Supercontinuum pulse characterisation and compression
Date
2017-03
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Stellenbosch : Stellenbosch University
Abstract
AFRIKAANSE OPSOMMING : In hierdie projek word die infrastruktuur van 'n hoë-resolusie nie-lineêre mikroskoop ontwikkel.
Spesifiek word daar gekyk na generering van breëband lig deur middel van 'n
fotoniese-kristalvesel (PCF) en 'n puls kompressor.
Polarisasie en drywing karaktereienskappe van die PCF word ondersoek om optimale
werks omstandighede vas te stel. Vir hierdie optimale werks omstandighede benodig ons
breëband lig met die hoogste drywing deursette. Afhangend van die pomp drywing, kan
die bandwydte van die lig van 12 nm tot sowat 200 nm verbreed. Dit stel ons instaat om
die pomp pulslengte van 80 fs na onder 10 fs saam te pers.
Vir die doeleindes van die projek is die 'multiphoton intrapulse interference phase
scan' of MIIPS die ideale metode om ons breëband pulse te karakteriseer en saam te pers.
Ons wys dat ons die toepaslikheid van hierdie metode numeries en eksperimenteel getoets
het. Ons het vasgestel vanaf ons simulasies dat ons in staat is om die fase verhoudings
van spektrale komponente vas te stel.
Eksperimente wat uitgevoer is met lig met 'n breëband van rondom 80 nm wys dat die
MIIPS algoritme in staat is om die superkontinue pulse se fase vas te stel en in die proses
die pulse saam te pers. `n Meting van die GVD van 'n blokkie SF6 glas met 'n bekende
dispersie is gebruik as bykomende inligting om die effektiwiteit van MIIPS te illustreer.
'n SLM IFROG meting is uitgevoer op die kort pulse as 'n toets hoe kort die pulse is
na 'n MIIPS meting. Hierdie metode het gewys dat die pulse lengte van die pikosekonde
regime na ∼ 23 fs saam gepers is. Hierdie pulse is naby aan die Fourier limiet van ∼ 12
fs vir hierdie bandwydte.
ENGLISH ABSTRACT : This project centers around the development of infrastructure, specifically a broadband white light source, for integration into non-linear microscopes. The broadband light source needed for such an instrument comprises an all-normal dispersion photonic crystal bre (ANDi PCF) (which produces a supercontinuum) and a pulse compressor (which produces the needed ultra short pulses). Polarisation and power characteristics of the ANDi PCF are investigated in order to establish the optimal working conditions with the broadest spectral output coinciding with the highest power throughput. The bandwidth can be increased from about 12 nm to 200 nm (depending on the pump power) and enables us to decrease the pump pulse length from about 80 fs to below 10 fs if we are able to fully compress the full bandwidth. A particularilly suitable pulse characterisation technique, multiphoton intrapulse interference phase scan (MIIPS), is used to characterise and compress the supercontinuum pulses produced by the PCF. The e cacy of this technique is computationally and experimentally tested through computer simulations and laboratory experiments. From the simulations we see that the MIIPS technique is able to adequately reconstruct the phase of the supercontinuum pulses which can then be used to compress the pulses. Experiments performed on bandwidths around ∼ 80 nm, show that the MIIPS algorithm is able to reconstruct the supercontinuum pulse's phase and in the process compress it. A measurement of the GVD of a SF6 glass cube with known dispersion is used as supplementary evidence of the e ectiveness of the MIIPS technique. A SLM assisted IFROG measurement is performed on the compressed pulses to further test the degree of compression after MIIPS. This measurement shows a decrease in pulse length from picosecond regime to ∼ 23 fs. This is near to the Fourier limit of ∼ 12 fs for these bandwidths
ENGLISH ABSTRACT : This project centers around the development of infrastructure, specifically a broadband white light source, for integration into non-linear microscopes. The broadband light source needed for such an instrument comprises an all-normal dispersion photonic crystal bre (ANDi PCF) (which produces a supercontinuum) and a pulse compressor (which produces the needed ultra short pulses). Polarisation and power characteristics of the ANDi PCF are investigated in order to establish the optimal working conditions with the broadest spectral output coinciding with the highest power throughput. The bandwidth can be increased from about 12 nm to 200 nm (depending on the pump power) and enables us to decrease the pump pulse length from about 80 fs to below 10 fs if we are able to fully compress the full bandwidth. A particularilly suitable pulse characterisation technique, multiphoton intrapulse interference phase scan (MIIPS), is used to characterise and compress the supercontinuum pulses produced by the PCF. The e cacy of this technique is computationally and experimentally tested through computer simulations and laboratory experiments. From the simulations we see that the MIIPS technique is able to adequately reconstruct the phase of the supercontinuum pulses which can then be used to compress the pulses. Experiments performed on bandwidths around ∼ 80 nm, show that the MIIPS algorithm is able to reconstruct the supercontinuum pulse's phase and in the process compress it. A measurement of the GVD of a SF6 glass cube with known dispersion is used as supplementary evidence of the e ectiveness of the MIIPS technique. A SLM assisted IFROG measurement is performed on the compressed pulses to further test the degree of compression after MIIPS. This measurement shows a decrease in pulse length from picosecond regime to ∼ 23 fs. This is near to the Fourier limit of ∼ 12 fs for these bandwidths
Description
Thesis (MSc)--Stellenbosch University, 2017
Keywords
Pulse compressors, Microscopy, Supercontinuum, Photonic crystal fibre (PCF), Multiphoton intrapulse interference phase scan (MIIPS), UCTD