Functional Optical Coherence Tomography Based on Broadband Crystal Fiber Light Source
Date Issued
2015
Date
2015
Author(s)
Ho, Tuan-Shu
Abstract
With the co-drawing laser-heated pedestal growth (CD-LHPG) method, various crystal fibers were developed. Ce:YAG, Ce:YSO, and Ti:sapphire crystal fibers grown in our laboratory generate broadband, continuous-wave, and near-Gaussin florescence spectra under laser diode pumping, and are suitable to be the light source of optical coherence tomography (OCT) system. The Ce:YSO crystal fiber light source has a broadband fluorescence emission in the blue wavelength range, and the OCT system based on the Ce:YSO light source can achieve a 0.6-μm axial resolution on single cell measurement, and 0.5-μm axial resolution on examination of panel devices. The crystal fiber light source has high brightness, large numerical aperture and multi-transverse-mode, and the design rules for crystal-fiber-based OCT are much different from the commercial OCT systems with tunable lasers or pig-tailed superluminescent diodes (SLD) as light sources. In this dissertation, the issues related to the fabrication of spectral-domain and full-field OCT systems are also presented and discussed. The crystal-fiber-based OCT systems are not only capable for high-resolution structural imaging, but also suitable for functional analysis. The broadband property of crystal fiber light sources also provides a large available bandwidth for spectroscopic analysis. Their near-Gaussian lineshapes also help to reduce the crosstalk problem for time-frequency analysis. A series of OCT systems are were implemented for the study of various corneal properties, and the performances were tested with human eye models. The OCT tonometry system in our laboratory, can achieve high speed intraocular pressure measurement, and to provide information related to the corneal elasticity. With carrier-analysis-based algorithm, a full-field OCT keratometry and achieve two-dimensional curvature mapping within 6-mm diameter within 70 milliseconds. An OCT approach for characterization of absorptive thin-film materials was developed, which can obtain the thickness and optical properties of absorptive films with micrometer thickness. With the Ce:YAG and Ce:YSO crystal fiber light source, the systems are able to measure the refractive index and extinction coefficient spectra from 400 to 600 nm, and a 0.15% precision was achieved on the film thickness measurement on various absorptive films.
Subjects
optics
light source
crystal
fiber
optical coherence tomography
material characterization
Type
thesis
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