High Resolution Cr4+:YAG Based Optical Coherence Tomography System
Date Issued
2010
Date
2010
Author(s)
Hsu, Po-Kai
Abstract
For optical coherence tomography (OCT), axial resolution is determined by center wavelength and bandwidth of the light source, whereas signal-to-noise ratio (SNR) is affected by instability of the light source. The Cr4+:YAG double-clad fiber made by our own is not only broadband in spectrum but also highly stable; therefore, it is certainly suitable for the development of high axial resolution and high SNR near infrared OCT scanning systems.
By means of laser heated pedestal growth (LHPG) method, we have successfully fabricated a Cr4+:YAG double-clad fiber, generating broadband amplified spontaneous emission (ASE) centered at 1.40 μm with a bandwidth of 233 nm, a variance 2.4*10^-8 W of power and 0.24% instability by an 1064-nm Yb:fiber laser pump. Using the ASE as light source of the OCT system, we have shown a 26.5 dB 1st cross talk factor and 37.1 dB 2nd cross talk factor of axial image cross talk, we also have 3.7 μm axial resolution, 18 μm transversal resolution and 76-dB SNR.
We successfully built up a 3D OCT system by a Cr4+:YAG double-clad fiber, axial and transversal stepping motor and a scanning mirror. We scanned and analyzed the inductor part of IC as a non-biological sample and found out the thickness of metal layer is 1.4 μm and the optical path length of substrate is 6.8 μm which matches the design of IC. On the other hand, we scanned biological samples and demonstrated a result of 7.4-μm-thick single-layer human pulmonary adenocarcinoma cells, we also demonstrated the moisture difference in skin with ASE spectrum deformation caused by the water absorption.
Subjects
optical coherence tomography
Cr4+:YAG double-clad fiber
broadband light source
crystal fiber
3D scan
moisture analysis
Type
thesis
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