6月28日Nature封面故事：频率可调的纳米线光源
生物谷报道：纳米光子学（研究光在纳米尺度上的性质的一个学科）有可能使电信、计算和传感等领域发生革命性变化。发表在6月28日Nature的封面文章介绍的一种新开发的频率可调的纳米线光源，可能会对纳米光子学的发展做出贡献，尤其是生物成像应用方面，因为它能在生理条件下发挥功能，确保对样本的损伤最小。 文章的标题是：“可调式纳米非线性光学探测器。这篇文章的其它合著者分别为：尤里.纳卡亚玛、彼得.鲍左斯基、亚历山德拉.拉德诺维克、罗伯特.奥诺拉托和理查德.塞卡里。
来自美国能源部劳伦斯·伯克利国家实验室和加州大学伯克利分校的研究小组开发出一种能够在可见光谱范围内发出相干光的生物友好型纳米级光源。一旦该技术得到加强和改进，这种纳米级光源的应用前景将十分广阔，这些应用包括单细胞内窥镜检查、其它形式的“亚波长”生物成像技术、基于纳米光子技术的集成电路和先进的新型计算机加密法。
该光源由一种无机材料（铌酸钾）制成，该材料具有非线性光学性质（因而能将光从一个频率转换成另一个频率）。研究人员可以用光钳将这种光源稳稳夹住，然后在一个试样上扫描。这样获得的图像能够显示具有亚波长分辨率的简单结构。除了生物成像外，这种方法还可用在先进信息技术、密码学和信号处理电路中。
该项目的主要研究员之一，化学家杨培东说：“我们利用个体纳米线开发出了第一种无电极的，持续可调式相干光源，这种光源可以与生理环境相互兼容。”杨培东是纳米科学界的权威人士，他在伯克利国家实验室分子铸造分部、材料科学分部和加州大学伯克利分校化学系身兼数职。“我们的试验还表明，这种光源可以利用光学镊子诱捕并操纵单一纳米线，这种能力十分重要，它不仅可以应用于生物成像技术，还可以应用于纳米光子集成电路。”
生物物理学家简·里法茨是另一名主要的研究人员，他身兼伯克利国家实验室物理生物科学分部和加州大学伯克利分校物理系的两项任职。里法茨说：“有了这种纳米线光源好比有了一个微型手电筒，我们可以利用它来扫描整个活细胞，从而在与细胞进行机械式接合的同时用肉眼观察细胞。”
封面图片所示为，研究人员正在用一个束缚的纳米线在液体环境中扫描涂有颜料的微珠。
部分英文原文：
Nature 447, 1098-1101 (28 June 2007) | doi:10.1038/nature05921; Received 20 October 2006; Accepted 11 May 2007
Tunable nanowire nonlinear optical probe
Yuri Nakayama1,6,7, Peter J. Pauzauskie1,5,7, Aleksandra Radenovic2,4,7, Robert M. Onorato1,7, Richard J. Saykally1,4, Jan Liphardt2,3,4 & Peidong Yang1,5
- Department of Chemistry,
- Department of Physics, and,
- Biophysics Graduate Group, University of California
- Physical Biosciences Division and,
- Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
- Materials Laboratories, Sony Corporation, 4-16-1 Okata, Atsugi-shi, Kanagawa 243-0021, Japan
- These authors contributed equally to this work.
Correspondence to: Jan Liphardt2,3,4Peidong Yang1,5 Correspondence and requests for materials should be addressed to J.L. (Email: liphardt@physics.berkeley.edu) or P.Y. (Email: p_yang@berkeley.edu).
Abstract
One crucial challenge for subwavelength optics has been the development of a tunable source of coherent laser radiation for use in the physical, information and biological sciences that is stable at room temperature and physiological conditions. Current advanced near-field imaging techniques using fibre-optic scattering probes1, 2 have already achieved spatial resolution down to the 20-nm range. Recently reported far-field approaches for optical microscopy, including stimulated emission depletion3, structured illumination4, and photoactivated localization microscopy5, have enabled impressive, theoretically unlimited spatial resolution of fluorescent biomolecular complexes. Previous work with laser tweezers6, 7, 8 has suggested that optical traps could be used to create novel spatial probes and sensors. Inorganic nanowires have diameters substantially below the wavelength of visible light and have electronic and optical properties9, 10 that make them ideal for subwavelength laser and imaging technology. Here we report the development of an electrode-free, continuously tunable coherent visible light source compatible with physiological environments, from individual potassium niobate (KNbO3) nanowires. These wires exhibit efficient second harmonic generation, and act as frequency converters, allowing the local synthesis of a wide range of colours via sum and difference frequency generation. We use this tunable nanometric light source to implement a novel form of subwavelength microscopy, in which an infrared laser is used to optically trap and scan a nanowire over a sample, suggesting a wide range of potential applications in physics, chemistry, materials science and biology.
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