脈衝塑型器輔助之超快任意光波形量測與組合

Shaper-assisted ultrafast optical arbitrary waveform characterization and synthesis

陳季丞(Cheng, Chen Chi)

指導教授 ： 楊尚達

國立清華大學/電機資訊學院/光電工程研究所/博士(2014年)

https://doi.org/10.6843/NTHU.2014.00166

摘要

任意光波形可藉由對脈衝光譜的每一根譜線做獨立之振幅、相位之調變而達成，此一技術可在時域上實現100%工作週期之光脈衝序列。若更進一步對脈衝的兩個正交電場成分做獨立之振幅、相位調變，則可以將純量場任意光波形推廣至具有時變極化態之向量場任意光波形。除了達成理論上光場複雜度的極限，這類光場可用於具飛秒級時間解析度及奈米級空間解析度之電漿子元件選擇性激發。 傳統上純量場或向量場超短脈衝的量測可藉由產生ㄧ對孤立的相同脈衝做時間取樣或頻譜干涉。然而工作週期達100%之任意光波形無法在時域上完全分離，增加了量測的困難。已發展的量測技術需使用轉換極限脈衝或同步射頻訊號等參考訊號來輔助量測。然而轉換極限脈衝取得不易，且量測超高重複率脈衝序列(如重複率為1011赫茲之刻爾光頻梳)時，射頻訊號會有頻寬不足的問題。 本論文致力於使用全光學技術，在不需冗長的迭代演算法與高速電子元件之下量測及合成任意光波型。所發展之脈衝塑型器輔助量測系統容易精確校正系統參數、具有極佳的量測準確度、且將量測及合成整合為單一系統。實驗架構適用於極限紫外光波段，並可應用於量測超高重複率脈衝序列。

關鍵字

超短脈衝量測 ； 全向量光場量測 ； 脈衝塑型

並列摘要

Integration of optical frequency comb and spectral line-by-line pulse shaping can generate optical arbitrary waveform (OAW) with ultrafast evolution of amplitude and phase spanning up to the entire repetition period (100% duty cycle). By independently controlling the electric fields at two orthogonal polarizations, one could generalize the OAW to vectorial OAW (V-OAW) with time-varying state of polarization (SOP). This is supposed the optical field of extreme complexity in the time/frequency domain, and is expected to have unique applications in ultrafast plasmonics.
However, the requirement of creating two isolated pulse replicas in conventional ultrashort pulse measurement techniques, such as frequency-resolved optical gating (FROG), spectral phase interferometry for direct electric-field reconstruction (SPIDER), or tomographic ultrafast retrieval of transverse light E-fields (TURTLE) prevents them from being useful in OAW or V-OAW measurement. A limited number of measurement techniques are OAW or V-OAW compatible but subject to the requirements of a synchronized well-characterized optical reference, a synchronized radio-frequency (RF) reference, high-speed electronics, or large data redundancy and iterative algorithm. The usefulness of these methods could be compromised when the required optical or RF reference is unavailable, the system does not have interferometric stability, or the frequency comb spacing is larger than the attainable electronic bandwidth (e.g. 100 GHz).
In this dissertation, we proposed and experimentally demonstrated a couple of methods that can characterize as well as synthesize OAW or V-OAW without measurement ambiguity or requirements of interferometric stability, high-speed electronics, or iterative data inversion. The transform-limited pulse duration is 2.5 ps for the used comb source. They can be applied to attosecond extreme ultraviolet (EUV) pulse measurement and intensity repetition rate multiplication of a scalar or vectorial pulse train via temporal Talbot effect.

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