Kyoto University (京都大学) / 0048 / 新制・課程博士 / 博士(工学) / 甲第16866号 / 工博第3587号 / 新制||工||1542(附属図書館) / 29541 / 京都大学大学院工学研究科材料化学専攻 / (主査)教授 平尾 一之, 教授 田中 勝久, 教授 三浦 清貴 / 学位規則第4条第1項該当

>Magister Scientiae - MSc / Recent research shows that the study of optical properties of organic material natural dyes has gained much consideration. The specific functional groups in several natural dyes remain essential for the large nonlinear absorption expressed in terms of nonlinear optical susceptibilities or other mechanism of absorption such as two photon absorption (TPA), reverse saturable absorption (RSA) or intensitydependent refractive index characteristic. In this thesis we highlight the optical limiting responses of selected natural dyes as nonlinear response in the femtosecond regime. This technique refers to the decrease of the transmittance of the material with the increased incident light intensity.Three dyes derived from beetroot, flame flower and mimosa flower dyes were investigated. The results showed a limiting behaviour around 795 mW for the beetroot and the flame dye while there is total transmission in the flame dye sample. The performance of the nonlinearity i.e. the optical limiting is related to the existence of alternating single and double bonds(i.e. C-C and C=C bonds) in the molecules that provides the material with the electron delocalization, but also it is related to the light intensity.Beside nonlinearity study, crystallographic investigation was carried out for more possible applicability of the selected dyes and this concerned only the mimosa and flame flower dye thin film samples since the beetroot thin film was very sensitive to strong irradiation (i.e. immediately destroyed when exposed to light with high intensity). For more stability,dye solutions were encapsulated in gels for further measurements.

Les microchip lasers à impulsions sub-nanosecondes peuvent être des alternatives intéressantes aux lasers à impulsions femtosecondes pour le micro-usinage des matériaux transparents par absorption multiphotonique. Ces lasers peuvent facilement atteindre les puissances crêtes nécessaires pour déclencher l'ablation de tous les matériaux, y compris les diamants, céramiques, plastiques, et des verres. En outre, ils sont de faible coût, avec un design compact et robuste. Dans cette thèse, un micro-chip laser Nd:YAG amplifié (532 nm, 300 ps) a été utilisé pour la micro-gravure et le marquage de différents types de matériaux transparents, comme le verre borosilicate D263, le verre BK7 et le thermoplastique SBS. L'analyse des résultats a montré un bon accord avec le modèle d'expulsion de matière suite à la génération d'un plasma provoqué par une absorption laser à deux photons. Une résolution sub-micronique de marquage a été obtenue à l'intérieur d'un verre de borosilicate. Des canaux microfluidiques pour capteurs optiques ont été gravés sur verre BK-7 comprenant des guides d'ondes réalisés par échange d'ionique. Des réseaux denses de micro-canaux ont été fabriqués à la surface de matériaux thermoplastiques avec une zone affectée par les effets thermiques limités à quelques micromètres. En conclusion, ce travail de thèse montre que l'utilisation de ce type de laser permet un micro-usinage de très haute résolution avec des effets thermiques limités. / Microchip lasers with sub-nanosecond pulses are attractive alternative to femtosecond lasers for micromachining in transparent materials by multiphoton absorption. These lasers can easily reach pulse peak powers that are needed to trigger ablation in all materials, including diamond, ceramics, plastics, and glasses. In addition, they are low cost with compact and rugged design. In this thesis, a microchip laser (532 nm, 300 ps) has been used for micro-engraving and marking different types of transparent materials such as borosilicate D263, BK7, and SBS thermoplastic. Experimental resultsare rationalized by the model of matter explosion following the plasma generation induced by the laser two-photon absorption. Sub-micron resolution embedded marking is demonstrated inside borosilicate glass. Micro fluidic channels for optical sensors are engraved on BK-7 glass with ion-doped waveguides. Arrays of dense micro channels are fabricated at the surface of thermoplastics with a zone affected by thermal effects limited to the micron range. In summary, this thesis demonstrates that this type of laser can be efficiently used for high-resolution micro-machining transparent materials with minimal thermal effects.

abstract: Due to the ever increasing relevance of finer machining control as well as necessary reduction in material waste by large area semiconductor device manufacturers, a novel bulk laser machining method was investigated. Because the cost of silicon and sapphire substrates are limiting to the reduction in cost of devices in both the light emitting diode (LED) and solar industries, and the present substrate wafering process results in >50% waste, the need for an improved ingot wafering technique exists. The focus of this work is the design and understanding of a novel semiconductor wafering technique that utilizes the nonlinear absorption properties of band-gapped materials to achieve bulk (subsurface) morphological changes in matter using highly focused laser light. A method and tool was designed and developed to form controlled damage regions in the bulk of a crystalline sapphire wafer leaving the surfaces unaltered. The controllability of the subsurface damage geometry was investigated, and the effect of numerical aperture of the focusing optic, energy per pulse, wavelength, and number of pulses was characterized for a nanosecond pulse length variable wavelength Nd:YAG OPO laser. A novel model was developed to describe the geometry of laser induced morphological changes in the bulk of semiconducting materials for nanosecond pulse lengths. The beam propagation aspect of the model was based on ray-optics, and the full Keldysh multiphoton photoionization theory in conjuncture with Thornber's and Drude's models for impact ionization were used to describe high fluence laser light absorption and carrier generation ultimately resulting in permanent material modification though strong electron-plasma absorption and plasma melting. Although the electron-plasma description of laser damage formation is usually reserved for extremely short laser pulses (<20 ps), this work shows that it can be adapted for longer pulses of up to tens of nanoseconds. In addition to a model describing damage formation of sub-band gap energy laser light in semiconducting and transparent crystalline dielectrics, a novel nanosecond laser process was successfully realized to generate a thin plane of damage in the bulk of sapphire wafers. This was accomplished using high numerical aperture optics, a variable wavelength nanosecond laser source, and three-dimensional motorized precision stage control. / Dissertation/Thesis / Doctoral Dissertation Electrical Engineering 2015

>Magister Scientiae - MSc / Recent research shows that the study of optical properties of organic material natural dyes has gained much consideration. The specific functional groups in several natural dyes remain essential for the large nonlinear absorption expressed in terms of nonlinear optical susceptibilities or other mechanism of absorption such as two photon absorption (TPA), reverse saturable absorption (RSA) or intensitydependent refractive index characteristic. In this thesis we highlight the optical limiting responses of selected natural dyes as nonlinear response in the femtosecond regime. This technique refers to the decrease of the transmittance of the material with the increased incident light intensity.Three dyes derived from beetroot, flame flower and mimosa flower dyes were investigated. The results showed a limiting behaviour around 795 mW for the beetroot and the flame dye while there is total transmission in the flame dye sample. The performance of the nonlinearity i.e. the optical limiting is related to the existence of alternating single and double bonds (i.e. C-C and C=C bonds) in the molecules that provides the material with the electron delocalization, but also it is related to the light intensity.Beside nonlinearity study, crystallographic investigation was carried out for more possible applicability of the selected dyes and this concerned only the mimosa and flame flower dye thin film samples since the beetroot thin film was very sensitive to strong irradiation (i.e. immediately destroyed when exposed to light with high intensity). For more stability,dye solutions were encapsulated in gels for further measurements.

<p> 3D printing has established itself as a critical tool for manufacturing in all areas. It has evolved from a purely rapid prototyping technique into a feasible process for large-scale processing. A wide variety of 3D printing processes exist across an extreme range of size, from meters to nanometers. Much of the current technological advances come from pushing fabrication techniques to smaller and smaller scales. For 3D printing this has led to the rise of two-photon polymerization, a direct laser writing process with submicron structuring capabilities. Two-photon polymerization has proven its worth as a nanoscale 3D fabrication technique but is often considered slow and expensive, two undesirable qualities for high throughput manufacturing. Parallelization methods such as projection lithography are potential solutions to increasing the throughput capabilities of two-photon polymerization 3D printing. Additionally, the drive for further reducing the print size has inspired printing resolution enhancing strategies in two-photon polymerization printing by processes such as stimulated emission depletion (STED) and other STED-inspired pathways. This work will explore avenues for improving two-photon polymerization printing throughput and resolution.</p> <p> First, a two-photon polymerization printing system is constructed with a secondary laser for controlling polymerization inhibition. Through a STED process, a 65 nm wide printed line feature was achieved. Alongside this, a characterization and verification methodology for choosing new photoinitiator molecules for similar inhibition lithography processes is presented. Through implementation of tests such as Z-scan, fluorescence depletion, ultrafast transient spectroscopy and UV-Vis absorption and fluorescence measurements a promising new photoinitiator with 5-factor improvement in printing efficiency is found. </p> <p> Second, a projection lithography scheme is developed for rapid two-photon 3D printing. A digital micro-mirror device (DMD) is utilized for dynamic pattern generation and the effects of its dispersion properties are considered. Through a spatiotemporal focusing process, continuous 3D printing is achieved at vertical prints speeds of 1 mm s-1. Simulations performed representing this rapid printing process indicate a ~1 µm layer print feature size for large areas of exposure. Comparably, a printed vertical feature size of ~ 1 µm was achieved. Lateral feature sizes ~200 nm were also demonstrated in fabrication. A variety of complex 3D structures are printed for demonstration of the spatiotemporal focusing projection lithography process including millimeter scale objects with micrometer scale 3D features.</p> <p> Finally, resolution enhancing strategies are implemented into the continuous, projection two-photon lithography technique. An investigation of the inhibition properties of a variety of photoinitiator systems for inhibiting polymerization achieved with low repetition rate laser exposure is presented. A planar polymerization inhibiting region is generated by creating a light sheet propagating perpendicularly to the projection printing plane. </p>

Nesta tese estudamos a relação entre as propriedades de absorção de multi-fótons e a estrutura molecular de três classes distintas de compostos orgânicos &pi;-conjugados: derivados de vitamina A, complexos de platina acetilada e compostos quirais. Materiais orgânicos emergiram nas últimas décadas como candidatos para aplicações em dispositivos fotônicos, principalmente aqueles envolvendo processos de absorção multifotônica, uma vez que suas propriedades podem ser facilmente otimizadas através de engenharia molecular. Devido às diferenças inerentes entre as estruturas químicas dos compostos aqui investigados, foi possível verificar individualmente a influência do comprimento de conjugação, da presença de grupos doadores e aceitadores de elétrons (estruturas push-pull), da planaridade molecular e de efeitos de comprimento de ligação sobre a seção de choque de absorção multifotônica. Para tanto, foram utilizadas as técnicas de Varredura-Z convencional e com contínuo de luz branca, espectroscopia de fluorescência por absorção de multi-fótons e fluorescência resolvida no tempo. Para correlacionar as propriedades moleculares com os espectros não-lineares, foram utilizados cálculos de química quântica em conjunto com o modelo de soma de estados essenciais. Através desse modelo foi possível associar aspectos puramente moleculares, como o momento de dipolo de transição, o momento de dipolo estático, a força do oscilador e a largura de linha dos estados eletrônicos com a estrutura molecular dos cromóforos, visando futuras aplicações tecnológicas. Resultados de espectroscopia de absorção de dois fótons revelaram que os derivados da vitamina A, como o trans-&beta;-apo-8-carotenal e all-trans &beta;-caroteno, possuem magnitudes da seção de choque extremamente elevadas (~5000 GM), indicando-os como materiais promissores para armazenamento óptico 3D. Os complexos de platina acetilada apresentaram características impares para aplicações em dispositivos de limitação de potência óptica baseados em processos de absorção de dois e três fótons como, elevadas absortividades não-lineares, boa transparência óptica, baixo limiar de limitação, alto intervalo dinâmico e rápido tempo de resposta. Por fim, os compostos quirais abriram possibilidades de explorar novos efeitos em óptica não-linear como, por exemplo, efeito de dipolo magnético e quadrupolo elétrico, apenas modificando o estado de polarização da luz. / In this thesis we studied the relationship between the multi-photon absorption properties and the molecular structure of three distinct classes of &pi;-conjugated organic compounds: derivatives of vitamin A, platinum acetylide complexes and chiral compounds. Organic materials have emerged as potential candidates for applications involving multiphoton absorption, since their properties can be changed through molecular engineering. Because of the inherent differences between the molecular structures of the compounds investigated here, it was possible to verify the influence of conjugation length, electron donor and acceptors groups (push-pull structures), molecular planarity and effects of bond length alternation on the multi-photon absorption cross-section. To investigate such properties, we have employed the conventional and white-light continuum femtosecond Z-scan technique and multi-photon and time-resolved fluorescence spectroscopy. We have also employed quantum chemical calculation and the essential sum-over-states approach to correlate the impact of molecular properties on the nonlinear spectra. It was possible to link pure molecular features such as transition dipole moment, static dipole moment, oscillator strength and states linewidth with the chromophores structures, aiming at future applications. The two-photon absorption spectroscopy results revealed that the derivatives of vitamin A, such as trans-&beta;-apo-8-carotenal and all-trans &beta;-carotene, present cross-sections values extremely high (~ 5000 GM), indicating them as promising materials for 3D optical storage. The platinum acetylide complexes can be applied in optical power limiting devices based on the two- and three-photon absorption process, since they present unique features, such as high nonlinearity, good optical transparency, low threshold limit, high dynamic range and fast response time. Finally, the chiral compounds opened up new possibilities to be explored in nonlinear optics, such as the effect of magnetic dipole and electric quadrupole, only manipulating the polarization state of the light.

Nesta tese estudamos a relação entre as propriedades de absorção de multi-fótons e a estrutura molecular de três classes distintas de compostos orgânicos &pi;-conjugados: derivados de vitamina A, complexos de platina acetilada e compostos quirais. Materiais orgânicos emergiram nas últimas décadas como candidatos para aplicações em dispositivos fotônicos, principalmente aqueles envolvendo processos de absorção multifotônica, uma vez que suas propriedades podem ser facilmente otimizadas através de engenharia molecular. Devido às diferenças inerentes entre as estruturas químicas dos compostos aqui investigados, foi possível verificar individualmente a influência do comprimento de conjugação, da presença de grupos doadores e aceitadores de elétrons (estruturas push-pull), da planaridade molecular e de efeitos de comprimento de ligação sobre a seção de choque de absorção multifotônica. Para tanto, foram utilizadas as técnicas de Varredura-Z convencional e com contínuo de luz branca, espectroscopia de fluorescência por absorção de multi-fótons e fluorescência resolvida no tempo. Para correlacionar as propriedades moleculares com os espectros não-lineares, foram utilizados cálculos de química quântica em conjunto com o modelo de soma de estados essenciais. Através desse modelo foi possível associar aspectos puramente moleculares, como o momento de dipolo de transição, o momento de dipolo estático, a força do oscilador e a largura de linha dos estados eletrônicos com a estrutura molecular dos cromóforos, visando futuras aplicações tecnológicas. Resultados de espectroscopia de absorção de dois fótons revelaram que os derivados da vitamina A, como o trans-&beta;-apo-8-carotenal e all-trans &beta;-caroteno, possuem magnitudes da seção de choque extremamente elevadas (~5000 GM), indicando-os como materiais promissores para armazenamento óptico 3D. Os complexos de platina acetilada apresentaram características impares para aplicações em dispositivos de limitação de potência óptica baseados em processos de absorção de dois e três fótons como, elevadas absortividades não-lineares, boa transparência óptica, baixo limiar de limitação, alto intervalo dinâmico e rápido tempo de resposta. Por fim, os compostos quirais abriram possibilidades de explorar novos efeitos em óptica não-linear como, por exemplo, efeito de dipolo magnético e quadrupolo elétrico, apenas modificando o estado de polarização da luz. / In this thesis we studied the relationship between the multi-photon absorption properties and the molecular structure of three distinct classes of &pi;-conjugated organic compounds: derivatives of vitamin A, platinum acetylide complexes and chiral compounds. Organic materials have emerged as potential candidates for applications involving multiphoton absorption, since their properties can be changed through molecular engineering. Because of the inherent differences between the molecular structures of the compounds investigated here, it was possible to verify the influence of conjugation length, electron donor and acceptors groups (push-pull structures), molecular planarity and effects of bond length alternation on the multi-photon absorption cross-section. To investigate such properties, we have employed the conventional and white-light continuum femtosecond Z-scan technique and multi-photon and time-resolved fluorescence spectroscopy. We have also employed quantum chemical calculation and the essential sum-over-states approach to correlate the impact of molecular properties on the nonlinear spectra. It was possible to link pure molecular features such as transition dipole moment, static dipole moment, oscillator strength and states linewidth with the chromophores structures, aiming at future applications. The two-photon absorption spectroscopy results revealed that the derivatives of vitamin A, such as trans-&beta;-apo-8-carotenal and all-trans &beta;-carotene, present cross-sections values extremely high (~ 5000 GM), indicating them as promising materials for 3D optical storage. The platinum acetylide complexes can be applied in optical power limiting devices based on the two- and three-photon absorption process, since they present unique features, such as high nonlinearity, good optical transparency, low threshold limit, high dynamic range and fast response time. Finally, the chiral compounds opened up new possibilities to be explored in nonlinear optics, such as the effect of magnetic dipole and electric quadrupole, only manipulating the polarization state of the light.

L'objet de cette thèse est l'étude de l'interaction d'un laser femtoseconde avec un support photosensible particulier: un verre phosphate dopé à l'argent appelé verre photo-luminescent (PL). Une nouvelle approche permettant de réaliser en trois dimensions dans un verre PL des nanostructures d'argent aux dimensions bien inférieures à la limite de diffraction est tout d'abord présentée. La mesure des propriétés optiques et structurales pour différentes échelles (spatiales et temporelles) a permis de proposer un mécanisme de formation des structures photo-induites qui est basé sur un jeu subtil entre les phénomènes d’absorption non-linéaire et de thermo-diffusion. La deuxième partie de cette thèse sera orientée sur les propriétés optiques (linéaires et non-linéaires) et les applications des ces nanostructures d’argent. En particulier, l’exaltation des propriétés non-linéaires des agrégats d’argent sera exploitée pour stocker optiquement de l’information en trois dimentions. / The aim of this work is the study of the interaction between a femtosecond laser and a special photosensitive medium: a silver containing phosphate glass, also called photo-luminescent (PL) glass. A new approach allowing to write, inside the PL glass, 3D silver nanostructures with feature size down to the diffraction limit is presented. Based on optical and structural measurments at different time and spacial scales, the mechanism of the formation of these nanostructures is described. A subtle interplay between nonlinear absorption and thermo-diffusion effects is found to be the key of the mechanism. The second part of this work relies on the optical properties (linear and nonlinear) and few applications of the silver nanostructures. More particulary, the enhancement of their nonlinear properties is used for three dimentional optical data storage.

Broadband spectral content is required to support ultrashort pulses. However this broadband content is subject to dispersion and hence the pulse duration of corresponding ultrashort pulses may be stretched accordingly. I used a commercially-available adaptive ultrashort pulse shaper featuring multiphoton intrapulse interference phase scan technology to characterise and compensate for the dispersion of the optical system in situ and conducted experimental and theoretical studies in various inter-linked topics relating to the light-matter interaction. Firstly, I examined the role of broadband ultrashort pulses in novel light-matter interacting systems involving optically co-trapped particle systems in which inter-particle light scattering occurs between optically-bound particles. Secondly, I delivered dispersion-compensated broadband ultrashort pulses in a dispersive microscope system to investigate the role of pulse duration in a biological light-matter interaction involving laser-induced cell membrane permeabilisation through linear and nonlinear optical absorption. Finally, I examined some of the propagation characteristics of broadband ultrashort pulse propagation using a computer-controlled spatial light modulator. The propagation characteristics of ultrashort pulses is of paramount importance for defining the light-matter interaction in systems. The ability to control ultrashort pulse propagation by using adaptive dispersion compensation enables chirp-free ultrashort pulses to be used in experiments requiring the shortest possible pulses for a specified spectral bandwidth. Ultrashort pulsed beams may be configured to provide high peak intensities over long propagation lengths, for example, using novel beam shapes such as Bessel-type beams, which has applications in biological light-matter interactions including phototransfection based on laser-induced cell membrane permeabilisation. The need for precise positioning of the beam focus on the cell membrane becomes less strenuous by virtue of the spatial properties of the Bessel beam. Dispersion compensation can be used to control the temporal properties of ultrashort pulses thus permitting, for example, a high peak intensity to be maintained along the length of a Bessel beam, thereby reducing the pulse energy required to permeabilise the cell membrane and potentially reduce damage therein.