Dissertations / Theses on the topic 'Gradient index optics'

ITC/USA 2011 Conference Proceedings / The Forty-Seventh Annual International Telemetering Conference and Technical Exhibition / October 24-27, 2011 / Bally's Las Vegas, Las Vegas, Nevada
There are a myriad of applications for terahertz radiation: security, military radar, product inspection, and telecommunications. These require manipulation of the radiation beyond simple transmission and detection, namely refraction: focusing, defocusing, and collimation. The current state of the art fabrication of terahertz lenses is an expensive and time consuming processes; involving high purity semiconductors and months of lead time. Our project focused on demonstrating that an inexpensive and quick process could reduce the production investment required by more than three orders of magnitude. This process is based on fabrication using a novel gradient index structure produced with polymer-jetting rapid-prototyping machine.

Les cristaux photoniques à gradient (CPG) permettent une ingénierie de leur indice effectif, ce qui offre de nouveaux degrés de liberté pour la conception de dispositifs photoniques. Ils s’appréhendent par l’optique à gradient d’indice (GRIN optics), qui décrit des milieux inhomogènes dans lesquels la lumière ne se propage pas rectilignement. Il est ainsi possible d’envisager tout profil d’indice. Les CPG sont donc particulièrement attractifs pour la miniaturisation des composants optiques, notamment en photonique sur Silicium. Ils sont fondés sur la variation d’un paramètre de la maille élémentaire du cristal photonique (CP); ici, c’est le facteur de remplissage qui varie afin que l’indice effectif du CPG réalise le profil d’indice souhaité. Le but de cette thèse est d’explorer le potentiel des CPG en concevant des dispositifs à gradient d’indice sur la "plateforme" Silicium sur isolant (SOI) aux longueurs d’onde pour les télécommunications. C’est la chaine complète qui va de la conception à la caractérisation du dispositif, en passant par la simulation et la fabrication, qui est mise en œuvre. Nous nous sommes principalement concentrés sur deux instruments typiques de l’optique à gradient d’indice : la lentille de Mikaelian et le Half Maxwell Fish Eye (HMFE). Dans cette thèse, nous proposons une nouvelle méthode d’approximation de l’indice effectif adaptée à la "plateforme" SOI, que nous avons validée en concevant une lentille de Mikaelian (à profil d’indice sécante hyperbolique). Pour de tels dispositifs, il faut en effet tenir compte de deux indices effectifs : celui du mode guidé dans la couche de Silicium et celui du CP. Dans cette méthode, l’indice effectif du CP est d’abord calculé pour remplacer l’indice de la couche du mode guidé ; puis l’indice effectif de cette couche est calculé. Les résultats de simulation obtenus au moyen d’un logiciel commercial (méthode FDTD) montrent que la lentille ainsi conçue satisfait les prévisions analytiques, contrairement à ce que donnent les méthodes couramment utilisées. Nous l’avons alors appliquée au HMFE. Les dispositifs ont ensuite été fabriqués en salle blanche par lithographie par faisceau d’électrons (EBL) et par gravure plasma (ICP). Les différents CPG fabriqués consistent en des trous d’air répartis périodiquement dans la couche de Silicium, dont le diamètre minimal est d’environ 40 nm. Puis, ils ont été caractérisés en deux temps, notamment par microscopie en champ proche (SNOM). L’épaisseur de ces dispositifs est de quelques longueurs d’onde (3 ou 5 λ_0 environ), tandis la largeur de leur tâche focale est proche de la limite de diffraction (0.5 λ_0 environ). Ils fonctionnent sur une plage de longueurs d’onde de 150 nm environ. Les résultats de la lentille de Mikaelian ont été utilisés pour développer un convertisseur de taille de mode (taper) effectif sur quelques longueurs d’onde. Il est dix fois plus court qu’un convertisseur classique. Dans cette thèse, nous montrons aussi comment il est possible d’interpréter la propagation de l’onde EM dans ces composants à gradient d’indice sur "plateforme" SOI au moyen du principe de l’interféromètre multimode. En se propageant, les différents modes accumulent une différence de phase, qui se traduit par un battement qui modifie la distribution du champ EM, conduisant à la focalisation. La longueur caractéristique de ce battement est égale à la distance focale. Tous ces dispositifs sont étudiés pour s’intégrer dans des circuits de photonique intégrée
Gradient photonic crystals (GPhCs) enable the engineering of their effective index, opening up new degrees of freedom in photonic device design. They can be understood through gradient index optics (GRIN optics), which describe inhomogeneous media in which light does not propagate along straight paths. This makes it possible to consider any index profile. This makes GPhCs particularly attractive for the miniaturization of optical components, especially in silicon photonics. They are based on the variation of a parameter of the photonic crystal elemental cell (PhC); here, the filling factor is varied so that the effective index of the GPhC achieves the desired index profile. The aim of this thesis is to explore the potential of GPhCs by designing graded-index devices on the Silicon-On-Insulator (SOI) "platform" at telecom wavelengths. The complete chain from design to device characterization, including simulation and manufacturing, is implemented. We focused on two typical gradient index optics instruments: the Mikaelian lens and the Half Maxwell Fish Eye (HMFE). In this thesis, we propose a new effective index approximation method for the SOI "platform", which we have validated by designing a Mikaelian lens (with a hyperbolic secant index profile). For such devices, two effective indices need to be taken into account: that of the guided mode in the Silicon layer and that of the PhC. In this method, the effective index of the PhC is first calculated to replace the index of the guided mode layer; then the effective index of this layer is calculated. Simulation results obtained using commercial software (FDTD method) show that the lens designed in this way satisfies the analytical predictions, contrary to the results obtained with commonly used methods. We then applied it to HMFE.The devices were then fabricated in the cleanroom by electron beam lithography (EBL) and plasma etching (ICP). The individual GPhCs consisted of periodically distributed air holes in the Silicon layer, with a minimum diameter of around 40 nm. They were then characterized in two stages, notably by near-field microscopy (SNOM). These devices are only a few wavelengths thick (approx. 3 or 5 λ_0), while their focal spot width is close to the diffraction limit (approx. 0.5 λ_0). They operate over a wavelength range of around 150 nm. The Mikaelian lens results have been used to develop a mode size converter (taper), which is effective over a few wavelengths. It is ten times shorter than a conventional converter. In this thesis, we also show how it is possible to interpret EM wave propagation in these graded-index components on the SOI platforms using the multimode interferometer principle. As they propagate, the different modes accumulate a phase difference, resulting in a mode beat that modifies the EM field distribution, leading to focusing. The characteristic length of this mode beat is equal to the focal length. All these devices are studied for integration into integrated photonics circuits

The human eye is a complex optical system comprised of many components. The crystalline lens, an optical component with a gradient index (GRIN), is perhaps the least understood as it is situated inside the eye and as a result is difficult to characterize. Its complex nonlinear structure is not easily measured and consequently not easily modeled. Presently several models of the GRIN structure exist describing the average performance of crystalline lenses. These models, however, do not accurately describe the performance of crystalline lenses on an individual basis and a more accurate individual eye model based on anatomical parameters is needed. This thesis proposes an anatomically correct, individually customizable crystalline lens model. This is an important tool and is needed both for research on the optical properties of human eyes and to diagnose and plan the treatment of optically based visual problems, such as refractive surgery planning. The lens model consisted of an interior GRIN with a constant refractive index core. The anterior and posterior surface was described by conic sections. To realize this eye model, the optical and biometric properties of mammalian lenses were measured and the correlation relationships between these measurements were used to simplify the model down to one fitting parameter which controls the shape of the GRIN. Using this data, an anatomically correct individualizable model of the lens was successfully realized with varying parameters unique to each lens. Using this customizable lens model, customizable human eye models based on measurements of the entire human eye can be realized.

The main goal of this thesis is the numerical and experimental verification of the concept of the structured micro-optical elements fabricated with the modified stackand- draw technique. This technology, based on the well-known method of photonic crystal fibres (PCFs) production, allows the fabrication of nanostructured GRIN microlenses, form birefringent nanostructured materials and diffractive optical elements (DOEs). The principle of operation of the nanostructured GRIN (nGRIN) microlenses as well as the form birefringent nanostructured material can be explained by an effective medium theory (EMT). Both the approach based on the Maxwell-Garnet formula used for a description of nanostructured GRIN microlenses and the second-order EMT needed to account for birefringence properties are introduced. Numerical simulations of a Gaussian beam focusing and collimation (within GRIN microlenses) are performed using a FDTD method. The modelling results show that nGRIN microlenses can be described using the notion of the effective permittivity (or the effective refractive index) also in the case of the Gaussian beam illumination. Futhermore, Gaussian beam propagation within nGRIN microlenses can be approximately described by the paraxial scalar theory of the GRIN medium despite a high refractive index gradient. The concept of a so-called large-diameter nGRIN microlens with a quantised refractive index profile is introduced. Numerical simulations, performed using fast Fourier transform beam propagation method (FFT-BPM), show that focusing properties of the large-diameter quantised nGRIN microlens are similar to the focusing characteristic of the corresponding ideal continuous GRIN microlens. Both simulation and experimental results show that the fabricated large-diameter quantised nGRIN microlens has good chromatic properties in a range 633nm - 850nm. The successful fabrication of the prototype birefringent nanostructured element and a few diffractive checkerboards structures with different feature sizes is also reported. Applicability of the second-order EMT in the case of the fabricated birefringent material is verified both numerically, using the FDTD method, and experimentally. Diffractive patterns produced by DOEs are shown.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2015.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 103-106).
Gradient index (GRIN) materials offer the most general manipulation over wave fields of light compared to conventional refractive optics, where the light is deflected by the curved surface. The creative way to implementing GRIN optics is to construct a subwavelength structure with the electromagnetic characteristics that are unavailable via the natural material. This artificial GRIN structure also known as "metamaterial" can be classified into two general categories: film and slab GRIN optics, depending on the propagation direction of light penetrating through or propagating along the metamaterial. In this dissertation, two different purposes of all-dielectric GRIN optics on (1) film: light extraction enhancement of the scintillator; (2) slab: aberration-free focusing using Lüneburg lens, are both investigated. The scintillator made by ceramics like Lutetium Yttrium Orthosilicate (LYSO) possesses higher index of refraction at 1.82 than the surrounding environment, which causes extraction loss due to index mismatching and total internal reflection (TIR) from scintillator to photodetector. A hybrid structure including two-dimensional photonic slab covered by the nanocone structure on the top was devised to recycle the energy loss from TIR and to create an index-matching layer in between. Design parameters of the hybrid structure were optimized by the simulation based on rigorous coupled-wave analysis, and the fabrication of hybrid structure was patterned by nanospheres (for nanocone structure) and laser interference (for photonic slab) lithography, respectively. Reactive ion etching (RIE) facilitated pattern transfer after two separate lithography processes. Finally, the characterization of nanostructured scintillator was performed with the ionizing source. The rest of this research focuses on the implementation of the slab GRIN optics: Nanostructured Lüneburg lens. The Lineburg lens is an aberration-free lens that can perfectly focus light on the opposite edge of the lens area, and such property can be used for light coupling from fiber to waveguide in the Silicon photonics. We designed the nanostructured Lineburg lens on the silicon-on-insulator substrate using effective index of refraction computed by photonic band theory, and the fabrication was carried out by the e-beam lithography and RIE process. The device characterized by near-field scanning optical microscopy exhibited the single focusing behavior under fundamental mode illumination via the intensity map over the lens region. In addition, the bi-foci phenomenon under higher order mode illumination was also revealed in the finite difference time domain simulation, and the ray picture for explaining the bi-foci was also included using Wigner distribution function and Hamiltonian ray-tracings.
by Chih-Hung Hsieh.
Ph. D.

This thesis proposes and tests an individually customizable model of the human crystalline lens. This model will be crucial in developing both research on the human eye and driving diagnostic tools to help plan and treat optical issues, such as those requiring refractive surgery. This thesis attempts to meet two goals: first, it will determine whether this new lens model can reproduce the major aberrations of real human eyes using a computational framework. Second, it will use clinical information to measure how well this model is able to predict post-operation results in refractive surgery, attempting to meet clinical standards of error. The model of the crystalline lens proposed within this thesis is shown to be valid, as it is able to both reproduce individual patient's optical information, and correctly predicts the optical results of a refractive surgery of an individual human eye within clinical standards of error.

Thesis (Ph.D.)--Case Western Reserve University, 2009
Abstract Department of Macromolecular Science and Engineering Title from PDF (viewed on 16 April 2009) Available online via the OhioLINK ETD Center

Ce mémoire présente l'étude d'un capteur chimique à fibre optique à gradient d'indice inversé basé sur la résonance de plasmons de surface. Des dispositifs optiques à prisme ou mettant en jeu des fibres optiques classiques en silice utilisant cette technique de mesure sont déjà commercialisés. L'objectif de notre travail a été de caractériser théoriquement et expérimentalement un nouveau type de fibre optique permettant d'accroître les performances de ce capteur et d'en simplifier l'instrumentation. Un état de l'art des capteurs à plasmons de surface est présenté. Les structures basées sur une fibre optique (unimodale, multimodale) font l'objet d'une présentation détaillée mettant en évidence les caractéristiques des montages employés ainsi que leurs performances respectives. Nous avons cherché à déterminer le profil d'indice de réfraction du cœur de la fibre rendant les angles d'incidence à l'interface cœur-gaine quasiment égaux quels que soient les rayons se propageant dans la fibre. Ceci a été réalisé en utilisant une source lumineuse ponctuelle monochromatique positionnée dans l'axe et à une distance définie de l'entrée de la fibre. Le profil idéal présente un gradient d'indice inversé très proche d'un profil parabolique inversé pour lequel l'indice est minimal au centre du cœur de la fibre. Une description des caractéristiques de cette fibre comprenant l'étude de la propagation des rayons a été réalisée. Le phénomène de plasmon de surface est ensuite décrit, de manière générale puis ses conditions d'excitation dans la fibre employée sont étudiées. Une étude expérimentale et théorique a été menée sur les paramètres les plus influents du capteur (nature et épaisseur du métal, position de la source ...). La présentation de deux applications pratiques (détection de traces de toluène dans un milieu aqueux et étude en temps réel du mécanisme de formation d'une monocouche auto-assemblée) montre les champs d'applications du dispositif optique simple développé.

Differentes methodes de calcul des proprietes optiques des couches minces optiques a profil d'indice continu sont presentees. Dans le cas des filtres rugates, l'utilisation de methodes analytiques a notamment permis un calcul des enveloppes des spectres ainsi que l'optimisation du profil d'indice. Un nouveau systeme de coevaporation sous vide a ete developpe pour realiser des filtres a profil d'indice continu. Des couches minces homogenes de zns, znse, mgf#2, ainsi que de zns-mgf#2 et de znfe-mgf#2 de differentes compositions ont ete realisees. Il apparait que le zns presente un probleme de condensation lorsqu'il est codepose avec du mgf#2, meme sur substrat froid. Le znse ne presente pas ce probleme lorsque celui-ci est majoritaire dans un melange realise a froid. Des filtres rugates a profil d'indice sinusoidal, comportant jusqu'a 20 periodes, ont ete realises en znse-mgf#2 depose sur substrat froid. Leurs spectres de reflexion et de transmission sont conformes aux simulations numeriques. Un atout important des filtres rugates par rapport aux multicouches a par ailleurs ete mis en evidence: les faibles contraintes dans les couches de melanges znse-mgf#2 et dans les filtres realises devraient autoriser la realisation de films epais, ce qui est une necessite pour la realisation de miroirs de faible largeur de bande

Four innovations in the fields of optical design and solar concentration are presented: a) the derivation of fundamentally new gradient-index (GRIN) distributions for perfect optical instruments. For the first time, GRIN lenses for visible and solar radiation with refractive index distributions that are amenable to current fabrication techniques are presented. Those lenses perform at nature's cardinal limits (within the geometrical optics approximation - valid for essentially all solar applications), i.e. perfect imaging and ideal nonimaging performance for monochromatic radiation and unprecedented image fidelity and near-ideal flux concentration for the full solar spectrum. Until now, there have been no GRIN solutions (for performance approaching the fundamental limits of flux concentration and image fidelity) that can accommodate an extended constant-index core - especially relevant because the only available fabrication techniques for visible and solar GRIN lenses require a constant-index core. b) The design, for the first time, of a nominally stationary solar concentrator with attainable geometric concentration of the order of 10super suns with high collection efficiency. The burden of tracking is transferred inside the stationary module where mm-scale motion of GRIN perfect imaging lenses tracks the sun. This creates the possibility for rooftop Concentrator Photovoltaics (CPV) with unprecedented optical performance and exceptional optical tolerance. c) The design of a nominally stationary solar concentrator with a modified Simultaneous Multiple Surface technique for nonimaging contoured lenses with flux concentration of the order of tenths of suns. d) The design of planar GRIN lenses able to deliver flux concentrations close to the thermodynamic limit to Solar Concentration with a single, optical element, previously deemed unattainable and particularly suitable to dual-axis tracking CPV.

碩士
國立清華大學
動力機械工程學系
105
Gradient Index Lens (abbreviated as GRIN Lens) is based on optic theory of refractive index distribution in optical material to achieve the optical performances of a lens. For the cases of flat GRIN Lens, positive and negative power optical lenses are made by varying the refractive index distribution in the lenses. Compared with conventional lenses rely on the spherical surfaces to refract light rays, GRIN Lenses can reduce the number of lenses used in lens modules and simplify the lens assembly. This thesis is devoted to the theory of distribution in refractive index in GRIN lenses with aberrations analysis and measurement of the GRIN lenses. Initially, with 2.0 mm focal length and 0.5 mm length thickness, the GRIN lens is designed with a clear aperture radius being 0.2 mm. Through the design of radial (vertical the optical axis) and axial (along the optical axis) gradient refractive index distribution of lens, the axial chromatic aberration of GRIN lens in visible light spectrum is optimized; then, with Shack - Hartmann wavefront sensor to detect optical path difference of the GRIN lenses, the aberration of lenses are fully explored. In the manufacture of GRIN lenses, high-power laser beam for curing of polymers at 3-axis mechanical stage is adopted for manufacture of micro optical lens elements. The investigation of the contact performance of photo-curable polymer on silicon substrate is done then the morphology and accuracy of lenses are considered. The goal is to provide a high-efficiency, high-precision, highly flexible lens manufacture method.

M.Ing.
This work comprises the implementation and comparison of five design techniques for the design of gradient-index thin film optical filters: classical rugate, inverse Fourier transform, a wavelet-based design procedure, as well as the flip-flop and the genetic optimization techniques. Designs for a high-reflectance filter, a beamsplitter, a discrete level filter, a distributed filter, and an anti-reflection coating were used to compare the various filter synthesis techniques. The optical thickness of the various examples was maintained below 30 and the refractive index excursion limits were between 1.5 and 3.2. The overall performance of a specific design was evaluated by a weighted merit function. The classical rugate filter uses a sinusoidal refractive index modulation that produces a single reflection band. More complex filters are realized by linear superposition of these elementary profiles. Sidelobe and ripple suppression are obtained by applying quintic windowing functions to the refractive index profile and adding matching layers at the edges of the filter. This filter design procedure has the best figure of merit of 3.73 for the discrete level filter, and the second best of 3.09 for the high-reflectance filter. The inverse Fourier transform links the refractive index profile and reflection spectrum of an optical filter by an approximate relation. It is self-correcting and iterative in nature. It produces filters with the highest optical density. The procedure excels in the design of the distributed filter with a figure of merit of 4.17. Mortlett's wavelet is used as the basis of the wavelet design technique. A single wavelet yields a single reflection band, similar to the classical rugate filter. Sidelobe suppression is an inherent property of the method, but matching layers are needed for passband ripple suppression. The optical density of the high reflection filter is larger for a filter designed with this method than for the equivalent classical rugate filter. The figure of merit of 1.75 for the high-reflectance filter is the best for any of the designs. Flip-flop refinement is a brute force approach to filter design. The layers of a starting design are flipped between two values of refractive index, the change in figure of merit evaluated and the best case saved. This process is repeated for a fixed number of iterations. It is computationally intensive and lacks ripple suppression characteristics. The flip-flop method does not compare well with any of the other techniques. It yields filters with the worst figures of merit for most of the design examples. However, it was applied successfully to the anti-reflection coating. The peak ripple for the anti-reflection filter in the 400 nm to 1100 nm wavelength band is 9.62 % compared to the inverse Fourier transform's 57.30 %. The genetic algorithm operates on the principle of "survival of the fittest". It is a stochastic procedure and yields quasi-random refractive index profiles. It excels with the antireflection coating. The peak ripple in the passband of the anti-reflection coating is 3.29%. The figure of merit for the anti-reflection coating designed with the genetic algorithm is 2.09.

碩士
國立交通大學
光電工程所
89
In order to enhance the functions and compactness of the optical elements for the applications to integrated optics devices, we propose a different type of hybrid optical elements. It is consist of diffractive optical elements and a gradient-index(GRIN) distribution elements1. We have designed several hybrid elements with surface relief diffractive optical elements, such as gratings, a Fresnel lens, and CGH(computer-generation-hologram), and one-dimension GRIN distribution element or a two-dimension GRIN lens. Then we analyze these different hybrid optical elements with rigorous coupled-wave theory, ray-tracing method, and Huygens-Fresnel diffraction theory. Besides, we compare the performance of these hybrid optical elements with those of an individual element and other conventional hybrid optical elements based on simulation results. Moreover, for best performances, we find out the conditions for the optimum optical designs and the practicability to fabricating optical elements. As a conclusion, these hybrid optical elements are functional, compact, and possible to optimize optical design for some applications. In other words, such kind of hybrid elements will be suitable for more applications.

碩士
國立中央大學
光電科學研究所
90
Abstract The gradient-index optical thin film design will become an important topic, since the fabrication of gradient-index optical thin film is easier. Furthermore, among the several methods, only the Fourier transform methods can used as a physical means to explain and understand. Thus it is unnecessary to used try and error or substitution method to derive results, so it is fast and accurate to derive a first step refractive index distribution and correct transmittance spectrum. Then Fourier transforms is used to obtain a result for coupled layer design or modify input transmittance spectrum to get the best design. This thesis has two parts, part one is the use of radio frequency ion beam sputtering and moving target coat composite thin film of refractive index continuously varied from 2.2 to 1.48 and low absorption by Ta and SiO2 targets, to effect the control refractive index to a lower interval of 0.03; Part two is to design optical performance of gradient-index optical thin film by using mathematics formula of Fourier transform to write a computer program. That is transform the transmittance spectrum to a refractive index vs. optical thickness curve by Fourier transform, and finish the first step of an automatic coating control program. To obtain the expected optical performance, the proven moving target method for coating gradient-index optical thin film is practical.

碩士
國立臺灣大學
化學工程學研究所
88
Gradient-index (GI) polymer optical fibers (POF) have attracted extensive interest in light of their versatile applications in optical communication, imaging, and collimating. For fiber fabrication, controlling the proper operation conditions is important to obtain higher quality products and to minimize cost. Theoretical analysis is not only of fundamental interest but also essential for optimizing process conditions. Therefore, this study focus on the theoretical analysis in the fiber fabrication process to find optima conditions and correlate the process parameters and POF properties. Mathematical modeling on the co-extrusion process and centrifugal process for preparing gradient-index GI-POFs were conducted in this study. The theoretical results on these two processes are summarized as below： 1. A theoretical analysis was conducted on a multi-layer internal diffusion and surface evaporation (IDSE) co-extrusion process for preparing gradient-index (GI) polymer optical fibers (POFs). The predicted refractive index distribution (RID) was in good agreement with the experimental data reported in the literature. The effects of the essential parameters, including the mass transfer coefficient of monomer across solid-gas interface k, the diffusivities of monomers, and the radius ratio of each layer, on RID were investigated. 2. Another theoretical analysis was conducted on the preparation of gradient-index (GI) polymeric rods by centrifugal field. Two kinds of materials system were used in this study: polymer/monomer mixture and polymer/dopant mixture. The predicted refractive index distribution (RID) was in good agreement with the experimental data reported in the literature. The effects of the essential parameters, including the molecular weight of the polymer, the composition and component properties (refractive index and density) of the mixture, the rotating speed, and the diameter of the GI rod on RID were investigated.

碩士
國立臺灣大學
化學工程學研究所
89
The polymer optical fiber (POF) has become the main stem of the communicative system due to rapid development in internet. Now there are a lot of literature researching low optical loss, low pulse width, easy coupling graded-index polymer optical fiber. But the most research focus on preparing the closer parabolic-like refractive index distribution (RID) , the POF’s bandwidth of the POF are not analyzied in their studies. The objectives of the thesis are to research the effect of the POF’s bandwidth, including the different process of fabrications of POF, such as the multiplayer coextrusion process, the swollen-gel polymerization process, addition of dopants of BN, BPAc, BSA, BzMA, the different operating wavelength, the source line width, material dispersion, modal disperson. 1.The multilayer coextrusion process: Theoretical analysis was used to simulate the operating performance, by varying the different process parameters, such as open system, close system, the coefficients of mass transfer, the diffusion behavior, initial concentration…etc, the refractive index distribution was obtained. In asymptotic cases, the RID tends to derivate from parabolic. Different RID can effect the modal dispersion and pulse width. If only the effect of modal dispersion is considered, the pulse width will be the lowest when the RID is a perfect parabolic curve. But material dispersion, the difference between the refractive index at the center and periphery of a fiber, operating wavelength, and RID are interrelated must be considered them in order to obtain the optimum RID, since such RID minimized the modal dispersion. And now the material dispersion becomes the most important parameter in controlling the bandwidth of POF. 2.The swollen-gel copolymerization process: By Changing the parameters of the swollen-gel polymerization process, such as the different dopants, the initial concentration of the monomer, the initiator….etc, the refractive index distribution was obtained. The results shows that material dispersion of different dopants is highly dependent on wavelength. Therefore the operating wavelength, material dispersion and the difference between the refractive index at the center and periphery of a fiber must be taken into consideration to obtain which is the important parameter in choosing the doping monomers.