Experimental Principle of Passive Near-Field Infrared Microscope
Infrared thermal imaging technology detects the far-field infrared radiation emitted by an object itself to sense surface temperature, and has wide applications in important fields such as military, civil aviation, security monitoring, and industrial manufacturing. However, due to the limitation of optical diffraction limits, the resolution of infrared thermal imaging is usually at the micrometer scale or above, and therefore cannot be used to observe objects at the nanometer scale. In recent years, we have developed infrared passive near-field microscopy imaging technology, which greatly breaks through the limit of infrared diffraction by detecting the near-field radiation on the surface of objects, and expands infrared temperature detection and imaging from the traditional micrometer scale to the nanometer scale.
According to Myers Consulting, recently, the scientific research team of the National Key Laboratory of Infrared Science and Technology of the Chinese Academy of Sciences Shanghai Institute of Technical Physics published an article on the theme of "infrared near-field radiation detection and super-resolution temperature imaging" in the Journal of Infrared and Millimeter Wave. The first author of this article is Zhu Xiaoyan, mainly engaged in research on infrared passive near-field imaging.
This article will focus on the experimental principle and application of Scanning Noise Microscopy (SNoiM) technology, and provide a detailed introduction on how to break through the diffraction limit of infrared thermal imaging and achieve nanoscale infrared temperature imaging through the independently developed infrared passive near-field microscope.
near-field radiation
We first start with the origin of blackbody radiation. As shown in Figure 1 (a), the vast majority of objects contain a large number of positively and negatively charged particles inside, which never come to a standstill but remain in a state of random disturbance (thermal motion). The well-known thermal radiation originates from the thermal motion of charged particles inside an object, and the radiation characteristics can be described by Planck's blackbody radiation law. However, little known is that charge disturbances within an object not only generate infrared thermal radiation (far-field radiation) in areas beyond the wavelength scale of the object's radiation, but also generate a highly energy dense surface disturbance electromagnetic wave (in the form of evanescent waves) near the object's surface, which can be referred to as near-field radiation. Theory has long predicted the existence of surface electromagnetic waves (near-field radiation) and found that the knowledge and laws established for far-field radiation (such as Planck's radiation law) will no longer apply to near-field radiation. However, related experimental research has not made significant breakthroughs due to the extremely high difficulty of detection. In 2009, research teams from the Massachusetts Institute of Technology (MIT) in the United States and CNRS in France made significant progress by experimentally verifying that the near-field radiative heat transfer efficiency at the nanoscale can far exceed the blackbody radiation limit. Although the experiment confirmed the existence of near-field evanescent waves on the surface of objects, there is still a lack of more direct experimental methods to further study the related physical phenomena.
