An approach to breaking through the diffraction limitation in infrared microscopies is put forward in this paper. In this method, instead of Gaussian pump beam, an intensive vortex beam is first focused on the sample, leading to the saturation absorption of peripheral molecules in the point spread function (PSF). The vortex beam is followed by a Gaussian probe beam with the same wavelength. Because of the previous saturation absorption, the probe beam can only be absorbed by the molecules near the center, resulting in a shrunk PSF which means super-resolution. Furthermore, the PSF of a system based on this approach is numerically simulated. With a 100 nJ pulse energy vortex beam and a 0.1 nJ pulse energy probe beam, the theoretical resolution FWHM (full width at half maximum) is measured to be about 236 nm which is 14 times better than that of the traditional infrared microscopy.%本文提出一种突破衍射极限的红外显微成像方法,该方法基于抽运-探测模式,采用了环形而非高斯型强度分布的抽运光,由于样品在环形光强度峰值附近区域达到吸收饱和,因此当高斯分布的探测光随后到达样品时,只有环形光的中心区域才能吸收探测光的能量,而且吸收区域随着环形光的强度增加而减小.这意味着,如果以被吸收的探测光能量作为该成像系统的信号,本文提出的方法可以使系统的分辨率超越衍射极限的限制.本文模拟了不同环形光能量下成像系统的空间分辨率,结果表明：当环形光能量为100 nJ、探测光能量为0.1 nJ时,该方法的理论分辨率在236 nm,比传统红外显微成像系统分辨率提高了约14倍.
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