極紫外光數位全像顯微術

Abstract

高亮度短波長同調光源因其於基礎研究與工業應用逐漸增長的需求潛力而亟待 發展。隨著植基於啾頻脈衝放大技術所發展之強場雷射的誕生，以更低廉的價格 與更小巧的體積產生超短同調極紫外脈衝輻射不再只是個夢想。在第一章及第二 章，我們紀錄了實驗室近年在波長為32.8 奈米極紫外光雷射的發展現況，汲發 能量小於1 焦耳的條件下每發雷射即可產生10^12 顆光子，達到空前的10^-5 高能量 轉換效率。 第三章至第五章聚焦在以 32.8 奈米波長極紫外光雷射為照射光源的一種新發 展無孿生像數位全像顯微術。其計算核心 -「單全像互投影演算法」經數值模擬 和光學實驗證明其確能有效抑制傳統全像重建術所會遭遇的相位混淆，進而回解 可得無孿生像干擾的高解析物體影像。相較於傳統方法，「單全像互投影演算法」 全然免除為了攫取正確物體相位所需物體輪廓的預知條件，使這新穎的演算法更 加適合應用在需要大量計算量的三維體積成像。

Bright short-wavelength coherent light sources owe their existence to the growing potential demand in both fundamental researches and industrial applications. With the advent of high-field lasers based on the chirped-pulse amplification technique, generating ultrashort coherent extreme-ultraviolet radiations with a much lower cost and even smaller size is no longer pie in the sky. In Chapter 1 and Chapter 2, we report the recent development of the extreme-ultraviolet laser at 32.8 nm in our laboratory. An average output of 10^12 photons per pulse is obtained at a pump energy of less than 1 joule, reaching an unprecedentedly high energy conversion efficiency of around 10^−5. Chapter 3 to Chapter 5 focus on a newly developed twin-free digital holographic microscopy using a 32.8-nm extreme-ultraviolet laser as the source of illumination. The computational core, single-hologram inter-projections algorithm, is numerically and experimentally proved to be capable of effectively depressing the phase ambiguity that is always encountered in the conventional reconstruction method, leading to high-fidelity object images without annoying twin disturbances. Full exemption from seeking a tight support constraint for retrieving the correct object phase also makes single-hologram inter-projections reconstruction method more fit for volumetric imaging that intrinsically requires a great amount of computational effort.