Novel light sources and high-resolution interferometric applications

Igor Shavrin

Novel light sources and high-resolution interferometric applications

Julkaisun otsikon käännös: Novel light sources and high-resolution interferometric applications

Igor Shavrin

Tutkimustuotos: Doctoral Thesis › Collection of Articles

Abstrakti

Väitöskirjassa on tutkittu spektriltään laajakaistaisen valon, ns. superkontinuumivalon, aikaansaamista optisissa kuiduissa sekä kahta korkean erotuskyvyn optista interferometria-tekniikkaa. Superkontinuumivalo tuotetaan yleensä syöttämällä optiseen kuituun lyhyitä suuritehoisia, yksivärisiä laserpulsseja, jotka vuorovaikuttaessaan kuidussa tuottavat epälineaaristen optisten prosessien kautta spektriltään laajakaistaista pulssitettua valoa. Usein tarvitaan kuitenkin ajassa jatkuvaa emissiota. Työssä kehitettiin menetelmä, jossa valopulsseja levitetään aika-avaruudessa dispersiota hyväksi käyttäen siten, että vierekkäiset pulssit levenevät toistensa päälle. Näin onnistuttiin luomaan superkontinuumivaloa, jonka intensiteetti vaihteli alle 1 %. Voimakkaiden superkontinuumipulssien tuottamisessa monimuotokuidut ovat etusijalla yksimuotokuituihin verrattuna. Ne kestävät suurempia pulssitehoja ja korkeamman kerta- luvun muodot mahdollistavat uudet spektriominaisuudet. Näiden mahdollisuuksien tutkimiseksi kehitettiin numeerinen laskumenetelmä, jolla superkontinuumin syntyä monimuoto- kuiduissa voidaan simuloida. Menetelmää sovellettiin ulostulopulssien polarisaatiodynamiikan selvittämiseen tapauksessa, jossa ei-kahtaistaittavassa monimuotoisessa mikrorakennekuidussa etenee kaksi degeneroitunutta muotoa. Simulaatiotuloksia verrattiin myös kokeellisiin mittauksiin tapauksessa, jossa käytettiin erityisen ohutytimistä mikro- rakennekuitua. Korkeampien muotojen vaikutus kävi ilmeiseksi jo alhaisilla pumppaustehoilla. Sovelluksena laajakaistaisen valon käytölle työssä kehitettiin mittaussignaalin vaiheinformaatiota hyödyntävä stroboskooppinen valkoisen valon interferometri, jolla voitiin tutkia mikromekaanisten resonaattorien värähtelyominaisuuksia. Analyysimenetelmää kehittämällä kyettiin havaitsemaan alle 100 pikometrin värähtelyamplitudeja. Parhaaseen suorituskykyyn pääsemiseksi valolähteen spektriltä vaaditaan tiettyä leveyttä, joka pystyttiin toteuttamaan yksinkertaisella LEDillä. Koejärjestelyllä kyettiin mittaamaan värähtelyjäää aiemmin raportoitua korkeammilla taajuuksilla. Lopuksi väitöskirjassa esitetään optiseen interferometriaan perustuva kaasun taitekertoimen mittausmenetelmä, jossa kaasu vuorovaikuttaa onttoytimisessä fotonikidekuidussa etenevän, aallonpituudeltaan viritettävän laservalon kanssa. Mittaustuloksena saadaan sekä kaasun absorption että sen taitekertoimen spektrit suurella herkkyydellä. Esimerkkinä onnistuttiin mittaamaan ilma-asetyleeniseoksen taitekerroin 4•10-7 suuruisella erotuskyvyllä aallonpituus välillä 1525 - 1545 nm.

Julkaisun otsikon käännös	Novel light sources and high-resolution interferometric applications
Alkuperäiskieli	Englanti
Pätevyys	Tohtorintutkinto
Myöntävä instituutio	Aalto-yliopisto
Ohjaaja	Sopanen, Markku, Vastuuprofessori Ludvigsen, Hanne, Ohjaaja
Kustantaja	Aalto University
Painoksen ISBN	978-952-60-5472-8
Sähköinen ISBN	978-952-60-5473-5
Tila	Julkaistu - 2013
OKM-julkaisutyyppi	G5 Artikkeliväitöskirja

Tutkimusalat

superkontinuumivalo
monimuotokuitu
valkoisen valon interferometria

Pääsy asiakirjaan

http://urn.fi/URN:ISBN:978-952-60-5473-5

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@phdthesis{d7b935de5b31433e86f8b78dec42bbf3,

title = "Novel light sources and high-resolution interferometric applications",

abstract = "This thesis focuses on selected fundamental aspects of fiber-based supercontinuum ligh sources and presents two case studies of highresolution optical interferometry. Most commonly, supercontinuum light is generated by pulsed laser sources, so that strong intensity fluctuations are inherent in the emitted light. For applications, which require broadband continuouswave illumination, a new concept of a broadband light source based on dispersive stretching of supercontinuum light pulses is presented. This concept was found to be able to provide intensity fluctuations below 1 \% in the output light. Supercontinuum generation in multimode fibers involves two major aspects that make it differ from continuum generation in singlemode fibers; much higher powers can be obtained without damaging the fiber and different spectral properties become accessible with the higher-order modes. To explore these possibilities, a numerical solver for simulation studies of supercontinuum generation in multimode fibers was developed. First, the solver was used to demonstrate the polarization dynamics of the supercontinuum generated by two degenerate fiber modes in a non-birefringent microstructured fiber. Next, the operation of the solver was verified by comparing the simulated and measured supercontinua produced in a suspended-core fiber. The influence of the higher-order modes became apparent already at lower pump powers. As a case study of applications where broadband light sources are needed, an interferometer was developed to characterize surface vibrations in micro-mechanical resonators. The measurement principle was based on phase-shifting white-light interferometry (PS-WLI) with stroboscopic illumination. An analysis method was developed which made it possible to detect vibration amplitudes below 100 picometers. Further, it was found that for the best performance of PS-WLI an optimal spectral width of the illuminating light source is required, which in the presented setup was closely matched by a simple green light-emitting diode (LED). The pulse duration obtained from the LED allowed imaging out-of-plane vibration fields in a micromechanical plate resonator at frequencies up to 14 MHz, which is about 10 MHz higher than what has previously been reported. In principle, the achieved amplitude detection limit could allow even higher frequencies. Additionally, a simple interferometric gas refractometer based on a hollow-core photonic band-gap fiber was developed and characterized. Using a tunable laser source, spectrally resolved measurements of both the refractive index and the absorption coefficient of gaseous analytes could be measured with high sensitivity. With this device, the refractive index of an airacetylene mixture was measured with a resolution of 4•10-7 RIU (refractive index units) in the spectral range from 1525 nm to 1545 nm.",

keywords = "supercontinuum generation, multimode fibers, white-light interferometry, superkontinuumivalo, monimuotokuitu, valkoisen valon interferometria, supercontinuum generation, multimode fibers, white-light interferometry",

author = "Igor Shavrin",

year = "2013",

language = "English",

isbn = "978-952-60-5472-8",

series = "Aalto University publication series DOCTORAL DISSERTATIONS",

publisher = "Aalto University",

number = "204",

address = "Finland",

school = "Aalto University",

}

TY - BOOK

T1 - Novel light sources and high-resolution interferometric applications

AU - Shavrin, Igor

PY - 2013

Y1 - 2013

N2 - This thesis focuses on selected fundamental aspects of fiber-based supercontinuum ligh sources and presents two case studies of highresolution optical interferometry. Most commonly, supercontinuum light is generated by pulsed laser sources, so that strong intensity fluctuations are inherent in the emitted light. For applications, which require broadband continuouswave illumination, a new concept of a broadband light source based on dispersive stretching of supercontinuum light pulses is presented. This concept was found to be able to provide intensity fluctuations below 1 % in the output light. Supercontinuum generation in multimode fibers involves two major aspects that make it differ from continuum generation in singlemode fibers; much higher powers can be obtained without damaging the fiber and different spectral properties become accessible with the higher-order modes. To explore these possibilities, a numerical solver for simulation studies of supercontinuum generation in multimode fibers was developed. First, the solver was used to demonstrate the polarization dynamics of the supercontinuum generated by two degenerate fiber modes in a non-birefringent microstructured fiber. Next, the operation of the solver was verified by comparing the simulated and measured supercontinua produced in a suspended-core fiber. The influence of the higher-order modes became apparent already at lower pump powers. As a case study of applications where broadband light sources are needed, an interferometer was developed to characterize surface vibrations in micro-mechanical resonators. The measurement principle was based on phase-shifting white-light interferometry (PS-WLI) with stroboscopic illumination. An analysis method was developed which made it possible to detect vibration amplitudes below 100 picometers. Further, it was found that for the best performance of PS-WLI an optimal spectral width of the illuminating light source is required, which in the presented setup was closely matched by a simple green light-emitting diode (LED). The pulse duration obtained from the LED allowed imaging out-of-plane vibration fields in a micromechanical plate resonator at frequencies up to 14 MHz, which is about 10 MHz higher than what has previously been reported. In principle, the achieved amplitude detection limit could allow even higher frequencies. Additionally, a simple interferometric gas refractometer based on a hollow-core photonic band-gap fiber was developed and characterized. Using a tunable laser source, spectrally resolved measurements of both the refractive index and the absorption coefficient of gaseous analytes could be measured with high sensitivity. With this device, the refractive index of an airacetylene mixture was measured with a resolution of 4•10-7 RIU (refractive index units) in the spectral range from 1525 nm to 1545 nm.

AB - This thesis focuses on selected fundamental aspects of fiber-based supercontinuum ligh sources and presents two case studies of highresolution optical interferometry. Most commonly, supercontinuum light is generated by pulsed laser sources, so that strong intensity fluctuations are inherent in the emitted light. For applications, which require broadband continuouswave illumination, a new concept of a broadband light source based on dispersive stretching of supercontinuum light pulses is presented. This concept was found to be able to provide intensity fluctuations below 1 % in the output light. Supercontinuum generation in multimode fibers involves two major aspects that make it differ from continuum generation in singlemode fibers; much higher powers can be obtained without damaging the fiber and different spectral properties become accessible with the higher-order modes. To explore these possibilities, a numerical solver for simulation studies of supercontinuum generation in multimode fibers was developed. First, the solver was used to demonstrate the polarization dynamics of the supercontinuum generated by two degenerate fiber modes in a non-birefringent microstructured fiber. Next, the operation of the solver was verified by comparing the simulated and measured supercontinua produced in a suspended-core fiber. The influence of the higher-order modes became apparent already at lower pump powers. As a case study of applications where broadband light sources are needed, an interferometer was developed to characterize surface vibrations in micro-mechanical resonators. The measurement principle was based on phase-shifting white-light interferometry (PS-WLI) with stroboscopic illumination. An analysis method was developed which made it possible to detect vibration amplitudes below 100 picometers. Further, it was found that for the best performance of PS-WLI an optimal spectral width of the illuminating light source is required, which in the presented setup was closely matched by a simple green light-emitting diode (LED). The pulse duration obtained from the LED allowed imaging out-of-plane vibration fields in a micromechanical plate resonator at frequencies up to 14 MHz, which is about 10 MHz higher than what has previously been reported. In principle, the achieved amplitude detection limit could allow even higher frequencies. Additionally, a simple interferometric gas refractometer based on a hollow-core photonic band-gap fiber was developed and characterized. Using a tunable laser source, spectrally resolved measurements of both the refractive index and the absorption coefficient of gaseous analytes could be measured with high sensitivity. With this device, the refractive index of an airacetylene mixture was measured with a resolution of 4•10-7 RIU (refractive index units) in the spectral range from 1525 nm to 1545 nm.

KW - supercontinuum generation

KW - multimode fibers

KW - white-light interferometry

KW - superkontinuumivalo

KW - monimuotokuitu

KW - valkoisen valon interferometria

KW - supercontinuum generation

KW - multimode fibers

KW - white-light interferometry

M3 - Doctoral Thesis

SN - 978-952-60-5472-8

T3 - Aalto University publication series DOCTORAL DISSERTATIONS

PB - Aalto University

ER -

Novel light sources and high-resolution interferometric applications

Abstrakti

Tutkimusalat

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