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51.
Ryan P. Smith Peter A. Roos Jared K. Wahlstrand Jessica A. Pipis Maria Belmonte Rivas Steven T. Cundiff 《Journal of research of the National Institute of Standards and Technology》2007,112(6):289-296
We perform optical frequency metrology of an iodine-stabilized He-Ne laser using a mode-locked Ti:sapphire laser frequency comb that is stabilized using quantum interference of photocurrents in a semiconductor. Using this technique, we demonstrate carrier-envelope offset frequency fluctuations of less than 5 mHz using a 1 s gate time. With the resulting stable frequency comb, we measure the optical frequency of the iodine transition [127I2 R(127) 11-5 i component] to be 473 612 214 712.96 ± 0.66 kHz, well within the uncertainty of the CIPM recommended value. The stability of the quantum interference technique is high enough such that it does not limit the measurements. 相似文献
52.
Rare earth oxides/hydroxides are important emerging materials owing to their unique properties. Shape-controlled synthesis of elongated hexagonal bipyramid shaped La(OH)3 nanorods with different aspect ratios and trigram-shaped LaCO3OH nanosheets was systematically carried out by controlling the reaction conditions. Hydrazine and polyvinylpyrrolidone (PVP) surfactants used in synthesis are assumed to play a key “dual-template” role in determining the aspect ratio and shape of the resulting nanostructures. Elongated hexagonal bipyramid shaped La(OH)3 nanorods were found to grow along the preferred orientation [0001]. Six equivalent crystallographic facets, \((20\bar 20)\), \((02\bar 20)\), \((2\bar 200)\), \((0\bar 220)\), \((\bar 2200)\), and \((\bar 2020)\) lattice planes, were found to be exposed on the side surfaces on each nanorod as confirmed by combined transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and selected area electron diffraction (SAED) analyses. A double-polarization phenomenon was found to occur at the nanorod surfaces by employing off-axis electron holography, implying that the material could be used as an effective dielectric microwave absorber. La(OH)3 nanorods with larger aspect ratios exhibit better absorption properties with respect to the maximum reflection loss and effective absorbing bandwidth. Thus, a novel method towards the reasonable design of bipyramid shaped La(OH)3 nanorods exhibiting tunable microwave absorption properties is proposed based on our synthesis strategy. 相似文献
53.
Rahul G. Waghmare R.K. Sai Subrahmanyam Gorthi Deepak Mishra 《Journal of Modern Optics》2013,60(14):1384-1390
We propose a wrapped statistics-based approach for phase estimation from noisy reconstructed interference fringes in digital holographic interferometry. The state space model required here is formed by Taylor series expansion of the phase function as state model and the wrapped dynamical system as measurement model. Prediction of the state using Kalman filter is straightforward since the state model is linear. However, the non-linearity issue induced due to the wrapping of the measurements is handled by changing the innovation correction step, which accounts for the probability of wrappings. Through the simulation and experimental study, we have shown that the proposed approach is robust to both, noise in fringe pattern as well as the dynamic range of the phase pattern, simultaneously. Moreover, it outperforms when compared with the other state-of-the-art phase retrieval approaches. 相似文献
54.
55.
采用非临界相匹配方式,制成一台同步泵浦飞秒红外光参量振荡器。其输出波长的调谐是靠改变泵浦光掺钛蓝宝石激光器的输出波长而得以实现的,其调谐范围为1.08~1.13um。在90fs.1.1w左右的掺钛蓝宝石激光器的泵浦下,同步泵浦光参量振荡器的输出功率为100mw.而脉竟只有60fs左右。 相似文献
56.
57.
Bingrui Liu Bin Dong Chen Xin Chao Chen Leran Zhang Dawei Wang Yanlei Hu Jiawen Li Li Zhang Dong Wu Jiaru Chu 《Small (Weinheim an der Bergstrasse, Germany)》2023,19(2):2204630
Biomimetic stimuli-responsive structure colors (SCs) can improve the visualization and identification in the micro functional structure field such as information encryption/decryption and smart actuators. However, it is still challenging to develop the ability to 4D print arbitrary submerged colorful patterns with stimuli-responsive materials at the microscale. Herein, a hydrogel photoresist with feature resolution (98 nm) for the fabrication of 4D microscopic SCs by the femtosecond direct laser writing method is developed. The 4D printed woodpile SCs are grouped as pixel palettes with various laser parameters and they spanned almost the entire color space. The coloring mechanism of diffraction gratings is not only investigated by optics microscopy and spectroscopy but also supported by simulation. Moreover, the 4D printed hydrogel-integrated amphichromatic fish constructions and pixelated painting can visually discolor reversibly by regulating the solution pH. This finding promises an ideal coloring method for sensors, anti-counterfeiting labels, and transformable photonic devices. 相似文献
58.
Fang Liang Jorge Lehr Lisa Danielczak Richard Leask Anne-Marie Kietzig 《International journal of molecular sciences》2014,15(8):13681-13696
Nature shows many examples of surfaces with extraordinary wettability, which can often be associated with particular air-trapping surface patterns. Here, robust non-wetting surfaces have been created by femtosecond laser ablation of polytetrafluoroethylene (PTFE). The laser-created surface structure resembles a forest of entangled fibers, which support structural superhydrophobicity even when the surface chemistry is changed by gold coating. SEM analysis showed that the degree of entanglement of hairs and the depth of the forest pattern correlates positively with accumulated laser fluence and can thus be influenced by altering various laser process parameters. The resulting fibrous surfaces exhibit a tremendous decrease in wettability compared to smooth PTFE surfaces; droplets impacting the virgin or gold coated PTFE forest do not wet the surface but bounce off. Exploratory bioadhesion experiments showed that the surfaces are truly air-trapping and do not support cell adhesion. Therewith, the created surfaces successfully mimic biological surfaces such as insect wings with robust anti-wetting behavior and potential for antiadhesive applications. In addition, the fabrication can be carried out in one process step, and our results clearly show the insensitivity of the resulting non-wetting behavior to variations in the process parameters, both of which make it a strong candidate for industrial applications. 相似文献
59.
论述了对于用声全息反演法测量水声材料任意入射角的反射系数,用柱面波分解比平面波分解优越的理由,平面波分解计算采用快速傅立叶变换受到波数域的分辨率及声波波长的限制,不能测量到任意入射角的反射系数;而柱面波分解理论则无上述限制,能测量任意入射角的反射系数,柱面波分解法利用了声源及测试材料声反射面的轴对称性,只需测量半径方向上的复声压数据,极大地减少了工作量。随后以水中8毫米厚的铝板为例,通过数值模拟,分析了测量过程中各种因素对测量精度的影响,这些因素包括测量半径、阵元及阵位置误差、阵元间隔、测量面高度的定位误差等,指出了实际测量过程中对这些因素均有很高的要求,低频条件下声源若不满足指向性很高的要求,测量大入射角的反射系数仍然存在困难。 相似文献
60.
Tomoyoshi Shimobaba Takashi Kakue Nobuyuki Masuda Tomoyoshi Ito 《Journal of the Society for Information Display》2012,20(9):533-538
Holographic projection is for laser displays and has the merits of being aberration free, producing high‐contrast images, having the ability of color reconstruction with one spatial light modulator, and so on. In this paper, we propose a zoomable holographic projection without using a zoom lens and verify the proposed method by using numerical simulation. Although such a system can be readily realized to use the features of holography, which is capable of recording a large image exceeding the hologram size, the required calculation is very time consuming. For acceleration, we used shifted Fresnel diffraction for setting different sampling rates on a hologram and projected image. The proposed method can project any zoom‐in and zoom‐out image between zeroth‐order and first‐order lights, and the processing time and required memory for the zoom are constant. 相似文献