奈米尺度下的非線性頻率轉換至今仍然是個很大的挑戰，但其在許多領與諸如多功能光路、生物傳感、奈米光譜、奈米粒子操作及奈米醫學上都非常具有發展潛力。由於非線性光學對於電場強度的需求非常高，而局域性表面電漿此一現象由於能大幅地在局部提供極為強大的電場強度，因此非常適合用來產生非線性的訊號。而對於二次諧波產生來說，由於其產生機制的緣故，當我的使用的材料及結構為中心對稱時，即使能因局域性表面電漿產生極高的電場強度，其仍然無法產生二次諧波訊號。因此，若是想利用表面電漿共振產生二次諧波訊號的話，必須利用不對稱的材料或是利用不對稱的奈米結構。但事實上，還有另一種與局域表面電漿同屬表面電漿範疇的現象，也就是表面電漿子。在此研究的第一部分中，我們展示了一個以單晶金為材料且中心對稱的結構，雙線傳輸線，再利用表面電漿子做為光源以產生二次諧波訊號。並證明了即使在不打破對稱性的前提下，只要利用表面電漿子而非局域表面電漿，其仍然能夠產生二次諧波訊號
在第二部分的研究中，我們利用雙線傳輸線擁有兩種不同的傳遞模態的特性，並透過對稱模態及非對稱模態間的線性疊加，使表面電漿子訊號能集中往其中一條單線傳輸線傳遞，並透過將此種結構簡單地互相對接而製成一種電漿子光循環器。此種光循環器能夠藉由輸入不同的偏振態來改變其循環的方向。

Nonlinear optical frequency conversion in the nanoscale remains a challenge, but may pave the path towards the long envisaged multi-functional optical circuit, bio-sensing, nanospectroscopy, nanoparticle manipulation, and nanomedicine. Surface plasmon fields are highly spatially confined near the metal/dielectric interface and exhibit simultaneously giant field enhancement. These two attributes are invaluable for nonlinear optics with plasmons. However, second-harmonic generation (SHG) in bulk is forbidden in centro-symmetric materials such as typical noble metals. Past efforts concentrated on the broken symmetry at the surface in combination with an asymmetric shape of the particle.
We introduce a new way of breaking the symmetry by a propagating mode of a plasmonic waveguide, a two-wire transmission-line (TWTL). We demonstrate that an optical mode of correct symmetry is sufficient to allow SHG even in centro-symmetric structures made of centro-symmetric material. This is a new degree of freedom for on-chip nonlinear signal processing in nanophotonics.
A plasmonic circulator is also presented in this work. Due to TWTL have two different propagation mode. By simply superimposed the symmetric and anti-symmetric mode together, we can let SPP signal only focus on one side of the TWTL and cause SPP signal only propagation through one direction, and then make a circulator by this phenomenon. For this kind of circulator we can simply switch the direction by changing the polarization state of the input light source. We experimentally verified the functioning of the plasmonic circulator.

Acknowledgment I
摘要 III
Abstract IV
Table of Contents VI
Chapter 1 Introduction 1
1.1 Surface Plasmons 1
1.2 Static and Dynamic Plasmonic Field Control 2
1.3 Surface Plasmon Polaritons 3
1.3-1 Definition 3
1.3-2 SPP: Length Scales 4
1.3-3 SPP: Dispersion Relation 5
1.3.4 SPP: Wavelength 8
1.3.5 SPP: Polariton Propagation Length 8
1.3.6 SPP: Penetration Depth 9
Chapter 2 Plasmonic Two-Wire Transmission Line 10
2.1 Plasmonic Wave Guide 10
2.2 Two-Wire Transmission Line 10
2.3 Mode Profile of TWTL 11
2.4 Experimental Measurement 12
Chapter 3 Second Harmonic Generation in Two-Wire Transmission Line 15
3.1 Introduction 15
3.2 Theoretical Prediction 16
3.3 Numerical Simulation 18
3.4 Experimental Result 21
3.5 SH Anti-Symmetric Mode 22
3.6 Structure Design 27
3.6-1 Width of TWTL 27
3.6-2 Length of TWTL 30
3.6-3 Thickness of TWTL 33
Chapter 4 A Polarization-Actuated Plasmonic Circulator 35
4.1 Introduction 35
4.2 Working Principle 36
4.3 Structure Design and Experimental Measurement 39
4.3-1 Link Antenna 39
4.3-2 Dimer Antenna 46
4.3-3 Multi-Port Circulator 51
Chapter 5 Methods 53
5.1 Device Fabrication 53
5.2 Experimental Setup 53
5.3 Numerical Simulation 55
Chapter 6 Conclusions 56
References 59

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