Advances in integrated photonic devices require low loss, easy-to-integrate solutions for chip-to-chip and chip-to-fiber interfacing. Among the most common solutions are traditional lenses. However, circular lenses require additional mounting mechanisms to ensure proper alignment. Additionally, the beam routing functionality cannot be added to the traditional lenses unless they are combined with mirrors and operate in the reflection mode. In this dissertation, we investigate lens-embedded photonic crystals (LEPCs) as a solution to flat and multifunctional lenses. The concept is demonstrated by creating self-collimating lattices containing a gradient refractive index lens (GRIN-LEPC), a binary-shaped lens (B-LEPC), and a Fresnel-type binary-shaped lens (F-B-LEPC). The devices are fabricated in a photopolymer by multi-photon lithography with the lattice spacing chosen for operation around the telecom wavelength of 1550 nm. Both the experimentally observed optical behaviors and simulations show that the device behaves like a thin lens, even though the device is considerably thick. The thickness of a B-LEPC was reduced threefold by wrapping phase in the style of a Fresnel lens. Embedding a faster-varying phase profile enables tighter focusing, and NA = 0.59 was demonstrated experimentally. Furthermore, we demonstrate experimentally that a Fresnel lens can also be combined into a bender, so one PC performs both bending and focusing functions, further reducing the footprint of the PC devices. We also explored a hexagonal lattice and demonstrated wide-angle and broad-band self-collimation. The PCs are fabricated using the same material and method as that of the LEPCs. Optical characterization shows that the device strongly self-collimates light at near-infrared wavelengths that span from 1360 nm to 1610 nm. Self-collimation forces light to flow along the extrusion-direction of the lattice without diffractive spreading, even when light couples into the device at high oblique angles. Numerical simulations corroborate the experimental findings.
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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 (Open Access)
Xia, Chun, "Light Guiding and Concentrating using Self-Collimating Spatially-Variant Photonic Crystals" (2022). Electronic Theses and Dissertations, 2020-. 1700.