Development of a multimodal nonlinear imaging system for biophotonic applications

Dwapanyin, George Okyere (2020-04)

Thesis (PhD)--Stellenbosch University, 2020.

Thesis

ENGLISH ABSTRACT: Multiphoton microscopy techniques have gained wide prominence in biophotonics imaging applications since their inventions. Compared to conventional optical imaging, these nonlinear optical microscopy (NLOM) techniques are intrinsically confocal, and thus enables three-dimensional imaging with submicron spatial resolution. Additional advantages include decreased photodamage to tissue, increased depth of penetration as well as the ability to perform label-free imaging. Signal response in NLOM techniques depend nonlinearly on the peak intensity, therefore requiring a high peak intensity laser as source. Control of ultrashort pulses enables the generation of high peak intensity pulses with lower excitation pulse energies. This dissertation focuses on the development of a nonlinear microscopy system for biological applications based on the control of the spectral phase of broadband supercontinuum pulses generated in a polarization maintaining all normal dispersion photonic crystal fibre. We further demonstrate, for the first time, the real world application of a time domain ptychographic phase measurement technique known as i2PIE which allows for phase correction at the object plane, in microscopy, and how this phase control contributes to image enhancement in two photon excitation fluorescence (TPEF) and second harmonic generation (SHG) imaging of biological tissue. By comparing this new technique to the commonly used multiphoton intrapulse interference phase scan (MIIPS) measurement technique, we show that i2PIE offers an improved spectral phase measurement which can be used to generate shorter temporal pulses and ultimately produce higher peak intensities, even at lower pulse energies. Our results also show that for the same input pulse energies, i2PIE provides a higher contrast image and an improved signal to noise ratio compared to MIIPS. The results obtained from this work projects i2PIE as a promising phase measurement technique for the coherent control of ultrashort pulses used in nonlinear microscopy.

AFRIKAANSE OPSOMMING: Multi-foton mikroskopie tegnieke het wye aanklank in biofotonika afbeelding toepassings gevind sedert hulle ontwikkeling. Vergeleke met konvensionele optiese afbeelding, is hierdie nielineêre optiese mikroskopie (NLOM) tegnieke intrinsiek konfokaal, en dus laat dit drie dimensionele afbeelding met ’n sub-mikron ruimtelike resolusie toe. Verdere voordele sluit in ’n afname in lig-skade aan weefsel, dieper penetrasie en die moontlikheid om merker vrye afbeelding uit te voer. Die sein sterkte in NLOM tegniekehangnielineêrafvandiepiekintensiteit, engevolglikbenodigdit’nhoëpiek intensiteit laser as bron. Beheer oor ultra-kort pulse laat die vorming van hoë intensiteit pulse met laer opwekkings puls energieë toe. Hierdie proefskrif fokus op die ontwikkelingvan’nnielineêremikroskopiesisteemvirbiologiesetoepassingsgebaseer op die beheer van die spektrale fase van breëband super-kontinuum pulse gegenereer in ’n volkome-normale-dispersie-fotoniese-kristal-vesel wat polarisasie behou. Ons demonstreer verder, vir die eerste keer, die werklike toepassing van ’n tyd-gebiedstigografie fase meet tegniek genaamd i2PIE, wat dit moontlik maak om die fase te korrigeer by die objek vlak in ’n mikroskoop, asook hoe hierdie fase beheer bydrae tot ’n verbetering van die gevormde beeld tydens twee-foton-opwekkings fluoressensie en tweede harmoniek opwekking afbeelding van biologiese weefsel. Deur hierdie tegnieke te vergelyk moet die algemeen gebruikte multi-foton intra-puls interferensie fase skandering (MIIPS) meet tegniek, wys ons dat die i2PIE ’n verbeterde spektrale fase meeting lewer wat gebruik kan word om korter pulse te genereer en gevolglik hoër piek intensiteite, selfs by laer pulse energieë. Ons resultate wys ook dat vir dieselfde inset puls energieë lewer i2PIE ’n hoër kontras beeld en ’n verbeterde sein tot geraas verhouding as MIIPS. Die resultate verkry uit hierdie werk toon i2PIE as ’n belowende fase meet tegniek vir die koherente beheer van ultra-kort pulse wat in nielineêre mikroskopie gebruik word.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/107913
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