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

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44 9 0 8 5 8 0 7 5 7 0 6 5 6 0 Chapter 3 Excitation of surface plasmon polaritons 0 2 0 0 4 0 0 6 0 0 8 0 0 1 0 0 0 tim e [s ] Figure 3.8: Dark signal of the photo-detector over time. an applied voltage of 10 V, and R2 = 10 MΩ this will yield ≈ 0.4 µV/ √ Hz. Laser stability Having established the noise floor of the photo-detector it is now possible to test the stability of the laser diode. For this purpose the laser diode is focused on the reference photo-detector (detector 1 in Fig. 3.1). The detected Uout as a function of time for the illuminated and the dark photo-detector is shown in Fig. 3.9. The figure shows for the illuminated photo-detector a photovoltage of about 1.6 mV with a standard deviation of ±2.9 µV. This is about the same noise floor as for the dark detector, hence the laser diode does hardly contribute to the noise floor. The noise of about ±2.9 µV corresponds to ≈ ±0.2% of the background signal of about 1.6 mV. As mentioned before, Uout scales linearly with the laser intensity. Thus, a ±0.2% change in Uout is acceptable, compared to the change in reflectivity of the simulated curves in Sect. 2.4 which is at least 1%.
Section 3.2 Calibration 45 U o u t [m V ] 1 .6 2 1 .6 1 1 .6 0 1 .5 9 la s e r d a rk 2 0 0 4 0 0 6 0 0 8 0 0 1 0 0 0 tim e [s ] Figure 3.9: The black curve shows Uout as a function of time, when the laser diode illuminates the reference photodiode. The red curve shows the dark signal of the photo-detector. Resolution limit of the voltmeter So far, measurements are discussed for which the output voltage of the photo-detector was recorded directly by a 195A voltmeter from Keithley. However, the surface plasmons experiments typically require the measurement of small intensity changes on a large constant background intensity. To circumvent limitations due to the finite digitalisation depth a differential (A-B) technique is used. To this end, a potentiometer is connected in parallel to the power supply of the laser diode. This allows to source a constant voltage of 0 ≤ UB ≤ 5 V to the input B of a JFET preamplifier (SIM 910) from Stanford Research Systems. The output of the photo-detector is connected to input A, and the output of the preamplifier is connected to a SIM 970 voltmeter from Stanford Research Systems, as shown in Fig. 3.10. This technique allows to subtract a constant level from the detected signal, so that only the smaller difference Uout − Uref is measured. Because this difference is much smaller than the signal itself it is possible to increase the signal resolution and circumvent digitalisation issues. 0 .0 9 0 .0 8 0 .0 7 0 .0 6 U o u t [m V ]
Page 1: TECHNISCHE UNIVERSITÄT MÜNCHEN WA
Page 4 and 5: II Contents 4.2 Reflectivity of mul
Page 6 and 7: 2 Chapter 1 Introduction via a grat
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 50 and 51: 46 5 V 0 V U out Chapter 3 Excitati
Page 54 and 55: 50 U A-B (θ) [V] 0.00 -0.05 -0.10
Page 56 and 57: 52 U A -B (θ) [V ] U A (θ) [V ] U
Page 58 and 59: 54 will be discussed. 4.1.1.2 Deter
Page 60 and 61: 56 p R 1 .0 0 .8 0 .6 0 .4 0 .2 0 .
Page 62 and 63: 58 p R 0 .8 0 .4 0 .0 0 .8 0 .4
Page 64 and 65: 60 Chapter 4 Experimental study of
Page 70 and 71: 66 4.4 Summary Chapter 4 Experiment
Page 74 and 75: 70 Chapter 5 Surface plasmons in ma
Page 76 and 77: 72 U A -B , -1 5 m T (θ) [V ] 0 .0
Page 80 and 81: 76 Δ θ 0 2 0 1 5 1 0 5 0
Page 84 and 85: 80 ΔU θ = c o n s t (θ) [m V ]
Page 88 and 89: 84 p x 1 0 -4 p /δθ 1 /R δR 0 .5
Page 90 and 91: 86 δU /U (H ) x 1 0 -3 2 .5 2 .0 1
Page 94 and 95: 90 s M /M 1 .5 1 .0 0 .5 0 .0 -0 .5
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94 Chapter 6 Conclusions and Outloo
Page 100 and 101:
Page 102 and 103:
Page 104 and 105:
100 Chapter 6 Conclusions and Outlo
Page 106 and 107:
102 (*Thickness of the layers in An
Page 108 and 109:
104 /Extract[Ms[lambda, theta], {1,
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106 40 mm 10 mm 130 mm Figure B.2:
Page 112 and 113:
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
Page 120 and 121:
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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