飞秒激光湿法刻蚀微纳制造

飞秒激光微加工作为一种新型微纳制造技术,在复杂三维构型制作方面具有其独特的优势,但激光加工效率问题严重制约了飞秒激光微加工技术走向实际工程应用,提出一种飞秒激光湿法刻蚀微纳制造方法,以提高飞秒激光微加工的效率为突破口,通过调控激光与物质相互作用获得材料的目标靶向改性,进而结合化学湿法刻蚀实现硬质材料上的高效和高精度三维微加工,采用这一方法制作出的微透镜尺寸为80 m,球冠高6.7 m,表面粗糙度小于10 nm。利用这种方法,实现了不同结构与特性的高质量微透镜阵列的超精密制备,在石英内部也实现了螺旋微通道的复杂三维结构,螺旋通道直径为20 m,长径比超过100。     

Fabrication of microfluidics structures on different glasses by simplified imprinting technique

Imprinting technique is an efficient method for fabricating microstructures for microfluidics and lab-on-chip applications. However such technique is not commonly used for glass based microstructures fabrication. In this study, microstructures were transferred completely and successfully from a nickel alloy stamp to different glasses such as sodalime glass, Pyrex glass, SGBN glass and magneto optical glasses, using imprinting technique. Furthermore, the traditional vacuum hot press for imprinting was replaced with the conventional electric furnace which increases the cost efficiency and simplicity greatly. Using specific mold in the conventional furnace, the mass production of microstructured glass chips can be realized.     

Microstructure array on Si and SiOx generated by micro-contact printing, wet chemical etching and reactive ion etching

A method, combining micro-contact printing (μCP), wet chemical etching and reactive ion etching (RIE), is reported to fabricate microstructures on Si and SiOx. Positive and negative structures were generated based on different stamps used for μCP. The reproducibility of the obtained microstructures shows the methodology reported herein could be useful in Micro-Electro-Mechanical Systems (MEMS), optical and biological sensing applications.     

Large Scale Integrated Photonics for Twenty-First Century Information Technologies

In this paper, we will review research done by the Large-Scale Integrated Photonics group at HP Laboratories, and in particular we will discuss applications of optical resonances in dielectric microstructures and nanostructures to future classical and quantum information technologies. Our goal is to scale photonic technologies over the next decade in much the same way as electronics over the past five, thereby establishing a Moore’s Law for optics.     

Mesoscopic transport equations and contemporary thermodynamics: an introduction

The local equilibrium hypothesis is a very successful basis for non-equilibrium thermodynamics over a wide range of phenomena and physical situations. However, the increasing interest in small systems in nanotechnology, in rarefied gases in high-altitude aeronautics, in high-frequency behaviour in information processing, or the search for new materials with sophisticated internal microstructures and tailored thermal properties have led one to ask about the limits of validity of this hypothesis, and to go beyond it. Here we do so in a constructive way, i.e. not only pointing out at these limits, but also embedding the local-equilibrium theory in a more general framework which explicitly exhibits these limits and suggests how to go beyond them, in search for a wider range of applications and a deeper understanding of the foundations.     

飞秒激光相干场诱导材料功能微结构

飞秒激光在整个脉冲宽度内具有极好的相干性，因而当从同一光束分出的两束或两束以上的光束时间与空间上实现相互叠加时将会形成强度周期性调制的电磁场．这种周期调制的电磁场与材料产生相互作用，能诱导出相应的周期微结构．最近通过两束或两束以上飞秒激光干涉诱导功能微结构得到了广泛研究．文章综合了国内外飞秒激光研究小组在干涉诱导微结构方面的一些最新成果以及作者在这方面开展的工作，对飞秒激光干涉技术的原理及其在诱导微结构方面的应用进行了介绍．     

Investigation of the catalysis and SERS properties of flower-like and hierarchical silver microcrystals

Noble metal nano/microstructures have attracted considerable attention because of their unique properties and their various applications. Controlling the shape of noble metal nano/microstructures is a promising strategy to tailor their physical and chemical properties for various applications in fields such as biological labeling and imaging, catalysis, and sensing. Among various specific structures, flower-like and hierarchical silver nano/microstructures have attracted increasing interest because exploration of these novel nano/microstructures with unusual optical properties can provide new perspectives into the rational design of novel materials. It is significantly more challenging to develop facile and effective solution approaches for systematic manipulation of the shape of Ag nano/microstructures. In this article, we revisited the ascorbic acid reduction method to prepare flower-like silver microcrystal with plate petals and hierarchical Ag microcrystal on a large scale and in high purity. Ascorbic acid plays two roles of a reducing agent and a crystal growth regulator. Therefore, the molar ratio of ascorbic acid and silver nitrate is critical to the formation of Ag microcrystal. The controlling of the two different Ag microstructures can be achieved by adjusting the molar ratio of the reactants in aqueous medium at room temperature. The as-prepared Ag microcrystals were characterized by transmission electron microscopy, scanning electron microscopy, and X-ray diffraction. The flower-like Ag microcrystal with plate petals and hierarchical Ag microcrystal with nanoscale sharp tips and gaps could exhibit high catalytic activity and strong surface-enhanced Raman spectroscopy (SERS) activity due to the high surface area and the local electromagnetic field intensity enhancement, respectively. The potential application of the as-prepared Ag microcrystals in catalysis and SERS was investigated, which revealed that these two kinds of Ag microcrystals exhibit high catalytic activities to the NaBH₄-catalyzed reduction of 4-nitrophenol and significant SERS effect to 4-aminothiophenol molecular due to their nanoscale sharp tips and gaps. Therefore, the flower-like Ag microcrystal and hierarchical Ag microcrystal investigated here could be promising candidates for single particle catalyst and SERS.     

Microtextures Induced by Nanosecond Laser on Ni–Co Alloy Coatings

Ni–Co alloys have a wide range of applications in various fields owning to their excellent physical, chemical, and mechanical properties. In this paper, we prepare Ni–Co alloy coatings on 316L stain steel surfaces by electroplating. We present a novel approach utilizing a nanosecond laser to induce microtextures on Ni–Co alloy coatings. We study experimentally the effects of laser power and scanning rate on the surface morphologies of Ni–Co alloy coatings. The results indicate that the shape and size of induced microtextures can be controlled by the laser power and scanning rate. The size of grains increases with increase in the work current of the laser (WCL) at a certain scanning rate. With the WCL constant, the size of grains decreases with increase in scanning rate while their average height increases. It is a simple and easily-controlled method for the fabrication of microstructures on Ni–Co alloy coatings, which has promising applications in investigations of the properties of microtextured surfaces, such as friction, adhesion, and wetting.     

Light-guide plate using periodical and single-sized microstructures to create a uniform backlight system

Light-guide plates (LGPs) with aperiodic or size-varied microstructures are widely used in edge-lit light-source backlight systems for their high uniformity. In this Letter we designed a LGP with periodic and single-sized microstructures and analyzed the relationship between the holistic arrangement density of the microstructures and the uniformity. By controlling the holistic arrangement density of the microstructures, the uniformity could also be increased.     

Projection ablation of glass-based single and arrayed microstructures using excimer laser

Ablation of single and arrayed microstructures using an excimer laser is studied. The single feature microstructures are fabricated for evaluating the ablation mechanism, threshold fluence, and associated material removing (ablation) rate. The morphology changes during ablation are investigated with the focus on the formation of the ablation defects, debris or recast. The possibility of removing these defects is also evaluated and demonstrated. The present study concentrates on the borosilicate glass, although ablation of polyimide and silicon are performed and discussed for comparison. Polyimide and silicon are the most popular polymer or semiconductor material used in the electronics industry. The arrayed microstructures are ablated to demonstrate the fact that, by repetition of a simple-patterned mask associated with synchronized laser pulses and substrate movement, arrayed and more complex structures can be cost-effectively manufactured. The potential applications of these arrayed microstructures are discussed and illustrated. A low-cost replication technique that uses the arrayed microstructure presently machined as the forming mold for making electroforming nickel microneedles is specifically presented. Finally, the potential areas of using excimer laser in micromachining of glass-based structures for future research are also briefly covered.     

Magnetic force microscopy applied in magnetic data storage technology

Microstructured thin-film elements with critical dimensions of 1 μm or less play an increasingly important role in magnetic components for information technology applications. Devices that are directly based on such microstructures are key components in magnetoelectronics for storage and sensor applications as well as modern concepts which are likely to substitute today’s hard disk drives. Basic research on magnetic materials as well as industrial applications create an increasing demand for high-resolution magnetic imaging methods. One such method is magnetic force microscopy (MFM). In spite of considerable achievements, MFM also has some serious shortcomings, which have not been overcome to date. Under normal circumstances, the method yields only qualitative information about the magnetic object and it is difficult to improve the resolution to values below 100 nm. In this paper, we will report on advanced MFM probe preparation, based on electron beam methods, and discuss the possibilities for batch fabrication of such advanced MFM tips. We show that the advanced probes allow high-resolution imaging of fine magnetic structures within thin-film permalloy elements without perturbing them. Additionally, we present high-frequency MFM measurements on a hard disk write head. Received: 2 September 2002 / Accepted: 2 September 2002 / Published online: 5 March 2003 RID="*" ID="*"Corresponding author. Fax: +49-681/302-3790, E-mail: m.koblischka@mx.uni-saarland.de     

Facile fabrication of superhydrophobic polytetrafluoroethylene surface by cold pressing and sintering

A series of superhydrophobic polytetrafluoroethylene (PTFE) surfaces were prepared by a facile cold pressing and sintering method, and their microstructures and wetting behaviors could be artificially tailored by altering sintering temperature and using different masks. Specifically, the microstructures mainly depended on the sintering temperature, whereas the wetting behaviors, water contact angle (WCA) and sliding angle (SA), greatly hinged on both the sintering temperature and mask. Then a preferable superhydrophobic surface with WCA of 162 ± 2° and SA of 7° could be obtained when the sintering temperature was 360 °C and the 1000 grit abrasive paper was used as a mask. In addition, it was worth noting that the as-prepared surfaces exhibited excellent stability under UV illumination, which was the most key factor for them toward practical applications.     

Giant enhancement of photoluminescence emission in monolayer WS2 by femtosecond laser irradiation

Monolayer transition metal dichalcogenides have emerged as promising mat erials for opt oelectTonic and nanophotonic devices.However,the low photoluminescence(PL)quantum yield(QY)hinders their various potential applications.Here we engineer and enhance the PL intensity of monolayer WS₂by femtosecond laser irradiation.More than two orders of magnitude enhancement of PL intensity as compared to the as-prepared sample is determined.Furthermore,the engineering time is shortened by three orders of magnitude as compared to the improvement of PL intensity by continuous-wave laser irradiation.Based on the evolution of PL spectra,we attribute the giant PL enhancement to the conversion from trion emission to exciton,as well as the improvement of the QY when exciton and trion are localized to the new-formed defects.We have created microstructures on the monolayer WS₂based on the enhancement of PL intensity,where the engineered structures can be stably stored for more than three years.This flexible approach with the feature of excellent long-term storage stability is promising for applications in information storage,display technology,and opto electronic devices.     

Femtosecond laser-induced mesoporous structures on silicon surface

By femtosecond laser line-by-line scanning irradiating, large-scale microstructures were formed on the surface of silicon with dimensions of 1 × 1 mm². Scanning electron microscope investigations exhibited that homogeneous surface microstructures, such as directional-arranged bacilliform mesoporous structures, have been successfully prepared. The dependence of the surface morphology on laser pulse energy was analyzed, and the results indicated that the bacilliform mesoporous structures only can be textured within a certain energy range. The optical reflective spectrum measurement revealed that the presence of bacilliform mesoporous structures can significantly enhance the absorptivity of silicon at visible light range. This work would help to control the formation of surface micro/nanostructures on silicon and other materials, which has potential applications in solar energy, photoelectronics, biology and material science.     

Fabrication methods of 3D periodic metallic nano/microstructures for photonics applications

Periodic metallic nano/microstructures have received a great a deal of attention in the photonics research community over the last few decades due to their intriguing optical properties. Three‐dimensional metallic nano/microstructures such as metallic photonic crystals, metamaterials, and plasmonic devices possess unique characteristics of tailored thermal radiation, negative refraction and deep subwavelength confinement of light. In this article, the recent progress on the experimental methods for the realisation of three‐dimensional periodic metallic and thin metal film coated dielectric nano/microstructures operating from optical to mid‐infrared frequencies has been reviewed. Advancement of the state‐of‐the‐art nanofabrication methods over the last few decades have led to the development of metallic nano/microstructures of diverse geometries, high resolution features and large scale production. The recent progress in the novel fabrication methods have inspired the development of functional and exciting photonic devices based on periodic metallic nano/microstructures with various applications in photonics including communications, photovoltaics, and biophotonics.     

Optical spin-dependent angular shift in structured metamaterials

The physics behind the spin (polarization)-dependent electromagnetic hot-spot phenomenon is due to the presence of the geometric phase resulting from the optical spin-orbit interaction in the interaction of light with the subwavelength microstructures. Unlike the tiny spin-dependent shift of light associated with the usual spin-Hall effect of light, here we present the distinct polarization-dependent angular shift by employing an array of subwavelength metallic apertures. More importantly, this novel electromagnetic precession is accompanied by the extraordinary optical transmission phenomenon and offers the exciting possibilities for novel applications for subwavelength structured metallic systems.     

Selective ablation-assisted two-photon stereolithography for effective nano- and microfabrication

The two-photon stereolithography (TPS) process has strong merits for the direct fabrication of 2-D and 3-D microstructures with sub-100-nm resolution. In this paper, we report an effective fabrication process in which selective ablation-assisted TPS (SA-TPS) was used to ameliorate some of the limitations of the TPS process. In SA-TPS, two processes (namely, an additive process of two-photon induced photocuring and a subtractive process of selective laser ablation) were performed sequentially using a single femtosecond laser optical scanning system. The effectiveness of the proposed process was demonstrated in several applications, including precise high-resolution patterning at resolution levels higher than those achievable using the TPS process, and the fabrication of structures with high mechanical sensitivity.     

Single-step synthesis of wrinkled MoSe2 thin films

Controlled and simple synthesis strategy of two-dimensional (2D) nanomaterials is critical for designing the related heterostructures with different geometries, which influence strain, electronic structures, light-interactions, and surface reactions. Here, we report a single-step growth method for wrinkled MoSe₂ thin films on flat SiO₂/Si substrates by using high-vacuum co-evaporation. Above the critical film thickness of 15–20?nm, the MoSe₂ films start to form wrinkled structure with lateral periodicity of 7–10?μm, which significantly reduces light reflectance in the visible range. We demonstrate formation of the wrinkled pattern on the selective area either by etching the substrate surface or by depositing gold films. In addition, we observe switching of the microscopic growth mode from a layered stacking to a vertically aligned growth, which results in 2D-3D hybrid microstructures. Our single-step synthesis approach might be generalized to obtain wrinkled 2D-3D hybrid nanomaterials and utilized for flexible electronic & optoelectronic devices, efficient solar cells, catalytic electrodes, and anti-counterfeiting applications.     

Fabrication of micro-gratings on Au-Cr thin film by femtosecond laser interference with different pulse durations

We encoded surface relief micro-gratings on Au-Cr thin films using two-beam interference of femtosecond laser pulses with the durations from 25 fs to 70 fs. The dependence of the fabrication quality on the pulse duration has been investigated both numerically and experimentally. The results revealed that the shorter pulses were preferable to prepare periodical microstructures with minimal ablation fringe width and satisfied fabrication quality. This work has potential applications on periodic functional microstructures fabrication for ultra-fine processing and modification on various materials, especially for intractable materials.