光第二高調波発生と光和周波発生による凝集体の空間反転対称性の破れの観察

抄録

  Optical second harmonic generation (SHG) and sum frequency generation (SFG) are second-order nonlinear optical responses of matter. When two intense light pulses with photon energies ℏω₁ and ℏω₂ enter a solid, a new light pulses with photon energy ℏω₁+ℏω₂ can be generated. This phenomenon is called SHG when ω₁=ω₂, and SFG when ω₁≠ω₂. Within the electric dipole approximation, SHG and SFG have a unique property of being allowed for media without spatial inversion symmetry. In this paper, I describe examples of analyses of a photocatalyst material titanium dioxide (TiO₂), metal nanowire arrays, hydrogen-terminated Si(111) surfaces, and chiral biomaterials, by SHG/SFG spectroscopic or microscopic observation. I will pay special attention to a viewpoint of inversion symmetry breaking causing SHG or SFG in each material.