- Research
Optical nanoantennas couple with circularly polarized light to localize energy and chirality in subwavelength spaces.
Taguchi et al., Phys. Rev. Appl. (accepted).
Free-Form Nanophotonics: 3D Nanostructures and Near-Field Phenomena
As demonstrated in three-dimensional (3D) metamaterials, 3D nanophotonic structures have the potential to generate optical effects that cannot be realized in planar architectures. The design of such complex 3D nanophotonic structures can be facilitated by advanced machine-aided photonic design, such as topology optimization, enabling handling structures that are difficult to conceive through human intuition. This capability opens new possibilities for exploring intricate near-field phenomena, including chiral nanophotonics. We have developed a chiral nanogap antenna that selectively couples with circularly polarized light of a specific handedness. Detailed analysis of the associated near fields reveals the conversion of light’s spin angular momentum into optical chirality within nanoscale mode volumes. Our ultimate goal is to move beyond design, uncovering fundamental physics and engineering principles while establishing fabrication technologies to realize these structures for real-world applications.
DUV Light-Induced Deformation of Freestanding Thin Films
A giant deformation of a thin, freestanding sheet of ferroelectric BaTiO₃ was observed upon irradiation with solar-blind DUV light. The response time is 100,000 times faster than light actuators based on organic materials, such as those relying on photoisomerization. This discovery leads to new possibilities for the development of high-speed UV-light-driven actuators, enabling efficient conversion of light energy into mechanical motion while leveraging the superior chemical and mechanical stability of inorganic materials.
This work was conducted in collaboration with Dr. Tsukasa Katayama at the Research Institute for Electronic Science, Hokkaido University.
DUV light with a wavelength of 266 nm was intermittently irradiated onto a centimeter-scale single-crystal thin film of BaTiO₃.
Gong et al., ACS Appl. Mater. Interfaces 16, 54146 (2024).
Taguchi et al., J. Raman Spectrosc. 40, 1324 (2009); Taguchi et al. Appl. Phys. Lett. 101, 081110 (2012); Kawata, et al. Chem. Rev. 117, 4983 (2017); Taguchi et al., ACS Appl. Nano Mater. 3, 11434 (2020).
UV plasmonics & nanophotonics
Unlike gold and silver, which lose their metallic properties in the ultraviolet region, aluminum retains its metallic nature even in the deep ultraviolet (DUV) range. We discovered that aluminum nanoparticles and nanostructures can scatter and enhance DUV light. Building on this discovery, we are developing applications, including DUV near-field optical microscopy with aluminum probes, plasmon-enhanced UV photocatalysis, and nonlinear DUV light generation devices. Additionally, we are designing high-resolution objective lenses for ultraviolet applications, incorporating advanced reflection-type optics. Through collaborations with research groups and industry worldwide, we are developing practical optical imaging and 3D fabrication technologies, advancing the capabilities of DUV-based systems.
Nanomaterials & nano-imaging
At the nanoscale, materials exhibit optical, electrical, and quantum mechanical properties fundamentally different from their bulk counterparts. To address emerging challenges in materials science, we employ advanced techniques such as near-field spectroscopy and microscopy to visualize and analyze nanomaterials with nanoscale spatial resolution. Our goal is to develop cutting-edge imaging and analytical techniques, as well as instrumentation, to advance next-generation nano-optoelectronic and quantum devices. This field is particularly exciting, as traditional boundaries between photonics, electronics, chemistry, and mechanics dissolve, converging into a deeply interdisciplinary domain of nanoscience.
Taguchi et al., Nanoscale 7, 17424 (2015); Kawata, et al., Chem. Rev. 117, 4983 (2017); Deckert-Gaudig et al., Chem. Soc. Rev. 46, 4077 (2017); Saitoh, et al., APL Photon. 4, 021301 (2019).