Kuniaki Konishi

We demonstrate circularly polarized light emission from InAs quantum dots embedded in the waveguide region of a GaAs-based chiral nanostructure. The observed phenomenon originates due to a strong imbalance between left- and right-circularly polarized components of the vacuum field and results in a degree of polarization as high as 26% at room temperature. A strong circular anisotropy of the vacuum field modes inside the chiral nanostructure is visualized using numerical simulation. The results o

The discrete rotational symmetry of nanostructures provides a powerful and simple guiding principle for designing the second-harmonic generation process in nonlinear metamaterials. We demonstrate that, in achiral nanostructures with threefold rotational symmetries, a circularly polarized fundamental beam produces a countercircularly polarized second-harmonic beam. In this case, the polarization state of the second harmonic is determined in a very simple manner. We also demonstrate how rotational

We examine the mechanism responsible for the optical activity of a two-dimensional array of gold nanostructures with no mirror symmetry on a dielectric substrate. Measurements with different incident angles, polarizations and sample orientations allow us to reveal that observed polarization effect is enhanced by surface plasmon resonance. By performing numerical simulation with rigorous diffraction theory we also show that the grating chirality can be described in terms of the non-coplanarity of

Control of light polarization is a key technology in modern photonics including application to optical manipulation of quantum information. The requisite is to obtain large rotation in isotropic media with small loss. We report on extraordinary optical activity in a planar dielectric on-waveguide photonic crystal structure, which has no in-plane birefringence and shows polarization rotation of more than 25 degrees for transmitted light. We demonstrate that in the planar chiral photonic crystal,

Circularly polarized light in the vacuum ultraviolet (VUV) region is important for probing the structural and electronic properties of matter. Moreover, a circularly polarized VUV coherent light enables one to observe the dynamics of biomolecules and electron spins in solids. The development of a table-top technology to directly generate circularly polarized VUV coherent light is of great value, owing to the limitation of polarization control elements for the VUV region. However, solid-state non

Controlling polarization using metamaterials has been one of the research areas that attract immense attention. In particular, the symmetry of the structure plays an important role in controlling polarization-sensitive optical phenomena. Circular polarization control, which is used for important applications such as circular dichroism spectroscopy, requires designing the symmetry of a metamaterial with circular polarization eigenstates. In the linear response, a giant optical activity was observ

Deep-ultraviolet (DUV) light is essential for applications including fabrication, molecular research, and biomedical imaging. Compact metalenses have the potential to drive further innovation in these fields, provided they utilize a material platform that is cost-effective, durable, and scalable. In this work, we present aluminum nitride (AlN) metalenses as an efficient solution for DUV applications. These metalenses, with a thickness of only 380 nm, deliver DUV focusing and imaging capabilities

Tunable coherent light sources operating in the vacuum ultraviolet (VUV) region in the 100–200-nm (6–12 eV) wavelength range have important spectroscopic applications in many research fields, including time-resolved angle-resolved photoemission spectroscopy. Recent advances in laser technology have enabled the upconversion of visible femtosecond lasers to the vacuum and extreme ultraviolet regions. However, the complexity of their experimental setups and the scarcity of bulk nonlinear crystals f