby enhancing optical performance. This multi-pulse laser ablation model for glass provides important theoretical guidance for microhole fabrication in LGPs and demonstrates significant engineering application value.
All-lead sulfide (PbS) quantum dot (QD) tandem solar cells (TSCs) offer a promising pathway to surpass single-junction efficiency limits. However, their performance is hindered by the vulnerability of the wide-bandgap (WBG) top cell, which suffers chemical and physical damage during the deposition of 1,2-ethanedithiol (EDT)-capped hole-transport layers (HTLs) and interconnecting layers. This results in morphological voids and interfacial trap states. Here, we introduce a chlorinated benzodithiophene-based conjugated copolymer (D18-Cl) as a multifunctional interfacial passivator at the WBG/HTL interface. D18-Cl could bind to unsaturated Pb sites via chlorine and passivate sulfur vacancies through thiophene ring coordination. This strategy eliminates pinholes and shields the WBG absorber from subsequent processing damage. Furthermore, D18-Cl modification aligns the energy levels by elevating the highest occupied molecular orbital (HOMO) level of the absorber, creating a graded pathway that reduces the hole-extraction barrier and suppresses non-radiative recombination. Consequently, the D18-Cl-modified semitransparent WBG cell achieves a power conversion efficiency (PCE) of 10.36%. When integrated into a monolithic TSC, the device yields a record PCE of 13.148% with an unprecedented fill factor of 73.14%. The encapsulated TSC retains over 90% of its initial PCE after 500 h of MPP tracking, demonstrating exceptional stability.
This paper proposes a robust design for a free-space optical (FSO) system assisted by an unmanned aerial vehicle (UAV) equipped with an intelligent reflecting surface (IRS), operating under probabilistic malicious jamming. The UAV-carried IRS establishes an auxiliary link when the direct path is blocked. The system experiences composite fading (saturated turbulence, pointing errors, and angle-of-arrival fluctuations), and the jammer's intermittent activity is modeled by a Bernoulli process. We derive a closed-form expression for the average outage probability (OP) under this unified channel-and-jamming model. To address the critical performance-cost trade-off, a bi-objective optimization problem is formulated to jointly minimize the OP and the hardware deployment cost. An alternating optimization (AO) algorithm is proposed to solve the resulting mixed-integer nonlinear programming problem by decoupling it into discrete (number of IRS elements) and continuous (power, angles, apertures) subproblems, which are efficiently handled via integer search and particle swarm optimization, respectively. Simulation results demonstrate that the proposed AO algorithm converges within 15 iterations, substantially faster than genetic algorithm and random search, and achieves a near-optimal trade-off, reducing outage probability by an order of magnitude compared to non-optimized benchmarks while keeping hardware cost within budget.
In this paper, the authors demonstrate high-fidelity chaotic synchronization in a programmable synthetic temporal lattice and achieve accurate signal transmission for arbitrary-intensity messages using an alternate encoding strategy. By constructing a synthetic temporal lattice with truncated boundaries via coupled fiber loops and incorporating optoelectronic feedback to introduce controllable artificial nonlinearity, they generate discrete chaotic pulse sequences with tunable entropy. A chaotic synchronization scheme is then implemented within the same synthetic temporal lattice for signal transmission. In this scheme, each message bit is alternately loaded onto the chaotic carrier at single-pulse intervals, allowing the unmodulated carrier pulses at the transmitter to precisely drive synchronized chaotic pulses at the receiver. Experimental results show that nearly perfect synchronization and near-zero decoding error are achieved regardless of the injected message intensity. The study establishes a reconfigurable synthetic-dimensional platform for controllable optical chaos and its high-fidelity application in secure signal transmission.
The miniaturization of imaging systems is essential for modern optoelectronics, while traditional bulk optics fundamentally limit integration density. Metasurfaces offer a transformative planar alternative by providing nanoscale control over incident light. However, realizing their full potential requires transitioning from discrete optical components to fully integrated sensing architectures. This review surveys the progressive integration of metasurface with photodetectors and image sensors. We examine the developmental trajectory across three distinct levels: free-space optical path placement, hybrid adhesive mounting and direct monolithic fabrication. Particular emphasis is placed on monolithic architectures and their role in enabling multi-dimensional information extraction. Finally, we discuss emerging challenges in material compatibility and scalable manufacturing to provide clear directions for future ultracompact optoelectronic device development.
In this paper, we report a mode-interference-based approach for the efficient and reliable diameter measurement of micro/nanofibers (MNFs), enabling the in situ monitoring of MNFs fabricated from both single-mode fibers (SMFs) and multimode fibers (MMFs). The proposed method integrates automated signal processing with parameter-corrected flamebrush models, establishing a real-time closed-loop feedback mechanism during the fabrication process. Within the 524-1778 nm range, measurement accuracies better than 8 nm (< 1.25%) for SMF and 5 nm (< 0.78%) for MMF are demonstrated. Furthermore, to address the challenge of reconstructing complex taper profiles, we introduce a one-dimensional convolutional neural network (1D-CNN). Trained on a physics-enhanced data set, this network enables the end-toend precision measurement of taper morphology. Within the diameter range of 1.9-10 & micro;m, the maximum relative error is maintained below 0.35%, with a maximum absolute error of less than 9 nm. This method demonstrates broad applicability, offering a reliable solution for the fabrication of high-performance MNF-based photonic devices.
Structured light, with its multidimensional control over amplitude, phase, space and frequency, is a key enabler for advanced technologies such as high-capacity communications, quantum information, and super-resolution imaging. Here, we propose a unified inverse-design methodology for arbitrary on-chip vectorial structured-light. Inspired by quantum-state representations, we describe complex vector fields as finite-dimensional vectors in a Hilbert space and introduce a transmission-matrix formalism that links input waveguide modes to target topological edge states. By combining this mapping with adjoint-based topology optimization, we obtain the permittivity distribution within a compact design window that realizes the desired vector transformation while preserving topological transport. We experimentally demonstrate two representative domain-wall configurations on a valley photonic crystal (VPC) platform, termed Type-I and Type-II topological couplers, which efficiently couple the fundamental mode into valley pseudospin edge states. Simulations of the ideally designed device show insertion losses of 0.04 dB and 0.09 dB at 1550 nm with 3-dB bandwidths of 132 nm and 65 nm, respectively. Experimentally, the fabricated device, which was designed accounting for fabrication tolerances, maintains a broadband low-loss performance, with measured losses of < 0.6 dB at 1550 nm with 3-dB bandwidth over > 60 nm and < 0.8 dB at 1550 nm with 3-dB bandwidth over 87 nm. Mirror-symmetric designs further validate selective excitation of orthogonal pseudospin states. Our results establish this inverse-design methodology as a powerful tool for strictly controlling on-chip vectorial light, paving the way toward compact, broadband, and multifunctional photonic integrated circuits for optical computing, communications, and beyond.
Over the past decade, perovskite light-emitting diodes (PeLEDs) have garnered extensive attention due to their remarkable progress in external quantum efficiency (EQE). The EQE for red and green emission has surpassed 30%, while blue PeLEDs have also exceeded 20%, rendering them a highly competitive technology for next-generation displays. This article provides a comprehensive review of milestones for PeLEDs, recording the key performances including EQE, peak luminance, and operational lifetime. Furthermore, we discuss the prevailing challenges that PeLEDs must overcome in their near-future development. This work aims to outline encouraging achievements of PeLEDs and draw a roadmap to accelerate their commercialization.
Two-dimensional (2D) all-inorganic halide perovskites exhibit promise for optoelectronic applications, yet selective exfoliation along specific crystallographic planes remains a critical challenge for performance optimization. Using first-principles calculations combined with device simulations, we systematically investigated the structural stability, exfoliation feasibility, and optoelectronic properties of 24 all-inorganic 2D perovskites derived from the (100) and (111) planes of cubic perovskites, specifically the A2BX4 and A3B ' 2X9 series (A = Cs, Rb; B = Pb, Sn; B ' = Bi, Sb; X = Cl, Br, I). Our results demonstrate that (111)-derived A3B ' 2X9 perovskites exhibit significantly lower exfoliation energies (23.1-62.1 meV/& Aring;2) than (100)-derived A2BX4 counterparts (59.7-174.0 meV/& Aring;2), attributed to weaker van der Waals interlayer coupling in the former. Rb3Bi2I9 possesses an ultralow exfoliation energy of 23.1 meV/& Aring;2, rivaling that of graphene and demonstrating exceptional potential for mechanical exfoliation of high-quality monolayers. A2BX4 monolayers exhibit direct band gaps, which are favorable for optoelectronic applications; whereas A3B ' 2X9 monolayers display indirect band gaps. Among all investigated materials, monolayer Rb2SnBr4 emerges as an outstanding candidate, featuring an ideal direct band gap of 1.34 eV (HSE06) that perfectly matches the Shockley-Queisser limit for single-junction solar cells. SCAPS-1D device simulations further predict that optimized Rb2SnBr4-based solar cells can achieve a remarkable theoretical power conversion efficiency of 27.10% under defect densities below 1014 cm-3. This work establishes that (111) plane cleavage is optimal for synthesizing exfoliable 2D perovskites, while (100) plane orientation enables superior direct band gap characteristics for photovoltaic applications, providing critical design principles for crystallographic plane engineering in halide perovskite devices.
The optical diffractive neural network (ODNN), based on the free-space propagation of light waves, exhibits significant ad-vantages, including ultra-high speed, low power consumption, and parallel computation. However, this technology faces challenges in practical applications, particularly concerning fabrication and alignment accuracy, with stringent requirements on manufacturing processes. In this paper, a class of hybrid optical diffractive neural networks (H-ODNNs) is designed by constructing continuous passive phase modulation layers using diffraction neurons of varying sizes. Three representative tasks (digit recognition, image processing, and wavelength multiplexing) substantiate its superior performance in enhancing robustness. Compared with network with vaccination (a common method for enhancing robustness), the H-ODNN does not need vaccination training, the average training time is reduced by approximately 50%, and even achieves superior performance. Additionally, the larger size of some diffraction neurons, the H-ODNN reduces the complexity of fabrication and improves manufacturing yield. This work provides a new concept for the design of ODNN.
In this paper, we report multi-component gas analysis from a narrow overlapping near-infrared spectral window using second-harmonic photothermal interferometry (PTI) combined with partial least-squares regression (PLSR). The analytes in a 5 cm hollow core Fabry-P & eacute;rot probe are pumped by a 40 mW DFB laser tuned from 1680 nm to 1681.2 nm and probed at 1570 nm. A total of 460 spectra for the gases CH4, C2H6, and C2H4 at different concentrations were automatically recorded, with each spectrum containing 520 points. Using 80%/20% train/validation splits and 5-fold cross-validation, the PLSR model exhibits an overall relative error of 0.319%. The model predictions can maintain a good relative error of about 0.5% with only 180 training samples, or 150 attention-focused points, or 33-point down-sampled spectra. This narrow-band single-laser fiber-integrated PTI with PLSR would enable accurate gas component prediction for industrial and medical applications.
In this paper, we demonstrate a compact broadband on-chip radio-frequency (RF) termination based on pure titanium thinfilm resistors integrated into coplanar waveguide (CPW) structures. The terminated transmission lines exhibit good impedance matching, with simulated reflection coefficients below -20 dB over 100 GHz bandwidth and experimentally measured reflections below -10 dB up to 65 GHz. Additional measurements evaluate the stability and power-handling behavior of the Ti resistors. The results show that thin-film titanium can operate as an effective on-chip RF termination in integrated CPW structures, maintaining stable RF performance over repeated measurements. Such terminations are relevant for high-speed photonic platforms where compact integration and reduced packaging complexity are desirable, including dense modulator architectures.
Wavefront coding technology employs a phase mask to modulate the phase of incident light, thereby dispersing the laser spot on the detector and achieving laser protection for optical systems. Current research has predominantly concentrated on validating laser damage at a single imaging distance, neglecting the evolution of protective capability across varying distances in the wavefront coding imaging system. To address this limitation, this study establishes a wavefront coding imaging system based on a cubic phase function and experimentally elucidates the variation of laser suppression capacity with transmission distance. Under conditions of pulsed laser-induced point damage in the visible spectrum, a strong correlation is observed between the laser suppression ratio and the laser damage threshold improvement value. Additionally, the NAFNet model is utilized to restore encoded images, resulting in high-fidelity reconstruction. The PSNR for both simulated and experimentally decoded images consistently surpasses 23 dB. Furthermore, under laser irradiation conditions, the model adeptly eliminates laser artifacts and recovers image content. This study possesses considerable practical value for the design and implementation of laser protection mechanisms in optical systems.
Cardiomyopathies are often characterized by significant fibrotic remodelling of the heart, marked by an abnormal accumulation of collagen type I. Label free Raman spectroscopy, a non-invasive diagnostic technique, holds promise for monitoring biochemical changes throughout the initiation and progression of different diseases, including cardiomyopathies. This study demonstrates the effectiveness of 70% glycerol as a hyperosmotic immersion liquid for in-depth controlling the optical properties of ex vivo myocardium tissue during deep-UV Raman spectroscopy with 244 nm excitation. The results revealed a considerable enhancement in the intensities of Raman peak, particularly the amide I region after glycerol treatment. This occurred across all depths (0-120 & micro;m) and glycerol treatment durations (30 and 60 min). A noticeable enhancement of the Raman peak at 1647 cm-1 was also observed that is attributable to structural transformations of the collagen due to the dehydration induced by glycerol. This finding suggest that deep-UV Raman can be employed as a specific probe of the collagen environment. As the amide I region reflects structural changes in collagen type I, these findings propose the potential of deep-UV Raman spectroscopy in combination with glycerol as optical clearing agent for monitoring collagen modifications.
All-perovskite tandem solar cells are a promising photovoltaic technology, but their efficiency is strongly limited by the tunnel junction. The tunnel junction enables carrier tunneling and recombination, which depend on the interfacial band alignment. Through quantitative simulations using Silvaco Technology Computer Aided Design (TCAD), we find that hole tunneling is intrinsically more difficult than electron tunneling in the tunnel junction. Efficient tunnel junctions require minimizing the barrier for holes while maintaining a moderate barrier for electrons to balance tunneling. For the SnO2/met-al/PEDOT:PSS tunnel junction in all-perovskite tandem solar cells, tuning the metal work function achieves balanced electron and hole tunneling, reduces junction resistance, and directly enhances performance of tandem solar cells. This work provides quantitative design rules for tunnel junction optimization, offering a clear pathway toward high-performance allperovskite tandem solar cells.
