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1.
Photocurable finishes should be extensively used for industrial wood joinery in the near future even if some technical problems have still to be solved and if the durability of the finishing system has to be enhanced. In a previous work, we studied the curing reaction of acrylic resins containing some particular photoinitiators by photocalorimetry and showed that curing can be achieved under daylight with these compounds (i.e. solving the problem of restoration on site). The aim of this work is to enhance the durability of these systems by incorporating UV absorbers into the formulations. The consequences of such an addition onto the curing kinetics are again investigated by photocalorimetry.  相似文献   
2.
    
Ultrathin lossy films have attracted much attention due to their strong interference persisting inside the lossy dielectric film on a reflective substrate. Here, a plasmon‐enhanced ultrathin film broadband absorber is proposed by combining the ultrathin film absorber with localized surface plasmon resonances. This concept can be realized by patterning nanoholes on an absorber comprised of an absorptive ultrathin Ge film and a reflective Au layer, where the localized surface plasmon mode is activated by metallic pore‐shaped holes. The plasmonic enhancement is resulting from the pore‐shape localized resonance mode, which increases the optical path length through scattering and concentrates the incident light field near the interface of Ge/Au. The experimental characterization results of a nanoporous ultrathin film absorber, which is fabricated with a scalable laser interference lithography approach, demonstrate its superior light absorption performance. Several materials, such as Ag, Al, and Cu, are proposed as an alternative to Au, and they can also provide plasmonic enhancement to ultrathin films. Furthermore, through an efficient way to optimize the structural dimensions of the nanoporous ultrathin film absorber, a trilayer system of TiO2/Ge/Au achieves the total solar absorptance over 89.3% with a wavelength range of 400–1100 nm.  相似文献   
3.
    
In this work, a tandem grating solar absorber is proposed, which can be easily fabricated on a wafer scale and is thermally stable up to 800 K. The base of the solar thermal absorber consists of a tungsten substrate, SiO2 spacer, and 2D tungsten nanohole array filled with SiO2. On top of the base structure, a 2D tungsten nanodisc array is coated with an additional SiO2 spacer, forming the tandem grating structure. The outside area of the nanodisc array is also filled with SiO2; thus, the proposed solar absorber is geometrically flat. In the solar spectrum from 0.3 to 2.0 μm, the total absorptance of the fabricated sample is measured to be 90%. On the other hand, in the mid‐infrared region from 3 to 15 μm, the total emittance is measured to be 23% at 800 K, which greatly suppresses the thermal emission loss. Finite‐difference time‐domain simulation suggests that the magnetic resonance and Rayleigh anomaly are responsible for the enhanced absorption of solar radiation. It is also shown that the spectral absorptance of the proposed solar absorber is nearly insensitive to the polarization angle as well as to the incidence angle in the spectrum of solar radiation.  相似文献   
4.
    
Absorbers for infrared light are important optical components in key areas like biosensing, infrared imaging, and (thermal) light emission, with special need for thin and reconfigurable devices. Here, the authors demonstrate ultra-thin, switchable infrared absorbers based on thin layers of chalcogenide phase-change materials (PCMs) with high optical contrast between a lossless amorphous and an exceptionally lossy crystalline phase (Ge3Sb2Te6, Ge2Sb2Te4, Ge2SbTe4, Ag4In3Sb67Te26, and GeTe) on top of polar substrates (SiC, Al2O3, and SiO2). It is found that light is mainly absorbed in the substrate for amorphous PCMs, and in the thin layer for crystalline PCMs. Using the concept of admittance matching, the authors demonstrate dramatic layer thickness reduction by a factor f = πκ of up to 14 for high PCM extinction coefficients κ compared to classic λ/4 anti-reflection coatings. The authors show continuous tuning of the maximum absorption wavelength by up to 2.5 µm in the epsilon-near-zero ranges of the substrates via annealing on a hot plate and optical switching. By selecting a suitable PCM-substrate combination, the tuning range and its size can be shifted through the whole infrared range. The results demonstrate that exceptionally lossy PCMs show great potential for ultra-thin, reconfigurable nanophotonic devices.  相似文献   
5.
A new fluorite-type solid solution domain has been evidenced in the system (1−x) CeO2x/7 Y6WO122 using the amorphous citrate route. All the studied phases (0?x?1) crystallize in a cubic-type symmetry. Diffuse reflectance spectra reveal a strong optical absorption between 380 and 400 nm. All substituted compositions spectral selectivities are estimated suitable for application as inorganic UV absorbers. The non linear variation observed in the optical gap values between Y6WO12 and CeO2 is attributed to the presence of the cerium 4f-block band. Additionally, Time Resolved Microwave Conductivity (TRMC) experiment and phenol photodegradation analyses carried out on the Ce0.81Y0.16W0.03O1.950.05 (x=0.19) composition do not indicate any photocalatytic activity for this material.  相似文献   
6.
K P J Reddy  P K Barhai 《Pramana》1990,35(6):527-532
Construction of a spatial light modulator (SLM) using reverse saturable absorber molecules is suggested. The SLM characteristics are derived using a recently proposed steady-state kinetic analysis. Results are presented for the rhodamine 6G dye molecules.  相似文献   
7.
柳强  巩马理等 《光学学报》2003,23(3):26-329
利用固体可饱和吸收体砷化镓(GaAs)作为被动调Q元件,实现了激光二极管抽运平-凹腔掺钕钒酸钇(Nd:YVO4)激光调Q运转,详细测量了砷化镓被动调QNd:YVO4激光输出特性,获得脉宽15ns,重复频率470kHz,光束质量M^2=1.31的激光输出,调Q激光运转阈值为500mW,并数值求解了砷化镓被动调Q速率方程,讨论了被动调Q机理以及调Q脉冲宽度和脉冲重复频率对抽运速率的依赖关系,理论计算结果与实验结果相一致。  相似文献   
8.
Nano-phased structures based on metal–dielectric composites, also called cermets (ceramic–metal), are considered among the most effective spectral selective solar absorbers. For high temperature applications (stable up to 650 °C) noble metal nanoparticles and refractory oxide host matrices are ideal as per their high temperature chemical inertness and stability: Pt/Al2O3 cermet nano-composites are a representative family. This contribution reports on the optical properties of Pt/Al2O3 cermet nano-composites deposited in a multilayered tandem structure. The radio-frequency sputtering optimized Pt/Al2O3 solar absorbers consist of stainless steel substrate/ Mo coating layer/ Pt–Al2O3/ protective Al2O3 layer and stainless steel substrate/ Mo coating layer /Pt–Al2O3 for different composition and thickness of the Pt–Al2O3 cermet coatings. The microstructure, morphology, theoretical modeling and optical properties of the coatings were analyzed by the x-ray diffraction, atomic force, microscopy, effective medium approximation and UV–vis specular and diffuse reflectance.  相似文献   
9.
Several approaches have been investigated to prepare fluorite-type compositions within the (1−x) CeO2-xYO1.5 system. The optical properties of the resulting modified-ceria materials have been characterized in order to evaluate their potential abilities as inorganic UV absorbers. Diffuse reflectance analyses reveal a strong optical absorption between 390 and 400 nm for all substituted compositions and the spectral selectivities are estimated suitable for the targeted application. Additionally, time resolved microwave conductivity (TRMC) and phenol photodegradation analyses do not indicate any photocalatytic activity for these compositions. Aqueous colloidal suspensions of the Ce0.7Y0.3O1.85 UV absorber have been carried out.  相似文献   
10.
    
A new systems theoretical approach to the design of passive vibration absorbers for elastic systems is presented. Undamped lumped parameter models of flexible mechanical structures are considered. Necessary and sufficient conditions are derived under which a preselected eigenfrequency spectrum can be assigned to such a system using an undamped lumped parameter vibration absorber. The realizable eigenfrequency spectra are analytically characterized, the required dynamical order of the absorber is established, and a design method for its parameters is outlined.  相似文献   
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