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High resolution reflection microscopy via absorbance modulation

High resolution reflection microscopy via absorbance modulation

Session

Stream 6 (Frontiers): Development and Applications in Super Resolution Microscopy

Authors

Parul Jain (2), Viktor Udachin (1), Sven Nagorny (3), Dr. Claudia Geisler (2), Apl. Prof. Dr. Jörg Adams (4), Prof. Dr. Andreas Schmidt (3), Prof. Dr. Christian Rembe (5), Apl. Prof. Dr. Alexander Egner (2)

Affiliations

1. Clausthal Center of Materials Technology, TU Clausthal
2. Institut für Nanophotonik
3. Institut für Organische Chemie,TU Clausthal
4. Institut für Physikalische Chemie, TU Clausthal
5. Institute of Electrical Information Technology, TU Clausthal

Keywords

Reflection microscopy, Absorbance modulation

Abstract text

Properties of composite materials are strongly influenced by their microstructural features. The size of these features can vary from a few nanometers to several micrometers. Optical microscopy, especially reflection microscopy, is one of the primary tools for the morphological characterization in material science. However, due to the wave nature of light, it cannot be focused to an arbitrarily small spot, thereby limiting the resolution of optical microscopes to the diffraction limit that is not sufficient for the analysis of these materials. Stimulated emission depletion (STED) microscopy, which is so far mostly used in life science imaging, surpasses the diffraction limit by exploiting the properties of fluorescent markers [1]. The concept of STED has been successfully applied in optical lithography and microscopy as a technique called absorbance-modulation [2]. In absorbance modulation, a layer of photochromic molecules, referred to as absorbance modulation layer (AML), is coated on the sample that can change their absorption properties when illuminated with light of different wavelengths. Thus, they can be reversibly switched between opaque and transparent configuration in a controlled manner and consequently, increase the resolution. This technique of absorbance modulation when applied for imaging is called absorbance modulation imaging (AMI). AMI in transmission microscopy has certainly demonstrated a high lateral resolution [3]. However, AMI in reflection microscopy has not yet been demonstrated, despite its potential to analyze a much wider range of materials including opaque, transparent, and even metallic samples.

Theoretical study on AMI in confocal reflection microscopy predicts that imaging beyond the diffraction limit is indeed possible [4]. Here we experimentally validate this prediction by demonstrating one-dimensional AMI. When a one-dimensional grating sample, coated with a thin layer of AML, is illuminated with a Gaussian-shaped focus superposed with a 1-D pattern (similar to transverse laser mode 01), a dynamic aperture is generated within the AML. The size of this effective aperture is below the diffraction limit which allows to achieve sub-wavelength resolution. Further resolution improvement is possible by optimizing the illumination scheme and tailoring the optical absorption response of the AML. The one-dimensional AMI that we demonstrate here can be easily extended to two dimensions which would facilitate high resolution optical imaging of microstructural features.

References

[1] S. W. Hell, J. Wichmann, Opt. Letters, Vol. 19, No. 11 (1994).

[2] R. Menon, H. I. Smith, J. Opt. Soc. Am., A 23, 2290 (2006).

[3] H.Y. Tsai, S. W. Thomas, III, R. Menon, Opt. Express, Vol.18, No. 15 (2010).

[4] R. Kowarsch, C. Geisler, A. Egner, C. Rembe, Opt. Express, 26(5), p. 5327–5341 (2018).