臺灣博碩士論文加值系統

介於遠紅外光與微波之間的電磁波，其頻率範圍在0.1~30 terahertz (or THz, 1THz=1012Hz) 的波段，稱之為兆赫波(THz wave)。在傳統的電磁學研究中，對於這個波段的電磁波並沒有多所著墨，於是在電磁波頻譜的研究中便留下了一個兆赫波波段的斷層，而這樣的現象也被稱之為所謂電磁波頻譜中的“兆赫波鴻溝(terahertz gap)”。
在本論文中，我們建立一套兆赫波的產生與檢測系統，分別利用光電導模式(Photoconduction)及電光取樣(Electro-Optical Sampling)的方法，來產生與偵測兆赫波，並利用此系統研究以不同的InP表面-本徵-N+ (SIN+) 微結構之樣品做為輻射器(emitter)所產生之兆赫波訊號。藉由光調制光譜學(PR)量測半導體輻射器的內建電場，驗證了位於半導體中不同層的電場，會產生不同的兆赫波訊號，並探討各種不同結構的輻射器所輻射的兆赫波其強度與輻射器結構、內建電場的關係。此外，我們也建立一套自相干儀(autocorrelator)系統，對兆赫波實驗系統中鈦-藍寶石(Ti:Sapphire)脈衝雷射的脈衝寬度隨時做監控。

Terahertz (THz) radiation (THz waves), electromagnetic radiation in a frequency interval from 0.1 to 30 THz, is the next frontier in imaging science and technology. THz waves, or T-rays, occupy a large portion of the electromagnetic spectrum between the infrared and microwave bands. However, compared to relatively well-developed medical imaging at microwaves and optical frequencies, basic research, new initiatives and advanced technological developments in the THz band are very limited.
In this thesis, we present the details of our work which has successfully set up a system to generate and detect the terahertz waves. Photoconductive technique is used for radiation generation while electro-optical sampling is employed in the radiation detection. Electro-optical crystal ZnTe is used as the radiation sensor while GaAs wafer and various semiconductor surface intrinsic-N+ (SIN+) microstructures are used as the radiation emitters. The dependences of the intensities and frequency ranges of the THz waves, radiated from InP SIN+ structures, on the built-in electric field, top layer thickness of the structures and pumping power density are investigated.
Ti: Sapphire pulse laser with 80 femtosecond (fs) pulse width is used to pump and probe the THz radiation. Since the radiation power and spectrum are also strong related to the pulse width (80 femtosecond), an autocorrelator is also set up to monitor the pulse width of the laser pulse width.

第一章 緒論 .............................................1
第二章 兆赫輻射波產生與偵測系統..........................6
第2-1節 兆赫波輻射與偵測系統之實驗裝置..............6
第2-2節 輻射機制與原理.............................12
2-2-1 光電導效應.............................12
2-2-2 非線性效應─ 光整流(optical rectification)、
合頻(sum of frequency)、
差頻(difference of frequency)效應............15
第2-3節 自由空間電光取樣偵測方法...................18
第2-4節 結論.......................................23
第三章 利用半導體材料InP產生兆赫波之研究...............24
第3-1節 樣品結構...................................24
第3-2節 光調製光譜學之量測.........................27
第3-3節 InP產生之兆赫波訊號........................31
3-3-1 不同的激發光強度........................31
3-3-2 不同的頂層厚度..........................35
3-3-3 不同的基板摻雜..........................38
第3-4節 結論.......................................45
第四章 自相干儀系統.....................................47
第4-1節 實驗裝置...................................47
第4-2節 脈衝半高寬(FWHM)計算......................50
第4-3節 GVD(group velocity dispersion)
補償效應的計算.............................54
第五章 總結.............................................56
參考文獻.................................................58

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