근접장 광학 현미경 탐침을 이용한 빛의 전기장 성분의 3차원 매핑

학위논문(박사)--서울대학교 대학원 :자연과학대학 물리·천문학부,2015. 2. 김대식.In this thesis, I measured the direction of local electric field vectors in three-dimensional space with 100 nm resolution. A radial polarized light is generated by using a radial polarization converter and is focused by an objective lens. Gold nanoparticle functionalized probes are used as the local probes which scatter the focused field into the far-field region. The optical scattering properties of the gold nanoparticle functionalized probes are characterized by determining the polarizability tensors of them. I used rotational analyzer ellipsometry and Stokes parameters to reconstruct the local polarization states of the focused radial polarized light. Two distinct methods give consistent results with each other. I performed near-field measurements of transmission through nanometer-sized gaps at near infrared frequencies with varying the gap size from 1 nm to 10 nm. Field enhancement factors of the nanogaps were quantified by measuring transmission of the nanogaps using NSOM. The near-field measurements produce consistent result to the far-field measurement on quantifying the field enhancement factors of the nanogaps. In spite of the consistency, the near-field measurements have advantages of low background and accessibility to a single nanostructure. I demonstrated the mapping of optical magnetic field of the focused radial polarized light. Subwavelength apertures on metal films and on the apex of tapered fiber probes used as the local probes of the optical magnetic field. By scanning the apertures at the focal plane, I measured the optical magnetic field distribution of the focused radial polarized light. I compared the scattered signal from the apex of the conical probe and the collected signal through the aperture on the apex of the probe. From the measurements, I conclude that subwavelength apertures on the apex of the conical probe are sensitive to the horizontal components of the optical magnetic field. I fabricated near-field scanning optical microscopy (NSOM) probes with different geometrical factors which determine the selective sensitivity to the electric field and the magnetic field of light. The physical parameter dominating the preferential sensitivity is found to be the width of the metal rim surrounding aperture. I quantified the coupling ratio of the NSOM probes to the optical electric and magnetic field by measuring the scattering polarization of the probes. Using the characterized NSOM probes, I measured electromagnetic field distribution of vertical standing wave formed upon reflection at oblique incidence on a metal film. The vertical profiles of the collection signal from two different kinds of probes, the electric probes and the magnetic probes, appear to be out-of-phase.Table of Contents Chapter 1 Introduction ............................................................. 1 Chapter 2 Fabrication of near-field probes ................................................................... 7 2.1 Fabrication of gold nanoparticle functionalized probes ................................................................... 7 2.2 Fabrication of metal-coated apertured probes ................................................................. 10 Chapter 3 Experimental Setups ................................................................. 13 3.1 Near-field Scanning Optical Microscopy .......................................................... 13 3.1.1 Feed-back and Scanning system ................................................................ 13 3.1.2 Optical detection system ................................................................ 15 3.2 Three-dimensional optical vector field mapping setup ................................................................... 19 3.2.1 Optical illumination and Scanning system ................................................................ 19 3.2.2 Optical detection system ................................................................ 22 Chapter 4 Theoretical descriptions ......................................................... 25 4.1 Dipole radiation .............................................................. 25 4.2 Field distribution of radially polarized light .................................................................... 29 4.3 Field distribution at the nanogap ............................................................. 33 Chapter 5 Three dimensional optical vector field mapping ............................................................. 51 5.1 Analysis of local polarization state ................................................................... 51 5.2 Tip characterization.................................................... 57 5.3 Three-dimensional vector field mapping of focused radially polarized light .................................................................... 59 Chapter 6 Quantification of field enhancement factor of nanometer-sized gaps ................................................................... 65 6.1 Fabrication of nanogap samples .............................................................. 65 6.2 Far-field transmission measurements...................................................... 69 6.3 Near-field transmission measurements ..................................................... 73 Conclusion .......................................................... 81 Appendices .......................................................... 83 Chapter A.1 Optical magnetic field mapping of radial polarized light ..................................................................... 83 A.1.1 Bethe-Bouwkamp aperture on a metal film ...................................................................... 83 A.1.2 Bethe-Bouwkamp aperture on the apex of the conical probe ................................................................... 89 Chapter A.2 Selective detection of transverse component of electric and magnetic field of light ..................................................................... 97 A.2.1 Discrimination of Electric Probe and Magnetic Probe ................................................................... 97 A.2.2 Quantitative Estimation of Electric and Magnetic Field Coupling Coefficients ...........................................................101 A.2.3 Origin of Selective Electric and Magnetic Field Sensitivity of NSOM Probes ..................................................................105 A.2.4 Mapping Hertzs standing wave at optical frequency .............................................................109 References .......................................................... 113 요약 (국문초록) ...................................................................... 119 List of publications ................................................ 120 Conferences ........................................................ 122Docto