This dissertation consists of two main sections. The first is a review of laser resonators using spherical mirrors, and incorporates a physical optics numerical model of a Fabry-Perot laser resonator without gain. The output of this model, which includes spot sizes, loss, and transverse mode formation, is compared to the parameters calculated using published analytical results. This comparison serves as a verification of the numerical methods used, as well as a frame of reference for the model of a Porro prism resonator which follows in the second section. The second section proposes a new method for analysing Porro prism resonators. The analysis incorporates both geometric as well as physical optics concepts, with the prisms modelled as rotating elements with amplitude and phase distortions. This yields expressions for the orientation of the loss at the apex of each prism, and as well as the number of petals in the “petal-pattern” beam structure commonly observed from Porro prism lasers. These expressions are included in a numerical model, which is first used to verify the development of the characteristic petal-pattern. Next, the numerical model is used to investigate the development of the beam structure, in both time and space, in crossed Porro resonators with a range of Fresnel numbers and stability parameters. This leads to some new insight into the transverse modes of these lasers. / Thesis (M.Sc.)-University of KwaZulu Natal, Westville, 2008.

Pu Xiao-Yun. / "December 2000." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2000. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

Introduction: For approximately the last eight years the Laser Section of the National Physical Research Laboratory (NPRL) has been interested in inter alia, pulsed solid-state lasers and in particular, Nd:YAG. Investigations of various resonator types were undertaken with a view to the improvement of the laser parameters such as output energy, pulse width, beam quality and sensitivity to mirror misalignment. In 1980 a Nd: YAG laser employing a rotating prism Q-switch was constructed (Preussler (1980)). It involves rotating one of the two cavity reflectors so that they are parallel for only a brief instant in time. Typically the prism must rotate at a speed of 20 000 r.p.m. to ensure a single pulse output. Such lasers suffer from the tendency to emit multiple pulses, they are very noisy and they require frequent maintenance because of the short lifetime of the bearings. A resonator employing conventional curved mirrors and an electro-optical Q-switch was constructed in 1980 (Robertson & Preussler (1982)). In 1981 an electro-optically Q-swi tched laser making use of a crossed Porro-prism resonator was investigated due to its relative insensitivity to misalignment of the reflectors compared with the conventional mirror resonator (Nortier (1981)). Improvements in terms of output power, beam divergence and beam quality can be achieved by making use of a so-called unstable resonator. Such a laser has been investigated and is reported on in this study. Chapter 2 provides some background into laser theory and operation while chapter 3 deals with the theory of the unstable resonator. Chapter 4 provides details of the experimental equipment and techniques used in the work and chapter 5 discusses the evaluation of the project and results obtained.

A reflective Tiered Fresnel Zone Plate, herein called a Tiered Fresnel Mirror TFM, with a focal length on the order of a meter is studied for use as the mirror(s) in a Fabry-Perot interferometer type of laser. The relative phase transition within the individual zones (ideally smooth from zero to pi ) is stair-stepped or tiered in the longitudinal direction of the mirror. Within an individual zone the step height is constrained to a constant whereas the width of the tiers are monotonically decreased when traversing radially outward so that the overall profile follows the ideal smooth curve. The effectiveness of the number of tiers per zone, measured by the loss per pass or round-trip, varies from a Plane Mirror (zero tiers per zone) to a Spherical Mirror (an infinite number of zones per tier). The Fox and Li iterative method of determining the E-Field as the beam propagates back and forth is applied to an empty cavity resonator to determine the diffraction loss. A computer program is written to investigate the diffraction loss of various mirror configurations. The performance of the TFM is found to be not as efficient as the Spherical Mirror (the number of tiers per zone is shown to be a major variable) but may be tolerable under applications of a moderately high gain laser medium. The Gaussian Fundamental mode is easier to maintain since the higher order modes have a higher loss per round trip. The manufacture of the TFM can be incorporated easily into an IC process thereby making the cost of the novel mirror relatively cheap when produced in quantities. A major cost variable is again the number of tiers per zone which is proportional to the number of processing steps. The TFM's performance with respect to the etch depth of the steps in the mirror's stair-stepped profile is simulated and found to be a very doable etch with the current plasma etch technology.

Thesis (PhD)--Stellenbosch University, 2015.

This thesis describes a number of studies of microstructured optical resonators, designed with the aim of enhancing the performance of organic semiconductor lasers and exploring potential applications. The methodology involves the micro-engineering of the photonic environment in order to modify the pathways of the emitted light and control the feedback mechanism. The research focuses on designing new organic microstructures using established semi-analytical and numerical methods, developing fabrication techniques using electron-beam lithography, and optically characterising the resulting structures. Control of the feedback mechanism in conjugated polymer lasers is first investigated by studying Distributed Feedback or photonic crystal resonators based on a square feedback lattice. This study identified the diffraction to free space radiation as a major source of loss in current microstructured resonator designs. By cancelling the coupling to free space through the use of different feedback symmetries and diffraction orders, a threshold reduction by almost an order of magnitude is demonstrated. The introduction of mid-gap defect photonic states in an otherwise uniformly periodic structure was studied in Distributed Bragg Reflector (DBR) resonators. This enabled GaN diode pumped polymer lasers to be demonstrated, indicating that the transition from complex excitation sources to more compact systems is possible. Devices for potential applications in the field of optical communications are also explored by demonstrating a polymer DBR laser based on silicon. In this way, the potential for integrating conjugated polymers with silicon photonics is confirmed. Photonic crystal fibres, which have a periodic microstructure in the transverse direction, are explored as an alternative means for controlling the optical properties of organic lasers. Fluidic fibre organic lasers were demonstrated as efficient sources with good spectral purity. In these devices, mechanisms to tune the emission wavelength were explored and the origin of the frequency selection mechanism was investigated.