Surface magneto-plasmons in magnetic multilayers - Walther ...

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2 Chapter 1 Introduction via a grating into waveguides, metallic slabs embedded in a dielectric, what allows for subwavelength optics [13]. Moreover, in recent years the interaction of an external applied magnetic field with surface plasmons in multilayers, especially in Au/Co/Au multilayers, became another focus of attention [14, 15, 16]. The corresponding experiments are based on theoretical work by Chiu and Quinn [17] presented in 1972, where they theoretically described the influence of a magnetic field on the dispersion relation of surface magneto-plasmon waves in a metal. The influence of the magnetic field strongly depends on the orien- tation of the field vector with respect to the incident plane of light and to the sample surface. In this thesis, the transversal geometry is regarded, meaning that the magnetic field vector is parallel to the sample surface but perpendicular to the plane of incidence of light, and hence the magnetic field vector is also perpendicular to the propagation of the surface plasmon. In the presence of a magnetic field off-diagonal components appear in the dielectric tensor, which depend on the so-called Voigt con- stant [18]. Furthermore, this causes the surface plasmon dispersion relation to be dependent on the propagation direction of the surface plasmon, what in turn affects the surface plasmon resonance angle θSPP. This magnetic field dependence of the surface plasmon resonance opens the way for future applications such as magneto-plasmonic modulators [19], magneto-plasmonic sensors [20], or optical isolators [21]. Due to this recent interest it is the aim of this thesis to study angle resolved surface plasmon resonances in the Kretschmann-Raether configuration in the presence of an external magnetic field. To this end, we assembled a setup, to detect angle resolved surface plasmon resonances of single and multilayer films. Using this setup we investigated the behaviour of surface plasmons in presence of an external magnetic field. The thesis is organised as follow: In Chapter 2 the theoretical considerations of surface plasmons are briefly reviewed. These considerations start with the Maxwell equations and yield the dispersion relation of surface plasmons. By comparing the dispersion relation of surface plasmons with the dispersion relation of light, the condition for surface plasmon resonance as function of light incident angle is obtained. With the then introduced concept of the reflection of a multilayer structure, the surface plasmon resonance is simulated. Simulations for different multilayers are shown and compared.
The setup to detect these angle dependent surface plasmon resonances and its components are described in Chapter 3. Furthermore, in this chapter, calibrations of the used detector and the alignment procedure are discussed. Next, in Chapter 4 the experimental study of surface plasmon resonances in single- and multilayer films is presented. The measured resonances are compared to the simulations from Chapter 2 and the differences between measurements and simulations are critically discussed. Then, the influence of a magnetic field on the surface plasmon resonance curves is investigated for different samples in Chapter 5. The results obtained in this thesis are compared with measurements from the literature. In Chapter 6 a conclusion of the results is given and from this further experiments are proposed. 3
Page 1: TECHNISCHE UNIVERSITÄT MÜNCHEN WA
Page 4 and 5: II Contents 4.2 Reflectivity of mul
Page 8 and 9: 4 Chapter 1 Introduction
Page 10 and 11: 6 angular frequency, t the time, an
Page 12 and 13: 8 Chapter 2 Theory Here, µ (1) =
Page 14 and 15: 10 electron density. Chapter 2 Theo
Page 16 and 17: 12 Chapter 2 Theory [8]. In this co
Page 18 and 19: 14 2.3.1 Reflectivity of a single l
Page 20 and 21: 16 Chapter 2 Theory curve shown in
Page 22 and 23: 18 t 10 t 10 t 10 r 01 E 0 r 10 e i
Page 24 and 25: 20 Chapter 2 Theory Hereby, i = 1,
Page 26 and 27: 22 2.4 Simulation of the reflectivi
Page 28 and 29: 24 dopt = |ε ′(1) | − 1 4π |
Page 30 and 31: 26 p R 1 .0 0 .8 0 .6 0 .4 0 .2 0 .
Page 32 and 33: 28 2.5.1 Interaction of an external
Page 34 and 35: 30 ω |k x | Chapter 2 Theory Figur
Page 36 and 37: 32 Chapter 2 Theory enhancement wil
Page 38 and 39: 34 LASER lter beam splitter polaris
Page 40 and 41: 36 (a) εsubstrate εCo ε prism ε
Page 42 and 43: 38 Chapter 3 Excitation of surface
Page 46 and 47: 42 p h o to -d e te c to r s ig n a
Page 48 and 49: 44 9 0 8 5 8 0 7 5 7 0 6 5 6
Page 50 and 51: 46 5 V 0 V U out Chapter 3 Excitati
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52 U A -B (θ) [V ] U A (θ) [V ] U
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54 will be discussed. 4.1.1.2 Deter
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56 p R 1 .0 0 .8 0 .6 0 .4 0 .2 0 .
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58 p R 0 .8 0 .4 0 .0 0 .8 0 .4
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60 Chapter 4 Experimental study of
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66 4.4 Summary Chapter 4 Experiment
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70 Chapter 5 Surface plasmons in ma
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72 U A -B , -1 5 m T (θ) [V ] 0 .0
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76 Δ θ 0 2 0 1 5 1 0 5 0
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80 ΔU θ = c o n s t (θ) [m V ]
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84 p x 1 0 -4 p /δθ 1 /R δR 0 .5
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86 δU /U (H ) x 1 0 -3 2 .5 2 .0 1
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90 s M /M 1 .5 1 .0 0 .5 0 .0 -0 .5
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94 Chapter 6 Conclusions and Outloo
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100 Chapter 6 Conclusions and Outlo
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102 (*Thickness of the layers in An
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104 /Extract[Ms[lambda, theta], {1,
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106 40 mm 10 mm 130 mm Figure B.2:
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108 and d sin 45 = h/2 sin(90 + θ)
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110 Appendix C Prism correction
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112 Appendix D Code for SPP simulat
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114 (*MO Reflectivity*) Appendix D
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116 Bibliography [12] J. Weeber, E.
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118 Bibliography [40] A. A. Maradud
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120 Bibliography [67] F. E. Luborsk
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122 Bibliography [93] T. Sidiropoul
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Robert Müller, Helmut Thies and hi
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