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Proceedings Paper

Super-resolution imaging with mid-IR photothermal microscopy on the single particle level
Author(s): Zhongming Li; Masaru Kuno; Gregory Hartland
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Paper Abstract

Photothermal microscopy has achieved single molecule sensitivity. However, the analytes are usually restricted to be natural absorbers in the visible light region. Mid-infrared (MIR) imaging, on the other hand, provides a wealth of information, but encounters difficulties of diffraction-limited spatial resolution and scarcity of ideal detectors. Here we present Mid-IR photothermal heterodyne imaging (MIR-PHI) microscopy as a high sensitivity, super-resolution mid-IR imaging technique. In MIR-PHI, a tunable Mid- IR pulsed laser at 150 kHz is used to excite a micron sized particle. Energy relaxation creates a temperature gradient around the particle, changing the refractive index of the surrounding solvent and creating a thermal lens. A collinear, counter propagating probe beam (a 532 nm CW laser) is modified by the thermal lens and generates a super-resolution photothermal image. We studied 1.1 μm polystyrene beads at the single particle level using this technique. Various solvents with different heat capacities and refractive indices are tested for the best image contrast. The wide applicability and potentially high sensitivity of this technique make it promising for biological imaging and identification.

Paper Details

Date Published: 20 August 2015
PDF: 8 pages
Proc. SPIE 9549, Physical Chemistry of Interfaces and Nanomaterials XIV, 954912 (20 August 2015); doi: 10.1117/12.2188337
Show Author Affiliations
Zhongming Li, Univ. of Notre Dame (United States)
Masaru Kuno, Univ. of Notre Dame (United States)
Gregory Hartland, Univ. of Notre Dame (United States)

Published in SPIE Proceedings Vol. 9549:
Physical Chemistry of Interfaces and Nanomaterials XIV
Sophia C. Hayes; Eric R. Bittner, Editor(s)

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