Abstract

Quantitative phase imaging (QPI) techniques measures the phase shift by a specimen, enabling non-destructive applications in materials and life sciences. As a label-free modality, QPI is not restricted by phototoxicity or photobleaching. However, these attractive features come with the lack of chemical specificity. To fulfill this gap, we developed a bond-selective phase imaging (BPI) microscope that utilizes mid-infrared laser pulses to induce a local temperature rise via vibrational absorption, resulting in a transient phase change. This phase change is directly related to the spectroscopy of the specimen and is detected by a high-temporal-resolution QPI setup using a pulsed probe laser, adding dynamics information of the absorption and heat decay. We report high spectral fidelity, sub-microsecond temporal resolution BPI at 50 frames/sec. The setup is shown in Figure 1. Major results are shown in Figure 2. Our approach links the missing chemical information to the quantitative phase, which paves a new avenue for microscopic studies in biology and materials science.

© 2019 SPIE/OSA