<p> A laser diode emits a narrow range of frequencies. However, drifts in frequency occur over time due to many factors like changes in laser temperature, current, mechanical vibrations in the apparatus, etc. These frequency drifts make the laser unsuitable for experiments that require high frequency stability. We have used an atomic transition in rubidium as a frequency reference and used Doppler free saturated spectroscopy to observe the reference peak. We have designed an electronic locking circuit that operates the diode laser at a specific frequency. It keeps the laser at that frequency for a long period of time with very few or no drifts. </p><p> We have constructed and characterized an extended cavity diode laser that costs significantly less than a commercial unit. It is much more compact with performance comparable to that of a commercial unit. It can be used in undergraduate and graduate optics laboratories where commercial units are cost prohibitive. The various components of the set-up are discussed, and the basic principles behind the function and operation of this versatile device are explained. We designed a servo loop filter circuit, which is used to stabilize the frequency of the laser to an atomic reference frequency. We also generated an error signal using a technique similar to the Pound Hall Drever technique and then feedback the error signal in the loop filter circuit. </p>

<p> This thesis contains a discussion of the theoretical background for Fourier spatial filtering and a description of the design and construction of a portable in-class spatial filtering apparatus. A portable, in-class spatial filtering demonstration apparatus was designed and built. This apparatus uses liquid crystal display (LCD) panels from two projectors as the object and filter masks. The blue LCD panel from the first projector serves as the object mask, and the red panel from the second projector serves as the filter mask. The panels were extracted from their projectors and mounted onto aluminum blocks which are held in place by optical component mounts. Images are written to the LCD panels via custom open source software developed for this apparatus which writes independent monochromatic images to the video signal. The software has two monochromatic image windows, basic image manipulation tools, and two video feed input display windows. Two complementary metal-oxide semiconductor (CMOS) sensors are positioned to record the reconstructed image of the object mask and the diffraction pattern created by the object mask. The object and filter mask can be digitally changed and the effects on the filtered image and diffraction pattern can be observed in real-time. The entire apparatus is assembled onto a rolling cart which allows it to be easily taken into classrooms. </p>

<p> Precise characterization of waveguide parameters is necessary for the successful design of nonlinear photonic devices. This dissertation contains a description of methods for the experimental characterization of distributed Bragg reflectors for use in nonlinear optics and other applications. The general coupled-mode theory of Bragg reflection arising from a periodic dielectric perturbation is developed from Maxwell's equations. This theory is then applied to develop a method of characterizing the fundamental parameters that describe Bragg reflection by comparing the spectral response of Bragg reflector resonators. This method is also extended to characterize linear loss in waveguides. A model of nonlinear effects in Bragg reflector resonators manifesting in bistability is also developed, as this phenomenon can be detrimental to the characterization method. Specific recommendations are made regarding waveguide fabrication and experimental design to reduce sources of experimental error.</p>

<p> We have developed a one dimensional numeric simulation of the amplification of broadband laser light in a chirped pulse amplification (CPA) system containing an amplifier with a broadband gain spectrum. We present the theory concerning the generation of laser pulses and pulse shape altering effects. We model the amplification of monochromatic light in a narrow bandwidth amplifier as demonstrated by Lee M. Frantz and John S. Nodvik in their 1963 paper. Using the CPA method, we expand this model to describe the amplification of broadband laser pulses by an amplifier with a broadband gain profile. This model represents systems that are dominated by inhomogeneous broadening, as well as homogeneous broadening effects. Our model also addresses the effects of gain saturation within the amplifier. We present the theory supporting this model and discuss its implementation in a LabView hosted environment. We then present results modeled for several systems.</p>

<p>In this dissertation, experimentally measured spectral and coherence evolution of supercontinuum (SC) is presented. Highly nonlinear soft-glass photonic crystal fibers (PCF) were used for SC generation, including lead-silicate (Schott SF6) PCFs of a few different lengths: 10.5 cm, 4.7 mm, and 3.9 mm, and a tellurite PCF of 2.7 cm. The pump is an optical parametric oscillator (OPO) at 1550 nm with pulse energy in the order of nanojoule (nJ) and pulse duration of 105 femtosecond (fs). The coherence of SC was measured using the delayed-pulse method, where the interferometric signal was sent into an optical spectrum analyzer (OSA) and spectral fringes were recorded. By tuning the pump power, power-dependent evolution of spectrum and coherence was obtained. Numerical simulations based on the generalized nonlinear Schrodinger equation (GNLSE) were performed. To match the measured data, the simulated spectral evolution was optimized by iteratively tuning parameters and comparing features. To further match the simulated coherence evolution with the measurement, shot noise and pulse-to-pulse power fluctuation were added in the pump, and the standard deviation of the fluctuation was tuned. Good agreement was obtained between the simulated and the measured spectral evolution, in spite of the unavailability of some physical parameters for simulation. It is demonstrated in principle that, given a measured spectral evolution, the fiber length, and the average power of SC, all other parameters can be determined unambiguously, and the spectral evolution can be reproduced in the simulations. Most importantly, the soliton fission length can be simulated accurately. The spectral evolution using the 4.7- and the 3.9-mm SF6 PCFs shows a pattern dominated by self phase modulation (SPM). This indicates that, these fiber lengths are close to the soliton fission length at the maximum power. The spectral evolution using the 10.5-cm SF6 PCF and the 2.7-cm tellurite PCF shows a soliton-fission-dominated pattern, indicating these lengths are much longer than the soliton fission length at the maximum power. For the coherence evolution using the SF6 PCFs, the simulations and the measurements show qualitative agreement, confirming the association between coherence degradation and soliton fission. For the case of the tellurite PCF, nearly quantitative agreement is shown, and it is shown that the solitonic coherence degrades slower than the overall coherence. Fluctuation of coherence occurs at the regime where the coherence starts to degrade, in the measurement and the simulations of the SF6-PCF case. It is shown that the cause is the pulse-to-pulse power fluctuation in the pump. The pulse-to-pulse stability of spectral intensity is another characterization of SC stability, other than the coherence. It is shown by simulations that these two exhibit different dynamics, and have low correlation.

A practical geometric optics method for derivation of the optical forces from light rays was described. By this method, the forces from a G.P.W. (Gaussian Plane Wave) and a general TEM$ sb infty$ laser beam were calculated and studied. For a G.P.W. beam, there were two forces which acted on small particles located inside the electromagnetic field; one, called the scattering force, directed in the beam propagation direction, pushed particles axially. The other, called the gradient force, due to the non-uniformity of the electromagnetic field, acted like an optical well and confined the particles of the beam axis. The forces from a general TEM$ sb infty$ beam behaved differently due to the profile of the beam. It was shown that axial confinement was also possible for a highly focused TEM$ sb infty$ beam, therefore providing the possibility of single beam trapping. The relationship between the forces and the profile of a TEM$ sb infty$ laser beam was investigated comprehensively. / Three experimental stations were designed and built. Both upward and downward accelerating experiments were constructed to confirm the existences of the scattering force and the gradient force in a G.P.W. beam. Furthermore, the scattering force was studied quantitatively. A single beam trapping experiment was designed to verify the possibility of axial constraint of small particles by a higher focused TEM$ sb infty$ laser beam. The single beam trapping conditions found in the experiment were in agreement with the results of the theoretical analysis.

An emission spectroscopy study was performed on a magnetically rotated electric arc between two concentric copper electrodes. Two methods were proposed to analyse the recordings of the line intensities as the arc column passed in front of the optical system. / The averaging of a series of intensity profiles was the first method. Consistancy between the average value of some parameters applied to these profiles and the value of these parameters on the average quantity was checked. Volumetric emissivity profiles were then obtained. / The second method consisted of electronic integration of line intensities during several arc passings. The proportionality between this average intensity and the maximum emissivity in the arc column was checked. / These two methods were used to determine the copper vapour density and the arc temperature as a function of two contaminants in the main argon flux: carbon monoxyde and nitrogen. The temperature was slightly superior to 7500 K in the first case and slightly inferior in the second. Maximum copper vapour density found was 5 10$ sp{21}$ m$ sp{-3}$ in argon contaminated with carbon monoxide. It was probably higher than 10$ sp{22}$ m$ sp{-3}$ in Argon contaminated with nitrogen.

Bifurcations and complex oscillations in the human pupil light reflex (PLR) are studied. Autonomous pupil area oscillations are produced by substituting electronically controllable nonlinear feedback for the normal negative feedback of this reflex. A physiologically sound theoretical framework in which to study pupillary oscillations is developed. The model, framed as a delay-differential equation (DDE), agrees quantitatively with the simpler periodic behaviors and qualitatively with the complex behaviors. Much of the aperiodicity in the data can be ascribed to noise and transients rather than to chaos. The critical behavior of the PLR at oscillation onset is different with piecewise constant rather than smooth negative feedback. In the former, relative fluctuations in period are larger than those in amplitude, and vice versa in the latter. Properties of the time solutions and densities of a stochastic DDE are used to explain this experimental result. The Hopf bifurcation in this system is postponed by both additive and multiplicative colored noise. Theoretical insight into the behavior of stationary densities of DDE's and the origin of the postponement is given, and implications for analyzing bifurcations in neural delayed feedback systems are discussed.

Ultra-small angle light scattering (USALS) is a technique used to probe large average spatial and temporal structure of soft condensed matter complementary to microscopy. Limited information is available on the design and features of a multi-speckle CCD-based USALS apparatus. The optics of such a setup are described followed by an optimization scheme involving ray tracing that can be used to choose the optimum lenses by taking into account the finite spot size due to lens aberrations, diffraction, and the CCD pixel size. Results of calculations of the optimization scheme are presented for a static light scattering (SLS) setup followed by a few experimental tests of our current apparatus.

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2007. / Source: Dissertation Abstracts International, Volume: 68-11, Section: B, page: 7406. Adviser: Paul Kwiat. Includes bibliographical references (leaves 62-66) Available on microfilm from Pro Quest Information and Learning.