Tranzijentna apsorpcija Rodamina B

master's thesis

• Title (english): Transient Absorption of Rhodamine B
• Author: Vedran Brusar
• Mentor: Silvije Vdović (mentor)
• Mentor: Vedran Đerek (komentor)
• Committee member: Krešimir Kumerički (predsjednik povjerenstva)
• Committee member: Emil Tafra (član povjerenstva)
• Committee member: Vedran Đerek (član povjerenstva)
• Committee member: Silvije Vdović (član povjerenstva)
• Committee member: Ivica Smolić (član povjerenstva)
• Granter: University of Zagreb; Faculty of Science; (Department of Physics); Zagreb
• Defense date and country: 2020-09-24, Croatia
• Scientific / art field, discipline and subdiscipline: NATURAL SCIENCES; Physics

Abstract

Glavni cilj rada sastojao se u optimizaciji svih eksperimentalnih parametara kako bi se kroz mjerenja fotofizičkih svojstava molekula organske boje Rodamina B odredila maksimalna vremenska rezolucija eksperimentalnog postava za ultrabrzu tranzijentnu apsorpciju. Za pobudu sustava korišteni su ultrakratki laserski pulsevi stvoreni u nekolinearnom optičkom parametarskom pojačalu kućne izrade. Tranzijentno stanje se dobilo pobudivanjem molekula pomoću pumpnog pulsa valne duljine od 550 nm, dok je za probni puls, koji ispituje tranzijentno stanje, korišten superkontinuum bijele svjetlosti dobiven u pločici kalcijevog fluorida. Iz prilagodbi kinetičkih profila, tj. tranzijenata, za pojedine valne duljine od interesa na odgovarajuće modele dobiveni su parametri koji određuju vremensku rezoluciju eksperimentalnog postava što omogućuje indirektnu procjenu vremenskog trajanja pulseva koji nastaju u nekolinearnom optičkom parametarskom pojačalu. Iz mjerenja tranzijentne apsorpcije određene su vremenske rezolucije za različite postave eksperimenta, a dobivene vrijednosti kreću se u rasponu od 45 fs do 212 fs. Zaključeno je da na određivanje vremenske rezolucije utječu koherentni artefakti, prvenstveno medufazna modulacija. Ti artefakti su izraženiji za mjerenja s kraćim pulsevima pumpne zrake. Vrijeme trajanje pumpnog pulsa dodatno je provjereno mjerenjem spektralno razlučive autokorelacije pobudnog pulsa što je standardna metoda za karakterizaciju ultrabrzih (femtosekundnih) laserskih pulseva.

Abstract (english)

The main goal of the thesis was to optimize all experimental parameters in order to determine the maximum time resolution of the experimental setup for ultrafast transient absorption through measurements of photophysical properties of Rhodamine B organic dye molecules. The transient state was obtained by excitation of the molecules using a pump pulse with a wavelength of 550 nm, while for the probe pulse, which examines the transient state, a white light supercontinuum obtained in a calcium fluoride plate was used. From the fitting of the kinetic profiles, ie transients, for individual wavelengths of interest to the corresponding models, parameters were obtained that determine the time resolution of the experimental setup, which allows indirect estimation of the time duration of pulses generated in noncollinear optical parameter amplifier. From the transient absorption measurements, time resolutions were determined for different experimental setups, and the values obtained ranged from 45 fs to 212 fs. It was concluded that the determination of time resolution is influenced by coherent artifacts, primarily cross-phase modulation. These artifacts are more pronounced for measurements with shorter pump beam pulses. The duration of the pump pulse was additionally checked by measuring the spectrally resolved autocorrelation of the excitation pulse, which is the standard method for the characterization of ultrafast (femtosecond) laser pulses.

• Keywords: nelinearna optička interakcija; ultrabrza tranzijentna apsorpcija; femtosekundni pulsevi; nekolinearno optičko parametarsko pojačalo; superkontinuum bijele svjetlosti
• Keywords (english): nonlinear optical interaction; ultrafast transient absorption; femtosecond pulses; noncollinear optical parametric amplifier; white light supercontinuum
• Language: croatian
• URN:NBN: urn:nbn:hr:217:992421
• Study programme: Title: Physics; specializations in: Research; Course: Research; Study programme type: university; Study level: integrated undergraduate and graduate; Academic / professional title: magistar/magistra fizike (magistar/magistra fizike)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2021-01-19 09:41:55