Coherent non-linear microscopy employing novel femtosecond laser sources

Gudavicius, Dominykas 2024. Coherent non-linear microscopy employing novel femtosecond laser sources. PhD Thesis, Cardiff University. Item availability restricted.

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Abstract

Coherent Raman scattering (CRS) which is divided into Coherent anti-Stokes Raman scattering (CARS) and stimulated Raman scattering (SRS) microscopy combined with second/third harmonic generation (SHG/THG) is powerful label-free imaging method which is demonstrated in this thesis with various experimental setups. It provides concise history and introduction to CRS/SHG/THG microscopy and molecule vibrations. It further dives into background of the instrumentation used throughout the thesis such as pulsed lasers, optical parametric devices and how they are used in microscopy. Pulse characterization methods are described which allow to control pulse duration for most optimal spectral resolution in CARS/SRS experiments when femtosecond pulses are used. Following that, the thesis introduces basics of noise theory that provides noise characterization of commercially available OPO. Two laser systems with different gain material are compared (Yb and Ti:Sa) and it is concluded that both are shot-noise limited and suitable for SRS microscopy. To demonstrate SRS, Calu-3 cells were images by both systems. Later, microscopy layout changes are explained which allowed to add dual CARS modality to an existing setup. Experiments were performed which show that it is possible to record polystyrene (PS) and polymethyl methacrylate (PMMA) bead flow without motion artifacts and to simultaneously record deuterated water and water inside HeLa cells by using commercially available OPO. Additionally, it includes technique to perform pre-resonance SRS. Finally, novel technique which uses amplified laser system and multiple focal points to image the sample are introduced and discussed in detail. The image reconstruction and optimization algorithms of multifocal approach allow to reconstruct an image with PSF size similar to previously reported in confocal microscopy.

Item Type:	Thesis (PhD)
Date Type:	Completion
Status:	Unpublished
Schools:	Physics and Astronomy
Subjects:	Q Science > QC Physics
Uncontrolled Keywords:	Non-linear microscopy, wide-field microscopy, coherent Raman scattering, CRS, coherent anti-Stokes Raman scattering, CARS, stimulated Raman scattering, SRS, mode locking, lasers, optical parametric amplifiers, OPA, optical parametric oscillators, OPO
Funders:	Self funded
Date of First Compliant Deposit:	17 September 2024
Last Modified:	17 Sep 2024 11:13
URI:	https://orca.cardiff.ac.uk/id/eprint/172164

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