Chemical imaging with high spatial resolution and spectroscopic information opens a new window in understanding molecular behavior in a complex system such as a live cell. Vibrational spectroscopic imaging based on infrared (IR) absorption offers a way for mapping specific chemical bonds. However, direct IR imaging suffers from poor spatial resolution due to long excitation wavelength and strong water absorption. Detecting the thermal-induced refractive index change with a visible beam offers an effective way of beating the limitation in spatial resolution. We present a superfast chemical imaging platform that detects the mid-infrared photothermal effect using a wide-field IR illumination and visible beam detection scheme (Figure 1). Bond-selective contrasts are created by comparing the reflection images with and without pulsed IR light on the sample. Performance of the system is characterized by investigating the thermal relaxation time, pulse width, and delay between two beams. Superfast vibrational imaging of biological samples at speed of 100 frames per second will be demonstrated.

Sub-micron resolution chemical imaging by wide-field mid-infrared photothermal microscopy

256th National Meeting (2018)

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