透過您的圖書館登入
IP:44.223.94.103
  • 學位論文

以電漿波導為基礎所發展的多波長與注入放大X光雷射

Development of Multi-Line and Seeded Waveguide-Based Soft X-Ray Lasers

指導教授 : 汪治平 陳賜原 林俊元
若您是本文的作者,可授權文章由華藝線上圖書館中協助推廣。

摘要


雷射的發明已將近半個世紀,這種高同調性光源對於人類的影響可說是無遠弗屆,從光通訊、精密量測、光學儲存與讀寫裝置乃至於醫療美容,無一不深植於現代人類的生活。然而隨著科技的進步,將雷射光推向更短波長的時代已經來臨,如軟X光雷射的發展。軟X光雷射可被應用在半導體製程、材料分析、高密度電漿探測以及高解析度顯微術等多方面,其短波長和符合許多元素共振吸收的特性是可見光雷射所無法取代。在X光雷射的發展上,高發射頻率、高尖峰功率、短脈衝的桌上型雷射系統的發明無疑帶來一股新動力。以短脈衝高功率桌上型雷射搭配光場游離碰撞激發機制,可以產生軟X光波段所需要的雷射增益介質:高游離態電漿,並且可以克服X光輻射生命週期短的問題。這種技術所發展的X光雷射比起同樣產生高同調性X光的同步輻射光和X光自由電子雷射,具有體積小、成本低的優點,是比較符合實際應用上所需求。 本論文的工作首先是協助發展出以全光學式電漿波導為基礎的光場游離碰撞激發的軟X光雷射。利用電漿波導的技術,可以使產生X光雷射增益的紅外光激發雷射克服繞射與游離發散的限制,將操作氣體密度提高一個數量級,並使有效增益長度延伸數倍。因此,我們成功地將32.8奈米類鎳氪離子X光雷射輸出大幅增加四百倍並達到飽和,轉換效率則達到2×10^-6。接著將這種技術推廣到不同的氣體靶材上,用來分別產生41.8奈米類鈀氙離子與46.9奈米類氖氬離子等不同波長的 X 光雷射,甚至還利用氪氣與氬氣混合氣體來製造出雙波長同時輸出的 X 光雷射,使得我們的X光雷射可以在應用上更加豐富多。另一方面,我們透過研究X光雷射輸出對不同控制參數的變化,藉此深入了解此種X光雷射的特性,進而掌握對它的控制調變能力。在成功地提高X光雷射輸出後,我們希望進一步提升X光雷射的光學品質。所以我們利用一道線偏振短脈衝雷射光游離氬原子外層電子,電子在線性震盪電場作用下回撞原本離子,與之結合並釋放出位於X光波段的高階諧波,其為具有良好時空波形的短脈衝,特別適合做為X光雷射放大器的種子脈衝。之後經由時間、空間和頻譜上精密的微調,將高階諧波注入到以電漿波導為基礎的X光雷射放大器來放大。透過這種注入放大的機制,我們成功地產生高同調性、小發散角以及具有線偏振性質的X光雷射。我們相信透過高階諧波、電漿波導與光場游離碰撞激發機制這三種方式的結合,可以提供未來產生短脈衝、高強度、高光學品質X光雷射的一個重要參考原型。

並列摘要


It has been nearly half a century since the invention of lasers, the use of coherent light has become an indispensable part of our world, such as optical communications, precision measurements, optical memories, and medicine. Rapid progress in technology has led to the development of coherent lights that operate in short-wavelength regions, examples of such light sources include soft x-ray lasers. The use of soft x-ray lasers has considerable potential from the viewpoint of pioneering research in various scientific fields like high-resolution microscopy and holography, dense plasma measurement, and nano-lithography; visible lasers are inadequate for these purposes. With the advent of high-power short-pulse lasers, especially the high-repetition-rate terawatt lasers based on the chirped-pulse amplification technique, it is now possible to generate ultrashort coherent soft x-rays with a much lower cost and small size. An ultrashort high-intensity laser pulse combined with the optical-field-ionization (OFI) collisional-excitation mechanism can be used to produce a suitable x-ray gain medium: highly ionized plasma. In addition, the ultrashort feature of the pumping source can overcome the problem of the short duration of the gain in the x-ray region. Considering the size and cost, the use of a table-top, high brightness, soft x-ray laser is advantageous as compared to synchrotron radiations or x-ray free electron lasers. This thesis first reports the development of an OFI collisional-excitation soft x-ray laser that uses an optically preformed plasma waveguide. Using a 9-mm-long pure krypton plasma waveguide prepared by the axicon ignitor-heater scheme, Ni-like Kr lasing at a wavelength of 32.8 nm can be enhanced by 400 times relative to the case without the plasma waveguide. An output level of 8×10^10 photons/pulse can be obtained at an energy conversion efficiency of 2×10^6. Then, under the same configuration of the pump and waveguide-forming pulses, strong Pd-like xenon lasing and Ne-like argon lasing were realized at wavelengths of 41.8 nm and 46.9 nm, respectively. In addition to the main lasing lines for Ni-like krypton and Ne-like argon, other lasing lines are also observed; this is indicative of a strong enhancement effect and a large gas density in the plasma waveguide. With a Kr/Ar mixed gas multi-species parallel x-ray lasing was also demonstrated, showing the capability of generating multi-line soft x-ray lasers by using the optically preformed plasma waveguide. In order to gain a better understanding of waveguide-based soft x-ray lasers and control them suitably, extensive experimental results on the pump-energy dependence, density dependence, and effects of parameters that control the waveguide fabrication were studied in detail. Finally, in order to realize further improvements in the optical qualities of the soft x-ray laser, a strongly saturated waveguide-based OFI soft-x-ray laser seeded by high harmonic generation (HHG) was demonstrated for Ni-like Kr lasing at a wavelength of 32.8 nm. HHG is produced from the nonlinear interaction between intense laser and gas atoms. During this process, electrons that are ionized from the gas atoms oscillate with the laser field; subsequently, they recombine with their parent ions and emit high-energy photons. The emissions from di®erent atoms add constructively and thus retain good spatial and temporal coherence. As compared to laser seeded with only spontaneous emission, the divergence of seeding with HHG is greatly reduced from 4.5 mrad to 1.1 mrad, which is about the same as that of the HHG seed. The amplified HHG seed pulse also shows enhanced spatial coherence and controlled polarization. Moreover, seeded x-ray lasers do not suffer from timing jitter relative to the pump laser; this is important for pump-probe applications. We believe that the integration of high-harmonic seeding, optically preformed plasma waveguide, and OFI pumping forms one of the optimal archetype of a high-repetition-rate, high-intensity, ultrashort-pulse soft x-ray laser.

參考文獻


[43] S. Sebban, R. Haroutunian, P. Balcou, G. Grillon, A. Rousse, S. Kazamias, T. Marin, J. P. Rousseau, L. Notebaert, M. Pittman, J. P. Chambaret, A. Antonetti, D. Hulin, D. Ros, A. Klisnick, A. Carillon, P. Jaegle, G. Jamelot, and J. F. Wyart, Saturated amplification of a collisionally pumped optical-field-ionization soft x-ray laser at 41.8 nm," Phys. Rev. Lett. 86, 3004-3007 (2001).
[82] P. Zeitoun, G. Faivre, S. Sebban, T. Mocek, A. Hallou, M. Fajardo, D. Aubert, P. Balcou, F. Burgy, D. Douillet, S. Kazamias, G. de Lacheze-Murel, T. Lefrou, S. le Pape, P. Mercere, H. Merdji, A. S. Morlens, J. P. Rousseau, and C. Valentin1, A high-intensity highly coherent soft x-ray femtosecond laser seeded by a high harmonic beam, Nature 431, 426-429 (2004).
[96] T. Mocek, S. Sebban, G. Maynard, P. Zeitoun, G. Faivre, A. Hallou, M. Fajardo, S. Kazamias, B. Cros, D. Aubert, G. de Lacheze-Murel, J. P. Rousseau, and J. Dubau, Absolute time-resolved x-ray laser gain measurement, Phys. Rev. Lett. 95, 173902 (2005).
[121] S. Sebban, T. Mocek, D. Ros, L. Upcraft, P. Balcou, R. Haroutunian, G. Grillon, B. Rus, A. Klisnick, A. Carillon, G. Jamelot, C. Valentin, A. Rousse, J. P. Rousseau, L. Notebaert, M. Pittman, and D. Hulin, Demonstration of a Ni-like Kr optical-field-ionization collisional soft x-ray laser at 32.8 nm, Phys. Rev. Lett. 89, 253901 (2002).
[38] D. V. Korobkin, C. H. Nam, and S. Suckewer, Demonstration of soft

延伸閱讀