Control of CO2 vibrational dynamics via shaped-pulse coherent anti-Stokes Raman spectroscopy
| dc.contributor.advisor | Hermann, Uys | en_ZA |
| dc.contributor.author | Attie, Hendriks | en_ZA |
| dc.contributor.other | Stellenbosch University. Faculty of Science. Dept. of Physics | en_ZA |
| dc.date.accessioned | 2017-02-06T11:23:40Z | |
| dc.date.accessioned | 2017-03-29T11:36:35Z | |
| dc.date.available | 2017-02-06T11:23:40Z | |
| dc.date.available | 2017-03-29T11:36:35Z | |
| dc.date.issued | 2017-03 | |
| dc.description | Thesis (PhD)--Stellenbosch University, 2017 | en_ZA |
| dc.description.abstract | ENGLISH ABSTRACT : In this work we investigate the coherent control of carbon dioxide (CO2) vibrational dynamics using Coherent anti-Stokes Raman Scattering (CARS). During CARS, vibrational modes are excited via stimulated Raman scattering (SRS). Subsequently a narrowband probe field interacts with the molecular ensemble providing not only information about the modes populated, but also on the evolution of the wave-packet created during excitation. By spectrally shaping one of the SRS pump fields the vibrational dynamics can be controlled. In this work it was assumed that the pump pulse structure which will lead to a desired dynamics is unknown. To find that structure, a learning algorithm was developed which utilizes a spatial light modulator (SLM) in a 4f-optical con guration to spectrally shape the pump. Both a time-frequency representation of the shaped pulse (called the von Neumann basis) and a standard Fourier domain representation were bench-marked during optimization of a second harmonic generation (SHG) signal in a BBO crystal to ascertain which will suit the optimization problem best in terms of convergence rate and parameter space size. It was found that the von Neumann basis converged faster than the standard Fourier domain representation while still operating on a larger parameter space and therefore it was used in all subsequent work. In addition, we developed a quantum mechanical theoretical model of the CARS process to ensure proper understanding of our measurements. We demonstrated experimentally that mode excitation selectivity can be achieved using the pump fields extracted by the learning algorithm, and we explore the underlying selectivity mechanisms. Control of the relative phase of oscillation of different vibrational modes is also observed. Our work demonstrates coherent quantum control of all relevant aspects of the molecular vibrational dynamics of CO2. | en_ZA |
| dc.description.abstract | AFRIKAANSE OPSOMMING : In hierdie werk ondersoek ons die koherente beheer van koolstofdioksied (CO2) vibrasionele dinamika met behulp van koherente anti-Stokes Raman verstrooiing(KARV). Gedurende KARV word vibrasionele modusse opgewek deur middel van gestimuleerde Raman verstrooiing (GRV). Vervolgens meet n nou-bandwydte meet puls die molekulêre toestand asook die tydsontwikkeling van die golf-pakkie wat geskep is tydens opwekking. Deur een van die GRV velde spektraal te vervorm kan die vibrasionele dinamika beheer word. In hierdie werk is aanvaar dat die pomp puls struktuur wat sal lei tot 'n gewenste dinamika onbekend is. Om daardie struktuur te vind, word n leer algoritme ontwikkel wat n ruimtelike lig modulator (RLM) in 'n 4f-optiese opstelling gebruik om die pomp te vervorm. Beide 'n tyd-frekwensie voorstelling van die gevormde veld (bekend as die von Neumann basis) en 'n standaard Fourier voorstelling was getoets gedurende optimering van 'n tweede harmoniese opwekking (THO) in 'n BBO kristal om vas te stel wat die optimering probleem die beste sal pas in terme van konvergensie koers en parameter ruimte grootte. Daar is bevind dat die von Neumann basis vinniger konvergeer as die standaard Fourier verteenwoordiging terwyl dit op 'n groter parameter ruimte werk en is dus gebruik in alle werk wat daarop volg. Daarbenewens het ons 'n kwantummeganiese teoretiese model van die proses ontwikkel om behoorlike begrip van ons metings te verseker. Ons demonstreer eksperimenteel dat modus opwekking selektief gedoen kan word met behulp van die pomp velde verkry vanaf die leer algoritme, en ons ondersoek die onderliggende selektiwiteit meganismes. Beheer van die relatiewe fase van ossillasie van verskillende vibrasionele modusse is ook waargeneem. Ons werk toon kwantum beheer van alle relevante aspekte van die molekulêre vibrasionele dinamika van CO2. | af_ZA |
| dc.format.extent | xv, 128 pages : illustrations (mainly colour) | en_ZA |
| dc.identifier.uri | http://hdl.handle.net/10019.1/100836 | |
| dc.language.iso | en_ZA | en_ZA |
| dc.publisher | Stellenbosch : Stellenbosch University | en_ZA |
| dc.rights.holder | Stellenbosch University | en_ZA |
| dc.subject | Coherent control | en_ZA |
| dc.subject | Coherent anti-Stokes Raman spectroscopy | en_ZA |
| dc.subject | Vibrational excitation | en_ZA |
| dc.subject | Pulse shaping | en_ZA |
| dc.subject | Molecular vibration | en_ZA |
| dc.subject | UCTD | en_ZA |
| dc.title | Control of CO2 vibrational dynamics via shaped-pulse coherent anti-Stokes Raman spectroscopy | en_ZA |
| dc.type | Thesis | en_ZA |