Bragg diffraction is a natural phenomenon that arises from the coherent interference of scattered waves in multilayer structures with a well-defined periodicity. In practice, the physical size of these multilayer structures varies depending on the intended application, from micrometer-thick dielectric mirrors with tens of layers to centimeter-long Bragg gratings with ten-thousands of layers. The scope of this work centers around a unique class of multilayer elements developed in bulk photo-thermo-refractive (PTR) glass – the volume Bragg grating (VBG). The content of this thesis places an emphasis on the volume nature of these Bragg devices, implying a three-dimensional structure whereupon arbitrary spatial phase information can be embedded for laser-beam shaping, or the distribution of Bragg periods across each element is instead engineered to yield diffracted light with distinct spatio-temporal properties. In Chapter 1, operating principles, and fabrication technique of a conventional VBG are introduced. Owning to the principles of Bragg diffraction, the desired spatial and/or spectral phase information can be encoded onto the interference of scattered waves, reflecting from different sections along a grating volume. In Chapter 2, this principle is implemented in the form of phase-shifted volume Bragg gratings, whereby desired phase information is holographically engineered into the relative shift between neighboring Bragg substructures. Unlike other known active or passive phase-shaping tools, these phase-shifted elements can reconstruct the encoded phase profiles over a broad range of wavelengths that meet the Bragg condition of the VBG. On the other hand, the chirped volume Bragg grating, identified by a unique variation in grating periods across its volume, presents an alternative mean upon which phase information can be encoded – i.e., the Bragg-period distribution. Gratings of this kind are addressed in detail through Chapter 3. Due to the adaptability of holographic technique employed for the fabrication of volume gratings, a new class of Bragg elements is explored, capable of inscribing phase information into both (1) the relative shift among local Bragg elements, and (2) the Bragg-period variation across the grating volume. Chapter 4 reports on the construction of these hybrid structures, referred to as the phase-shifted, chirped volume Bragg gratings. Their unique ability to double as distributed feedback lasers, when recorded into the optically active volume of doped PTR glass, is discussed, paving the way for a novel source of light – the chirped, distributed feedback laser.
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Doctor of Philosophy (Ph.D.)
College of Optics and Photonics
Optics and Photonics
Optics and Photonics
Length of Campus-only Access
Doctoral Dissertation (Campus-only Access)
Mach, Lam, "Volume Bragg Gratings With Complex Phase Structures: A Three-Dimensional Foundation For Laser-Beam Engineering" (2022). Electronic Theses and Dissertations, 2020-. 1611.
Restricted to the UCF community until February 2024; it will then be open access.