Near-Field Imaging of Magnetic Domains
Gereon Meyer, Andreas Bauer, Giinter Kaindl ................... 1
1. Introduction .................................................. 1
2. Magneto-Optical SNOM .......................................... 2
2.1. Faraday Effect and Kerr Effect ........................... 2
2.2. Sagnac Interferometer .................................... 4
2.3. Kerr Microscopy .......................................... 7
2.4. Domain Contrast in SNOM .................................. 8
3. Experimental Details ......................................... 11
3.1. UHV System .............................................. 11
3.2. UHV-SNOM Setup .......................................... 14
3.3. Sagnac-SNOM Setup ....................................... 16
3.4. Performance Tests ....................................... 18
4. Magnetic Domains in Ultrathin Films .......................... 23
4.1. Spin-Reorientation Transition ........................... 24
4.2. Stripe-Domain Patterns .................................. 25
4.3. Domain Contrast ......................................... 27
4.4. Study of Magnetization Reversal ......................... 30
4.5. Transformation of Stripe Domains ........................ 33
5. Summary and Future Prospects ................................. 36
References ...................................................... 38
Improvement of Interface Quality in Cleaved-Edge-Overgrowth
GaAs Quantum Wires Based on Micro-optical Characterization
Masahiro Yoshita, Hidefumi Akiyama ........................... 43
1. Introduction ................................................. 43
2. T-Shaped Quantum Wires Grown by Cleaved-Edge Overgrowth
Metliod ...................................................... 44
2.1. Cleaved-Edge Overgrowth Method with MBE ................. 44
2.2. Micro-PL Imaging and Spectroscopy Setup
to Characterize T Wires ................................. 46
2.3. PL of T Wires Grown by the Original CEO Method .......... 47
3. Interface Roughness and Modulated Electronic States
in (110) GaAs QWs ............................................ 48
3.1. Preparation of (110) GaAs QWs ........................... 48
3.2. Macro-PL of the (110) GaAs QWs .......................... 49
3.3. Micro-PL Spectroscopy of the (110) GaAs QWs ............. 50
3.4. Interface Roughness in the (110) GaAs QWs
and T Wires Grown by the CEO Method ..................... 54
4. Formation of an Atomically Flat Surface on the (110)
GaAs Grown by the CEO Method ................................. 54
4.1. Atomic Arrangements of the (001)
and (110) GaAs Surfaces ................................. 55
4.2. Growth-Interrupt in situ Annealing Technique ............ 56
4.3. Formation of Atomically Flat CEO Surfaces
by Growth-Interrupt Annealing ........................... 56
4.4. Surface Morphology of the Annealed Surface
with Fractional Monolayer Coverage ...................... 59
4.5. Step-Edge Kinetics on the (110) GaAs Surface
during Annealing ........................................ 61
4.6. First-Principles Calculations of Adatom Migration
Barrier Energies on (110) GaAs .......................... 64
4.7. Toward Formation of a Wider Atomically Flat (110)
GaAs Surface ............................................ 67
5. Fabrication of a High-Quality (110) GaAs QW with
Atomically Smooth Interfaces ................................. 67
5.1. Preparation of a (110) GaAs QW with Atomically
Smooth Interfaces ....................................... 69
5.2. Micro-PL of the (110) GaAs QW ........................... 69
6. Fabrication of a High-Quality Single-Quantum-Wire
Laser Structure and its Lasing Properties .................... 73
6.1. Preparation of a Single-T-Wire Laser Structure .......... 73
6.2. Spatial Uniformity of the Electronic States in the
T Wire ................................................. 75
6.3. Lasing from a Single-Quantum-Wire Laser ................. 76
7. Concluding Remarks and Future Perspective .................... 77
References ...................................................... 79
Recombination Dynamics in InxGa1-xN-Based Nanostructures
Yoichi Kawakami, Akio Karieta, Kunimichi Omae,
Yukio Narukawa, Takashi Mukai ................................ 83
1. Introduction ................................................. 83
2. Material Parameters of InxGa1-xN .............................. 85
2.1. Bandgap Energies in InxGa1-xN Alloys ................... 85
2.2. Alloy Broadening Factor in InxGa1-xN Alloys .............. 86
2.3. Piezoelectric Fields in Strained InxGa1-xN Layers ........ 87
3. General Transition Models .................................... 89
3.1. Localization versus Screening of Piezoelectric Field .... 89
3.2. Photoinduced Change of Optical Density Induced
by Two Major Effects .................................... 92
4. Pump and Probe Spectroscopy on InxGa1-xN Thin Layers
and Quantum Wells ............................................ 95
5. SNOM-Luminescence Mapping Results ........................... 100
5.1. Instrumentation ........................................ 100
5.2. SNOM-PL Mapping at Low Temperature under
Illumination-Collection Mode ........................... 104
5.3. Multimode SNOM at RT ................................... 113
6. Conclusion .................................................. 121
References ..................................................... 122
Quantum Theory of Radiation in Optical Near Field
Based on Quantization of Evanescent Electromagnetic Waves
Using Detector Mode
Tetsuya Inoue, Hirokazu Hori ................................ 127
1. Introduction ................................................ 127
1.1. Half-Space Problems and Angular-Spectrum
Representation ......................................... 128
1.2. Quantization of Evanescent Electromagnetic Fields
and Radiative Decay in Optical Near Field .............. 130
1.3. Detector-Mode Description for Radiation Problem ........ 131
1.4. Outline ................................................ 132
2. Classical Theory of Radiation from an Oscillating
Electric Dipole in Free Space ............................... 133
2.1. Dipole Radiation in Free Space ......................... 133
2.2. Total Radiation Intensity in Free Space ................ 137
3. Classical Theory of Radiation Based on Angular-Spectrum
Representation .............................................. 139
3.1. Angular-Spectrum Representation ........................ 140
3.2. Angular-Spectrum Representation of Scattered
Electromagnetic Fields ................................. 142
3.3. Angular Spectrum of Dipole Radiation Fields
in Optical Near-Field Regime ........................... 146
3.4. Evaluation of Radiation Based on Angular-Spectrum
Representation ......................................... 148
4. Radiative Decay of Oscillating Electric Dipole in
Half-Space Based on Angular-Spectrum Representation ......... 150
4.1. Half-Space Problems .................................... 150
4.2. Angular-Spectrum Representation of Radiation Fields
in Half-Space .......................................... 154
4.3. Electric Dipole Radiation into Medium .................. 156
4.4. Electric Dipole Radiation into the Vacuum-Side
Half-Space ............................................. 157
4.5. Interaction between Electric Dipole and Dielectric
Surface ................................................ 158
5. Quantum Theory of Dipole Radiation Near a Dielectric
Surface Based on Detector Modes ............................. 161
5.1. Normal Modes as the Basis of Field Quantization
in Half-Space Problems; Triplet and Detector Modes ..... 162
5.2. Detector-Mode Functions ................................ 165
5.3. Electric Field Operator in Half-Space Problems ......... 168
5.4. Spontaneous Emission into Right Half-Space ............. 170
5.5. Spontaneous Emission into Left Half-Space .............. 172
5.6. Radiative Decay Rate and Lifetime of Electric
Dipole in Half-Space ................................... 173
5.7. Dependence of Radiative Lifetime on Magnetic
Quantum Number of Atom in Half-Space Problems ............... 176
6. Quantum Theory of Multipole Radiation in Optical
Near-Field Regime ........................................... 181
6.1. Multipole Transition Matrix Elements ................... 182
6.2. Spontaneous Decay Rate of Multipoles in Half-Space ..... 184
7. Tunneling Picture of Optical Near-Field Interactions ........ 188
7.1. Energy Transport via Tunneling in Optical
Near-Field Interactions ................................ 189
7.2. Fundamental Process in Nano-Optics Device .............. 192
Appendices .................................................. 193
A. Vector Spherical Wave ....................................... 193
В. Expansion of the Vector Plane Wave in Terms
of the Vector Spherical Waves ............................... 195
С. Multipole Expansion of Transition Current ................... 196
References ..................................................... 198
Index .......................................................... 201
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