NASA和麻省理工学院合作开发天基量子点光谱仪

2017-02-15 13:19:24 来源: 中国科技网 作者: 张微编译

美国宇航局的技术专家与一项新的纳米技术的发明者进行了合作研究,该技术能够转变太空科学家建造光谱仪的方式,光谱仪是所有科学领域用来测量光(天体发出的,包括地球的)的特性的最重要装置。

Mahmooda Sultana,是NASA哥达德太空飞行中心(位于马里兰州格林贝尔特)的工程师,他正在与麻省理工学院的化学教授Moungi Bawendi合作,开发一个基于新兴量子点技术(Bawendi团队开发)的成像光谱仪原型机。

美国宇航局的中心创新基金为这项具有开创性的、高风险技术提供了资金支持。

量子点是上世界80年代早期发现的一种半导体纳米晶体。肉眼不可见,根据它们的尺寸、性质和化学成分,量子点可以吸收不同波长的光。该技术有望应用于依赖光分析的领域,包括智能手机摄像头,医疗设备和环境测试设备。

“这是该技术领域的新发现,” Sultana说,所指的是,她认为能够让天基光谱仪小型化和革命化的技术,尤其是那些应用于无人飞行器和小型卫星上的光谱仪。“它确实可以简化仪器的集成。”

吸收光谱仪,顾名思义,根据它们吸收的光的频率或波长可以测量光的吸收,因为它们能够与样本相互作用,如大气气体。

穿透样本或与样本相互作用之后,光线到达光谱仪。传统的光谱仪利用光栅、棱镜或干涉滤光片将光分解成其组成成分的波长(它们的探测器像素),然后探测产生光谱。光谱吸收的越强,特定化学物质存在的就越多。

由于设备小型化,天基光谱仪越来越小型化,但是它们的尺寸仍然较大,Sultana说。“高光谱分辨率对于利用光栅和棱镜的设备来说需要长的光路。这就导致的设备体积大。而量子点就像过滤器一样,根据它们的尺寸和形状吸收不同波长,我们可以建造一个体积小的设备。换句话说,你可以不用光学零件,如光栅、棱镜、干涉滤光片。”

同样重要的是,该技术能够让仪器开发人员产生几乎无限数量的不同量子点。当它们的尺寸减小时,量子点吸收的光的波长也将减少。“这样就可以产生一个持续可调的,独立的一组吸收滤波器,其中每个像素都是由特定尺寸、形状或成分的量子点组成。我们可以精确控制每个量子点的吸收。我们就能够定制仪器,用高光谱分辨率来观察不同波段。”

有了NASA的技术支持,通过热真空和振动试验,Sultana正在开发论证一个对可见光(太阳和极光成像必需的)敏感的20-by-20量子点阵列。该技术可以扩展到更广的波长范围,从紫外光到中红外光,这些光线在地球科学、太阳物理学和行星科学等许多空间应用中都可以找到,她说。

通过协作,Sultana正在为立方体卫星应用开发一个概念仪器,麻省理工学院的博士生Jason Yoo正在研究一项技术,合成不同易制毒化学品来创建量子点,然后将它们打印到合适的承印物上。“最后,我们想要将量子点直接打印到探测器像素上,”她说。

“这是一项非常新颖的技术,” Sultana补充道,不过她也承认现在还处于开发的早期阶段。“但是,我们正在努力,快速地提高技术水平。将会有几个太空科学任务从这项技术中受益。”(张微编译)

以下为英文原文:

NASA and MIT Collaborate to develop space-based quantum-dot spectrometer

A NASA technologist has teamed with the inventor of a new nanotechnology that could transform the way space scientists build spectrometers, the all-important device used by virtually all scientific disciplines to measure the properties of light emanating from astronomical objects, including Earth itself.

Mahmooda Sultana, a research engineer at NASA's Goddard Space Flight Center in Greenbelt, Maryland, now is collaborating with Moungi Bawendi, a chemistry professor at the Cambridge-based Massachusetts Institute of Technology, or MIT, to develop a prototype imaging spectrometer based on the emerging quantum-dot technology that Bawendi's group pioneered.

NASA's Center Innovation Fund, which supports potentially trailblazing, high-risk technologies, is funding the effort.

Quantum dots are a type of semiconductor nanocrystal discovered in the early 1980s. Invisible to the naked eye, the dots have proven in testing to absorb different wavelengths of light depending on their size, shape, and chemical composition. The technology is promising to applications that rely on the analysis of light, including smartphone cameras, medical devices, and environmental-testing equipment.

"This is as novel as it gets," Sultana said, referring to the technology that she believes could miniaturize and potentially revolutionize space-based spectrometers, particularly those used on uninhabited aerial vehicles and small satellites. "It really could simplify instrument integration."

Absorption spectrometers, as their name implies, measure the absorption of light as a function of frequency or wavelength due to its interaction with a sample, such as atmospheric gases.

After passing through or interacting with the sample, the light reaches the spectrometer. Traditional spectrometers use gratings, prisms, or interference filters to split the light into its component wavelengths, which their detector pixels then detect to produce spectra. The more intense the absorption in the spectra, the greater the presence of a specific chemical.

While space-based spectrometers are getting smaller due to miniaturization, they still are relatively large, Sultana said. "Higher-spectral resolution requires long optical paths for instruments that use gratings and prisms. This often results in large instruments. Whereas here, with quantum dots that act like filters that absorb different wavelengths depending on their size and shape, we can make an ultra-compact instrument. In other words, you could eliminate optical parts, like gratings, prisms, and interference filters."

Just as important, the technology allows the instrument developer to generate nearly an unlimited number of different dots. As their size decreases, the wavelength of the light that the quantum dots will absorb decreases. "This makes it possible to produce a continuously tunable, yet distinct, set of absorptive filters where each pixel is made of a quantum dot of a specific size, shape, or composition. We would have precise control over what each dot absorbs. We could literally customize the instrument to observe many different bands with high-spectral resolution."

With her NASA technology-development support, Sultana is working to develop, qualify through thermal vacuum and vibration tests, and demonstrate a 20-by-20 quantum-dot array sensitive to visible wavelengths needed to image the sun and the aurora. However, the technology easily can be expanded to cover a broader range of wavelengths, from ultraviolet to mid-infrared, which may find many potential space applications in Earth science, heliophysics, and planetary science, she said.

Under the collaboration, Sultana is developing an instrument concept particularly for a CubeSat application and MIT doctoral student Jason Yoo is investigating techniques for synthesizing different precursor chemicals to create the dots and then printing them onto a suitable substrate. "Ultimately, we would want to print the dots directly onto the detector pixels," she said.

"This is a very innovative technology," Sultana added, conceding that it is very early in its development. "But we're trying to raise its technology-readiness level very quickly. Several space-science opportunities that could benefit are in the pipeline."

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