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Lithium niobate (LN) crystal with anti‐reflective subwavelength structures (ASSs) has great applications in high‐power tunable optical parametric oscillator (OPO) lasers. However, it is still a great challenge to 3D nanofabrication of LN ASSs. Herein, a wet‐etching‐assisted laser polarization domain inversion (WE‐LPDI) technology is proposed to fabricate periodic cone arrays with a period from 200 nm to 4 µm on LN. Based on the optimized structural parameters, large‐area LN ASSs with a period of 1.3 µm and a height of 1.7 µm were fabricated on LN, which exhibits an average transmittance of 3–5 µm increasing from 78% to 85% and a highest transmittance of 88% at 5 µm. It has been demonstrated that the LN ASSs show high stability under high‐temperature and high‐power laser irradiation, which shows potential applications for high‐power mid‐IR lasers. The results indicate that the WE‐LPDI technology provides a novel way for 3D nanofabrication of LN. [ABSTRACT FROM AUTHOR]

Intrinsic silicon (Si) is forbidden for infrared (IR) sensing at the communication wavelength like 1.31 or 1.55 µm due to the well‐known bandgap limitation. In this work, an unexpected physical picture of using argon (Ar) is identified, which is usually inert to the surrounding chemical environment and used as a protective agent in semiconductor processing, to overcome the IR‐sensing‐forbidden problem in Si. Here, it is shown by an analysis of a dynamic secondary ion mass spectrometer that such a Si, when exposed to laser pulse in Ar gas, can contain a very high dose of Ar up to 1020 cm−3 even after 1300 days. First‐principles calculations, molecular dynamics, and Hall effect measurements reveal that, due to both steric and dynamic repulsions by Ar orbitals to Si dangling bonds, the Ar‐filled‐vacancy produces a much wider defect band inside the gap, which is not only responsible for strong infrared absorption, but also causes a significant increase in n‐type conductivity, both in line with experiments. The study proves that originally inert elements in fact can act as active impurities in semiconductors for advanced applications, which updates the current knowledge of defect physics. [ABSTRACT FROM AUTHOR]

Functionalized optical fiber tips featuring miniature sizes and diverse functions have broken the limitations of traditional optical fiber with fixed shapes and single materials, significantly enriching the application scenarios in communication, sensing, imaging, and other fields. However, the unconventional shape presents challenges in manufacturing arbitrarily sophisticated 3D micro/nano structures on optical fiber tips. Femtosecond laser 3D nano‐printing (FL‐3DNp) technology injects new vitality into the functionalization of fiber tips due to its high‐precision, customizable structure, and real 3D processing abilities, as well as advantages of non‐vacuum, maskless, and plentiful materials. This paper extensively compares the key performance parameters of various micro‐nano manufacturing technologies for functionalizing optical fiber probes and focuses on the FL‐3DNp technology. In addition, the latest research progresses are systematically presented from the perspective of structure and application. Finally, the current research challenges and future development directions in this emerging field are discussed, aiming at providing scientific and industrial guidance for FL‐3DNp in functionalizing optical fibers. [ABSTRACT FROM AUTHOR]

Micro‐optical components exhibit significant potential applications in various fields such as imaging, optical fiber communication, and aerospace owing to their small size, light weight, and flexible design. It is imperative to fabricate micro‐optical components on hard brittle materials to improve stability and broaden the optical transmission range. Therefore, femtosecond laser processing technology is demonstrated to be an efficient processing strategy for preparing refractive/diffractive micro‐optical components on hard brittle materials compared to other established micromachining techniques. This study reviews recent advances in refractive/diffractive micro‐optical components using femtosecond laser processing technologies. The applications of refractive/diffractive micro‐optical components with high accuracy, efficiency, and quality in the fields of imaging, sensing, display, and integration are also summarized. Moreover, the challenges of femtosecond laser processing technologies and the outlook of micro‐optical components are highlighted. [ABSTRACT FROM AUTHOR]

Optical crystals are ideal materials for complex functional and durable optical components, but their good stability and hardness bring about difficulties in high‐precision machining and require surface roughness below λ/10. Femtosecond laser ablation is a widely applicable processing method indifferent to material types, but its 3D fabrication capability is limited by the accumulation of ablated debris and rough ablated surface. This work demonstrates a universal and flexible technology for the fabrication of crystalline micro‐optics with required shape and surface roughness for the most demanding optical phase control. The cavitation‐assisted ablation by a direct laser writing mode is followed by a high‐temperature treatment to remove the rough non‐crystalline layer caused by ablation. The annealing at temperatures below the melting point of the crystal reduces the roughness down to ≈2 nm without changing the structure shape. This virtue of maintaining the designed shape without change, which is impossible during thermal morphing of 3D surfaces of glasses, allows for a previously unavailable flexibility of surface finish for the most demanding optical micro‐optical elements made in this study. This universal technology with nanoscale resolution and free‐form 3D manufacturing capability is applicable for various crystals and provides a new way to fabricate micro‐/integrated‐optics and nonlinear optical elements. [ABSTRACT FROM AUTHOR]

Soft robots controlled by different actuation schemes are flourishing owing to the continued development of smart materials. However, most of the existing actuators are powered by a single source with predetermined mechanical properties and motion characteristics. Speed, power, and efficiency of these actuators are thus far inferior to their conventional counter parts. How to preload or alter the internal energy distribution and trigger rapid kinetic energy release combined with re‐programmability is a challenge and corresponding solutions will extend the practical use of soft robotics. Herein, a hybrid magnetically and photothermally responsive actuator with high degrees of freedom by using a coupled‐field manipulation strategy is proposed. As a proof‐of‐concept, a crab robot (CraBot) that contains uniformly distributed superparamagnetic particles and localized light‐responsive joints is produced. The spatial magnetic field exerts force on the robot, leading to real‐time adjustment of energy distribution within the entire robot. Meanwhile, the focused light field enables selective deformation of specific joints, releasing the accumulated energy into kinetic energy of motion for quick actuation. The directional accumulation and addressable release of elastic energy enables the CraBot to walk efficiently with improved power and speed. Such a hybrid‐field manipulation strategy holds great promise for sophisticated actuation of soft robots. [ABSTRACT FROM AUTHOR]

Thin, lightweight micro‐diffractive optical elements (M‐DOEs) are of great significance to integrated optics. However, the narrow working bandwidth of M‐DOEs allows them to operate only at specific wavelengths. Existing solutions require multiple components assembly, which is difficult to implement in an integrated system. Here, a general designing and processing scheme of an optofluidic‐integrated broad‐bandwidth M‐DOE is reported, achieving an average diffraction efficiency of over 84% across the entire visible band (406–824 nm). As a proof‐of‐concept, a wideband operating micro‐diffractive lens and orbital angular momentum beam micro‐generator are demonstrated. This strategy provides a common protocol for various broad‐bandwidth M‐DOEs operating in integrated optical systems. [ABSTRACT FROM AUTHOR]

Abstract: Actuators that can convert environmental stimuli into mechanical work are widely used in intelligent systems, robots, and micromechanics. To produce robust and sensitive actuators of different scales, efforts are devoted to developing effective actuating schemes and functional materials for actuator design. Carbon‐based nanomaterials have emerged as preferred candidates for different actuating systems because of their low cost, ease of processing, mechanical strength, and excellent physical/chemical properties. Especially, due to their excellent photothermal activity, which includes both optical absorption and thermal conductivities, carbon‐based materials have shown great potential for use in photothermal actuators. Herein, the recent advances in photothermal actuators based on various carbon allotropes, including graphite, carbon nanotubes, amorphous carbon, graphene and its derivatives, are reviewed. Different photothermal actuating schemes, including photothermal effect–induced expansion, desorption, phase change, surface tension gradient creation, and actuation under magnetic levitation, are summarized, and the light‐to‐heat and heat‐to‐work conversion mechanisms are discussed. Carbon‐based photothermal actuators that feature high light‐to‐work conversion efficiency, mechanical robustness, and noncontact manipulation hold great promise for future autonomous systems. [ABSTRACT FROM AUTHOR]

Abstract: The achievement of an ultrastrong coupling regime between surface plasmon modes generated by gold conical pits arrays and excitons associated to squaraine dye is demonstrated. Numerical and experimental steady‐state reflection measurements demonstrate a remarkable Rabi splitting of 860 meV, to date the largest reported value involving surface plasmon modes. Furthermore, the dynamics of the hybrid states under the ultrastrong coupling regime is investigated by transient absorption spectroscopy. The results show that the upper bands are too short‐lived to be detected, while the lower bands have a relatively shorter lifetime with respect to the bleaching recovery of pure squaraine dye. This result contradicts the behaviour of systems in strong coupling regimes, suggesting a different photophysics between strong and ultrastrong coupled systems. [ABSTRACT FROM AUTHOR]

This paper demonstrates femtosecond laser direct writing mediated flexible integration of plasmonic Ag/Pd alloy nanostructures that can be potentially used as a robust surface‐enhanced Raman spectroscopy substrate inside the microfluidic chip. Silver–palladium alloy with controllable composition ratio can be patterned into plasmonic nanostructures due to two‐photon absorption induced coreduction of silver/palladium double metal ions. Since the alloy structures can effectively protect the silver from oxidation, thus they can facilitate the stable on‐chip detection devices with long lifetime. The as‐fabricated silver–palladium alloy substrate with 18% content of palladium maintains a relatively high enhancement factor of about 2.62 × 108 while at the same time demonstrating the best stability against aerobic oxidation, as it is stable for up to 20 d under ambient aerobic conditions, exhibiting a significant improvement compared to those unprotected silver substrates which have a limited lifetime of only 3 or 4 d. [ABSTRACT FROM AUTHOR]

Femtosecond laser machining has been widely used for fabricating arbitrary 2.5 dimensional (2.5D) structures. However, it suffers from the problems of low fabrication efficiency and high surface roughness when processing hard materials. To solve these problems, we propose a dry-etching-assisted femtosecond laser machining (DE-FsLM) approach in this paper. The fabrication efficiency could be significantly improved for the formation of complicated 2.5D structures, as the power required for the laser modification of materials is lower than that required for laser ablation. Furthermore, the surface roughness defined by the root-mean-square improved by an order of magnitude because of the flat interfaces of laser-modified regions and untreated areas as well as accurate control during the dry-etching process. As the dry-etching system is compatible with the IC fabrication process, the DE-FsLM technology shows great potential for application in the device integration processing industry. [ABSTRACT FROM AUTHOR]

Hydrogels such as poly(ethylene glycol) diacrylate are a class of cross-linked polymers that have the ability to absorb water and change volume. Here, a humidity responsiveness of hydrogel film fabricated by the photopolymerization of poly(ethylene glycol) diacrylate (PEG-DA) monomer is reported. This kind of film could be driven by a small humidity gradient, thus spontaneous deformation and motion can be achieved by placing the film onto a moist filter paper. The influence factors of humidity response sensitivity such as the exposure time and number-average molecular weight of PEG-DA monomer used during the fabrication are investigated. Under different relative humidity, the film displays different degrees of pink color and the intensities of fluorescence under 365 nm illumination are also different, which renders the film to be used as a 'humidity test strip.' A humidity-driven walking device is fabricated and the walking velocity is about 3 mm min−1 under the actuating water vapor. Vapor of volatile polar solvents could also drive the actuator to achieve fast deformation and shows the variety of the film responsivity. [ABSTRACT FROM AUTHOR]

Multi scale hierarchical structures underpin mechanical, optical, and wettability behavior in nature. Here we present a novel approach which can be used to mimic the natural hierarchical patterns in a quick and easy maskless fabrication. By using two-beam interference lithography with angle-multiplexed exposures and scanning, we have successfully printed large-area complex structures having a cascading resolution and 3D surface profiles. By precisely controlling the exposure dose we have demonstrated a capability to create different 3D textured surfaces having comparable aspect ratio with period spanning from 4 μm to 300 nm (more than one order of magnitude) and the height spanning from 0.9 μm to 40 nm, respectively. Up to three levels of biomimetic hierarchical structures were obtained that show several natural phenomena: superhydrophobicity, iridescence, directionality of reflectivity, and polarization at different colors. [ABSTRACT FROM AUTHOR]

A prototypical hybrid system formed by strong coupled gold hole arrays and J-aggregate molecules is investigated by using both steady-state spectroscopic method and ultrafast pump-probe approach. In particular, the plasmonic response of the device has been tuned by modifying its periodicity thus to achieve the strongest possible coupling regime. It is found that in the transient absorption spectra, under upper band excitation, the bleaching signal from uncoupled J-aggregate molecules completely disappears. Instead, two distinctive period dependent bleaching bands are formed, clearly fingerprint of the hybrid exciton-plasmon state. The dynamics of these bands is also directly analyzed. A remarkable long lifetime is found especially for the upper band, corresponding to the presence of a trap state in its transient absorption spectra under resonance excitation. Such unique feature should provide a new approach to control quantum-mechanical states under coherent coupling. [ABSTRACT FROM AUTHOR]

The article presents a surface texturing and femtosecond laser doping technology for dental implants. A thin layer was predeposited on the surface of titanium and adopted a femtosecond laser to ablate the composite surface. The doping concentration is controllable through the seeded silver layer thickness. The effectiveness of the technology was proved by cytotoxicity, antibacterial and acid aging experiments.

Organic single crystals have attracted great attention because of their advantages of high charge-carrier mobility, high chemical purity, and potential for flexible optoelectronic devices. However, their intrinsic properties of sensitive to organic solvent and fragile result in a difficulty in the fabrication of the organic crystal-based devices. In this work, a simple and non-destructive technique of template stripping is employed to fabricate single-crystal-based organic light-emitting devices (OLEDs). Efficient and uniform carrier injection induced by an improved contact between crystals and both top and bottom electrodes is realized, so that a homogeneous and bright electroluminescence (EL) are obtained. Highly polarized EL and even white emission is also observed. Moreover, the crystal-based OLEDs exhibit good flexibility, and keep stable EL under a small bending radius and after repeated bending. It is expectable that this technique would support broad applications of the organic single crystals in the crystal-based optoelectronic devices. [ABSTRACT FROM AUTHOR]

Micronanofabrication technologies developed so far pursue faithful conversion from digital models to matter structures. This is vital for microdevices in optics, mechanics, and electronics, where device shape and size matter. However, biotissues grow under rich environmental factor interactions, as demands novel manufacturing approaches for biomimetic and biological fabrication. Here, a concept of dynamic laser prototyping is reported, which is based on a new finding of a multilayered three-dimensional (3D) wrinkling phenomenon. The 3D wrinkling started with formation of a photocrosslinked hydrogel sheet by femtosecond laser direct writing. It was followed by spontaneous self-bending of the sheet, caused by a purposely designed sheet-substrate stress mismatch. The flower blooming process has been successfully mimicked, indicating broader usages of the technology in biotissue-growth-related manufacturing. [ABSTRACT FROM AUTHOR]

The small field‐of‐view (FOV) limits the range of vision in various detecting/imaging devices from biological microscopes to commercial cameras and military radar. To date, imaging with FOV over 90° has been realized with fish‐eye lenses, catadioptric lens, and rotating cameras. However, these devices suffer from inherent imaging distortion and require multiple bulky elements. Inspired by compound eyes found in nature, here a small‐size (84 μm), distortion‐free, wide‐FOV imaging system is presented via an advanced 3D artificial eye architecture. The 3D artificial eye structure is accomplished by exploiting an effective optical strategy — high‐speed voxel‐modulation laser scanning (HVLS). The eye features a hexagonal shape, high fill factor (FF) (100%), large numerical aperture (NA) (0.4), ultralow surface roughness (2.5 nm) and aspherical profile, which provides high uniformity optics (error < ±6%) and constant resolution (FWHM = 1.7 ± 0.1 μm) in all directions. Quantitative measurement shows the eye reduces imaging distortion by two/three times under 30°/45° incidence, compared with a single lens. The distortion‐free FOV can be controlled from 30° to 90°. [ABSTRACT FROM AUTHOR]

Reported here is a bioinspired fabrication of superhydrophobic graphene surfaces by means of two-beam laser interference (TBLI) treatment of graphene oxide (GO) films. Microscale grating-like structures with tunable periods and additional nanoscale roughness are readily created on graphene films due to laser induced ablation effect. Synchronously, abundant hydrophilic oxygen-containing groups (OCGs) on GO sheets can be drastically removed after TBLI treatment, which lower its surface energy significantly. The synergistic effect of micro-nanostructuring and the OCGs removal endows the resultant graphene films with unique superhydrophobicity. Additionally, dual TBLI treatment with 90° rotation is implemented to fabricate superhydrophobic graphene films with two-dimensional grating-like structures that can effectively avoid the anisotropic hydrophobicity originated from the grooved structures. Moreover, the superhydrophobic graphene films become conductive due to the laser reduction effect. Unique optical characteristics including transmission diffraction and brilliant structural color are also observed due to the presence of periodic microstructures. As a mask-free, chemical-free, and cost-effective method, the TBLI processing of GO may open up a new way to biomimetic graphene surfaces, and thus hold great promise for the development of novel graphene-based microdevices. [ABSTRACT FROM AUTHOR]

Recently great progress has been achieved in highly effective hybrid solar cells fabricated using aqueous materials. The state-of-the-art energy conversion efficiency has been close to 5% with high photocurrent. However, charge separation and transport mechanism in the aqueous-processed hybrid solar cells are rarely reported and are usually assumed to be similar to oil-phase processed systems; that is, self-assembly polymers are mainly responsible for charge separation and carrier transport. To date, this assumption has prohibited further improvement of the conversion efficiency in aqueous-processed hybrid systems by adopting any appropriate technique routes. Here, ultrafast carrier dynamics in these hybrid solar cells consisting of poly( p-phenylenevinylene) (PPV)-based aqueous polymers and water-solution CdTe nanocrystals (NCs) are investigated in detail. Self-charge separation in grown CdTe NC partly capped CdS shell layers after anneal treatment is unambiguously identified. Different from their oil-soluble counterparts, these core/shell nanocrystals do not have the restrictions of quantum confinement and surface ligands, form effective charge transport networks, and play a dominant role in the charge separation and carrier transport processes. These findings provide a greater understanding on the fundamental photophysics in aqueous-processed hybrid systems. [ABSTRACT FROM AUTHOR]

In view of mass‐production and solution‐processing capabilities, graphene oxides (GOs), generally prepared by chemical oxidation of graphite and subsequent exfoliation in aqueous solution, are widely used as an effective route to graphene‐like materials. However, the oxygen‐containing groups (OCGs) on the graphene sheets make GO insulating, which significantly restricts its applications, especially for electronics. Therefore, reduction methods that are used to remove OCGs become critical. In recent years, in addition to thermal and chemical reduction, photoreduction has emerged as an appealing alternative because photoreduction does not rely on either high temperature or toxic chemicals. In this progress report, the recent development of the photoreduction of GOs and their unique properties are highlighted, as well as their related applications. Photoreduction strategies including photothermal reduction, catalytic/catalyst‐free photochemical reduction, and solid state/in‐solution laser reduction are summarized. Moreover, photoreduction of GO permits exquisite control over film conductivities, residual oxygen contents, porosity, and surface wettability, which lead to various functionalities towards a wide range of applications, such as field‐effect‐transistors (FETs), flexible electrodes, sensors, supercapacitors, Li‐ion batteries, photovoltaic devices, and photocatalysis. It is anticipated that, with the rapid progress of photoreduction methodology, GOs would be more competitive in the graphene‐oriented applications. [ABSTRACT FROM AUTHOR]

Organic single-crystalline materials have attracted great attention for laser applications. However, the fabrication of laser resonators and pattern of crystals are still intractable problems. Organic single crystals have been limited to fundamental property studies despite their superior photonic characteristics. In this work, whispering-gallery mode (WGM) resonators of BP1T and BP2T crystalline materials have been fabricated through a combination method with improved lithography and dry etching. Crystalline microresonators with different geometries over a large area are top-down fabricated with submicrometer spatial resolution. WGM lasing oscillation from circular, hexagonal, pentagonal and square resonators is definitively observed. The BP1T and BP2T crystals are characterized with high refractive index, and stable lasing in aqueous solution is demonstrated besides in the air environment. It is expected that organic crystalline materials would be used for the practical applications in a variety of organic electronic and optical devices. [ABSTRACT FROM AUTHOR]

Graphene quantum dots (GQDs) have recently emerged as a promising type of low‐toxicity, high‐biocompatibility, and chemically inert fluorescence probe with a high resistance to photobleaching. They are a prospective substitution for organic materials in light‐emitting devices (LED), enabling the predicted concept of much brighter and more robust carbon LED (CLED). However, the mechanism of GQD emission remains an open problem despite extensive studies conducted so far, which is becoming the greatest obstacle in the route of technical improvement of GQD quantum efficiency. This problem is solved by the combined usage of femtosecond transient absorption spectroscopy and femtosecond time‐resolved fluorescence dynamics measured by a fluorescence upconversion technique, as well as a nanosecond time‐correlated single‐photon counting technique. A fluorescence emission‐associated dark intrinsic state due to the quantum confinement of in‐plane functional groups is found in green‐fluorescence graphene quantum dots by the ultrafast dynamics study, and the two characteristic fluorescence peaks that appear in all samples are attributed to independent molecule‐like states. This finding establishes the correlation between the quantum confinement effect and molecule‐like emission in the unique green‐fluorescence graphene quantum dots, and may lead to innovative technologies of GQD fluorescence enhancement, as well as its broad industrial application. [ABSTRACT FROM AUTHOR]

Topological phases of matter, with their quantized invariants, offer the potential for disorder‐resistant transport via topological bound states. Contrary to the belief that dissipation disrupts Hermiticity and Zak phase quantization, theoretical and experimental evidence of their persistence in a non‐Hermitian photonic waveguide array is presented. A three‐layer Su‐Schrieffer‐Heeger (SSH) chain is demonstrated, which can be split into a Hermitian SSH subspace and a non‐Hermitian ladder subspace through hidden symmetry. This division allows the SSH subspace to retain its topological properties, resulting in a quantized Zak phase and lossless topological bound states. Additionally, the non‐Hermitian subspace supports coherent transport dynamics, with the phase and intensity of bound states fixed at two extreme SSH layers, confirming the presence of the Hermitian subspace. These findings enhance the understanding of the interplay between non‐Hermiticity and topology and pave the way for coherent topological light transport. [ABSTRACT FROM AUTHOR]

Strong similarities for relativistic electrons stimulated from electron beams and electron clouds are merging the boundary of wave‐particle duality of electrons, one of which being superposition is Cherenkov radiations. Recent theoretical investigations into quantum Cherenkov effects for cone‐shape particles have hypothesized electron‐spin flip transitions in bound‐ and free‐electron systems like bulk silica and graphene. However, experimental validation of these predictions remains outstanding. Here, analogous phenomena of polariton‐version quantum Cherenkov radiations observed by broadband femtosecond pump‐probe experiments is reported, and demonstrate double‐cone emission processes involving of Cherenkov‐type phonon polaritons (PhPs) and plasmon‐PhPs in ultrashort‐pulse‐stimulated ferroelectric crystals and graphene, respectively. Through component analysis of double‐cone polariton emissions using an empirical quantum dynamics model, the initial polariton dynamics are restored by time translation corrections. The resulting quantum wave packets of PhPs are found to be correlated with femtosecond‐laser‐induced modifications inside ferroelectric lithium niobates, achieving a PhP threshold criterion for ultrasmooth femtosecond laser nanofabrication. [ABSTRACT FROM AUTHOR]

Terahertz photonic single‐pole double‐throw (SPDT) switches, which facilitate on‐chip channel control and signal routing, serve as the key components of future terahertz communication and sensing systems. However, broadband and low‐loss on‐chip photonic SPDT switches still present a formidable challenge due to the restricted capability of manipulating terahertz waves in photonic circuits. Here, a non‐Hermitian loss‐driven solution is proposed for achieving broadband and low‐loss terahertz on‐chip photonic SPDT switches. As proof of concept, an all‐silicon terahertz SPDT switching chip is experimentally demonstrated around the center frequency of 125 GHz with a relative bandwidth of 7.2%. The two paths are driven by external optical pumping and evolve adiabatically around an exceptional point (EP) in the unbroken and broken PT‐symmetric phases. Interestingly, the strong non‐Hermitian loss instead enforces the photonic modes to the low‐loss energy level and thereby keeps the switch working at the low‐loss transmission status. As a result, the minimum optical powers require for the ultrafast terahertz communications are only −2 and 1 dBm. Both channels of the SPDT switch support on‐chip 16‐QAM streams with a 36‐Gbit s−1 data rate. The design as a basic building block is anticipated for a myriad of on‐chip applications, including 6G communications, detection, and sensing. [ABSTRACT FROM AUTHOR]

Manipulating photons in quantum photonic integrated circuits (QPICs) is essential for quantum communications and computation, demanding precise control over phase shifts and photon coupling. Despite the challenges arising from the low electro‐optic and thermo‐optic coefficients of glass waveguides, femtosecond laser direct writing (FsLDW) technology offers a rapid method for QPIC preparation. In this work, the use of auxiliary fields is proposed to reconfigure QPICs with FsLDW. Through adiabatic elimination, modulations of inter‐waveguide coupling are achieved, allowing for arbitrary, controllable beam‐splitting ratios and error correction in discrete quantum walking networks. The experiments also demonstrate full‐period phase shift modulation over 2π in a Mach‐Zehnder interferometer by employing an adjustable auxiliary field. Particularly, high‐quality two‐photon quantum interference and high‐fidelity quantum logic function conversion between a controlled‐NOT gate and a controlled‐PHASE gate are exhibited. This novel approach provides a promising mechanism for modulating the phase and coupling between photons in 3D and large‐scale QPICs. [ABSTRACT FROM AUTHOR]

Stimuli-Responsive Materials: Smart Compound Eyes Enable Tunable Imaging (Adv. Funct. Keywords: compound eyes; femtosecond laser; smart materials; tunable optical components; variable-focus imaging Compound eyes, femtosecond laser, smart materials, tunable optical components, variable-focus imaging. [Extracted from the article]

Compound eyes are natural multiaperture optical imaging systems and have substantial potential in the field of modern optics. However, both natural and artificial compound eyes are composed of ommatidia with fixed focal lengths, and thus incapable of variable‐focus imaging. In this study, inspired by the tunable crystalline lens of human eyes, smart stimuli‐responsive compound eyes based on the bovine serum album (BSA) protein are fabricated via femtosecond laser direct writing. Due to the swelling and shrinking effect of BSA under different pH conditions, a tunable field of view (FOV, 35°–80°) and variable focal length of ommatidia are achieved. In addition to the direct prototyping of an entire protein‐based compound eye, the ability to flexibly integrate the smart protein ommatidia with a conventional optical lens (an SU‐8 lens in this study) to form a composite compound eye is shown. The composite compound eye achieves nearly 400% of focal length tuning at a fixed FOV. It is anticipated that femtosecond laser fabrication and the integration of smart protein‐based compound eyes may emerge as an enabler for fabricating miniature tunable imaging systems. [ABSTRACT FROM AUTHOR]

On‐chip polarization manipulation is proposed via a waveguide that is adiabatically twisted along its longitudinal axis, which can be fundamental building blocks for polarization‐encoded optical communication and information processing. With the help of femtosecond direct laser writing, the polarization rotators for both telecom and visible wavelengths are fabricated, which show polarization conversion efficiencies of >90% at 1550 nm and ≈80% at 646 nm, respectively. Furthermore, a polarization router consisting of multiple waveguides with different twisting angles is demonstrated. With the polarization router, photons with different polarizations are directed to different paths. Based on such platform, the path entanglement between the photons can be transformed to polarization entanglement, which will extend the quantum information technology to higher‐dimensional Hilbert space. [ABSTRACT FROM AUTHOR]

With high thermal and mechanical stability, glass artificial compound eyes have great potential applications in wide field‐of‐view (FOV) imaging and fast detection. However, the rapid fabrication of large‐area, high integration, uniform, and well‐designed three‐dimensional (3D) glass compound eyes is still a great challenge. Here, a dry‐etching‐assisted femtosecond laser machining (DE‐FsLM) technology is proposed for fabrication of cm‐sized concave compound eye from a curved sapphire substrate, with which the fabrication efficiency can be improved by over two orders of magnitude compared with direct laser ablation. With high hardness and thermal stabilities, the sapphire concave compound eyes can be used as high‐temperature and hard‐casting templates for the replication of convex compound eyes on K9 glass. The replicated cm2‐size all‐glass compound eye consists of a spherical macrolens (1 cm diameter and 2.3 mm height) and over 190 000 close‐packed ommatidia (≈20 µm diameter and 1.5 µm height). The compound eyes exhibit excellent optical properties with wide FOV (up to 90°) imaging and focusing. These results indicate that the DE‐FsLM and casting replication technology will open new opportunities in micro‐/nanofabrication of hard materials. [ABSTRACT FROM AUTHOR]

For the simple and versatile fabrication of nanosmooth finished microlens arrays on hard materials, an approach combining femtosecond laser modification with subsequent ion beam etching is demonstrated. This method is based on the dependence of the plasma etching rate on the laser fluence used to modify the surface. The fabricated microlenses exhibit a low surface roughness of approximately 2.5 nm, due to the high precision of the plasma etching and benefit from the smooth interface between the laser‐modified and pristine subsurface regions. Microlenses with focal lengths ranging from 60 to 100 µm are realized by controlling the laser fluence, exposure dose, and etching time. Uniform square and hexagonal microlens arrays are fabricated on both hard and ultrahard materials and glasses (fused silica, GaAs, SiC, diamond) by the same process and deliver high‐quality focusing and imaging. [ABSTRACT FROM AUTHOR]