Study of Ce3+:YAG crystal fiber based polarization sensitive optical coherence tomography

超高縱向解析度光學同調斷層掃描術是該領域發展的趨勢，而縱向解析度與光源頻寬有關，且光源頻寬越寬，其縱向解析度越好，因而能觀察到待測樣品更細微的結構。另一方面，功能型光學同調斷層掃描術則可提供額外影像資訊與增加影像對比。其中，極化靈敏光學同調斷層掃描術，可以量測出待測樣品極化相關之物理量。此外，選擇近高斯光譜光源與低光譜雜訊，能降低邊陲雜訊 (side-lobe noise) 的影響，進而減少縱向畫素串音(image pixel crosstalk)問題，增進影像品質。在此，增益自發輻射(amplified spontaneous emission, ASE)光源符合上述之要求，可產生近高斯光譜與寬頻光源。藉由光波導結構收集增益自發輻射光，則能有效提升系統光源光功率，進而增加穿透深度以及訊雜比。 本實驗室利用摻鈰釔鋁石榴石作為光源的生長材料，藉由共抽拉雷射加熱長晶法，能夠長出直徑10微米以下之小纖心雙披覆晶體光纖(double-clad crystal fiber, DCF)，並同時擁有1.5微米縱向解析度之寬頻光源。論文中，我們架設出極化靈敏光學同調斷層系統，並應用在具有雙折射特性的鐵電晶體與液晶測試片。在鐵電晶體的觀測上，估計出共融配比鈮酸鋰鐵電域之+z與-z間的折射率差為4.22×10-4，並推出其色散曲線，同時也非破壞性地量測晶體蝕刻後的表面形貌。另外，在外加偏壓的方式偏壓於水平配向液晶面板，藉由將液晶層分成兩層，進一步利用此系統觀察相位延遲的二維影像分佈，並估算出液晶的有效傾角從5.57度變化到66.89度。就我們所知，這是第一次量測出有效傾角隨深度變化的資訊。Urta-high axial resolution is a tendency toward development of Optical Coherence Tomography (OCT). The axial resolution depends on the bandwidth of the light source. The more broad band it is, the better axial resolution is. Thus finer structure of under-test sample can be found out. On the other hand, functional OCT can offer extra information and contrast of picture. Polarization sensitive Optical Coherence Tomography(PS-OCT) could measure the physical property related to polarization of under-test sample. Besides, near-Gaussian spectrum source and lower spectrum noise are the better choice in order to reduce the side-lobe noise, which decreases the problems of image pixel crosstalk and improves the quality of picture. Furthermore, the light source of amplified spontaneous emission (ASE) meets above requirements, which generates near-Gaussian spectrum and broad band light source. It is a better way to push up the system power by using waveguide to collect the ASE light and results in a high depth of penetration and better signal-to-noise ratio. Our laboratory used the Ce3+:YAG as the material of source rod. The co-drawing laser-heated pedestal growth method is adopted to grows the double-clad crystal fiber(DCF) with a diameter less than 10 μm, which has 1.5-μm axial resolution in air. In this thesis, we successfully set up an OCT system and applied to the area of birefringence ferroelectrics and liquid crystal test sample. As for the former observation, we estimated Refractive Index of congruent lithium niobate between +z and –z domain is 4.22×10-4 and speculated its dispersion curve. At the same time we measured the crystal surface profile after etching process by non-destructive test.Furthermore, increasing applied voltage on the horizontal plane of liquid crystal panel. To separate liquid crystal into two layers, we can observe more about phase retardation and two-dimensional distribution. Also the serious variation of effective tilt angle from 5.57 to 66.89 degree is to be estimated. As we know, this information that the depth dependence of effective tilt angle can be measured effectively is first time to be released