Lee Eun Seong, Lee Jae Yong
Division of Convergence Technology, Korea Research Institute of Standards and Science, Yuseong-Gu, Daejeon, South Korea.
Opt Express. 2011 Jan 17;19(2):1378-84. doi: 10.1364/OE.19.001378.
We developed a nonlinear optical infrared microscope exploiting a thermally induced refractive index change in the mid-infrared regime and imaged a single biological cell with high spatial resolution that was not possible in conventional infrared microscopes. A refractive index change of a sample induced by infrared (~3.5 μm) absorption was probed by a visible (633 nm) laser beam. Thus the chemical specificity stems from the spectral absorbance of specimen and the spatial resolution from the short wavelength visible radiation. A reflecting objective (NA0.5) was used to focus the infrared and visible beams on the sample plane, and the sample was raster-scanned for 2-D imaging. The high resolution beyond the infrared diffraction limit was demonstrated by imaging fine grating lines made up of epoxy grooves (830 lines/mm). The probe wavelength dependence of the spatial resolution was investigated by imaging polystyrene beads. We found that the resolution was as small as 0.7 μm with 633 nm probe wavelength.
我们开发了一种非线性光学红外显微镜，利用中红外波段热致折射率变化，以高空间分辨率对单个生物细胞成像，这在传统红外显微镜中是无法实现的。由红外（约3.5μm）吸收引起的样品折射率变化由可见（633nm）激光束探测。因此，化学特异性源于样品的光谱吸收率，而空间分辨率源于短波长可见光辐射。使用反射物镜（NA0.5）将红外和可见光束聚焦在样品平面上，并对样品进行光栅扫描以进行二维成像。通过对由环氧凹槽（830线/毫米）组成的精细光栅线成像，证明了超越红外衍射极限的高分辨率。通过对聚苯乙烯珠成像研究了空间分辨率的探测波长依赖性。我们发现，在633nm探测波长下，分辨率可低至0.7μm。
