High resolution imaging with differential infrared absorption micro-spectroscopy

• Published in: Optics express 2013-11, Vol.21 (22), p.25632-25642
• Main Authors: Pita, Isabel, Hendaoui, Nordine, Liu, Ning, Kumbham, Mahendar, Tofail, Syed A M, Peremans, André, Silien, Christophe
• Format: Article
• Language: English
• ISSN: 1094-4087; 1094-4087
• DOI: 10.1364/OE.21.025632

Although confocal infrared (IR) absorption micro-spectroscopy is well established for far-field chemical imaging, its scope remains restricted since diffraction limits the spatial resolution to values a little above half the radiation wavelength. Yet, the successful implementations of below-the-diffraction limit far-field fluorescence microscopies using saturated irradiation patterns for example for stimulated-emission depletion and saturated structured-illumination suggest the possibility of using a similar optical patterning strategy for infrared absorption mapping at high resolution. Simulations are used to show that the simple mapping of the difference in transmitted/reflected IR energy between a saturated vortex-shaped beam and a Gaussian reference with a confocal microscope affords the generation of high-resolution vibrational absorption images. On the basis of experimentally relevant parameters, the simulations of the differential absorption scheme reveal a spatial resolution better than a tenth of the wavelength for incident energies about a decade above the saturation threshold. The saturated structured illumination concepts are thus expected to be compatible with the establishment of point-like point-spread functions for measuring the absorbance of samples with a scanning confocal microscope recording the differential transmission/reflection.