宮本 克彦

Quantum state conversion from the higher-order polarization states of photons on a higher-order Poincaré sphere (HOPS) with spin angular momentum (SAM) and orbital angular momentum (OAM) to an electron system in a semiconductor host is an interesting topic for high-density quantum media conversion with high degrees of freedom (DoFs). In this paper, we present the spatial spin structure states of electrons on a higher-order Bloch sphere, corresponding to HOPS states, using the similarity between the electron states on the Bloch sphere and the polarization states on the Poincaré sphere. Furthermore, the coherent transfer of the spatial structure of photon polarization to the spin structure state of electrons was demonstrated for the first time in GaAs/AlGaAs quantum wells using a V-shaped three-level system. The results provide insights into the simultaneous coherent transfer of SAM and OAM from the extended states of photon-to-electron systems, leading to the realization of the quantum state transfer of the high-dimensional entangled states of photons to electron spins with different DoFs.

Skyrmions, topologically stable configurations of a three-component vector field with sophisticated textures, have been considered in many contexts, including atomic physics, Bose–Einstein condensates, liquid crystals, and magnetic materials. Although optical counterparts of skyrmions have extensively been studied theoretically and recently demonstrated in the laboratory experiments, their experimental mapping is challenging due to the fine, three-dimensional, and complicated structure of their polarization distributions. Here, we propose and demonstrate a straightforward mapping of the polarization textures of optical Néel-, Bloch-, and anti-skyrmions based on the radiation pressure and direct imprinting of the skyrmion textures on azopolymers. These results not only elucidate the exotic interaction that occurs between topologically protected quasiparticles of light and matter but also provide a simple approach for generation and characterization of optical skyrmions, based on a dual-path polarization shaping configuration with a single spatial light modulator, and their measurements based on the radiation pressure.

We demonstrate high-definition, direct-printing of micron-scale metallic dots, comprised of close-packed gold nanoparticles, by utilizing the optical vortex laser-induced forward transfer technique. We observe that the spin angular momentum of the optical vortex, associated with circular polarization, assists in the close-packing of the gold nanoparticles within the printed dots. The printed dots exhibit excellent electrical conductivity without any additional sintering processes. This technique of applying optical vortex laser-induced forward transfer to metallic dots is an innovative approach to metal printing, which does not require additional sintering. It also serves to highlight new insights into light–matter interactions.

Multicolor visible high-order Bessel (Bessel-vortex) beams which have a helical wavefront and a long confocal length have garnered significant interest for applications in materials processing and biomedical technologies. In this paper, we demonstrate the direct generation of multicolor (523, 605 and 637 nm) Bessel-vortex beams from a Pr³⁺-doped water-proof fluoro-aluminate glass (Pr³⁺: WPFG) fiber laser with an intracavity lens which induces chromatic and spherical aberration. The handedness of the generated Bessel-vortex beam is selectively controlled through lateral displacement of the intra-cavity lens.

We demonstrate the formation of surface relief structures in azo-polymers which exhibit multiple spiral arms, through irradiation of a rotating petal-like beam formed by the coherent superposition of Laguerre-Gaussian modes with opposite handedness. Intriguingly, the fabricated relief structures reflect full geometric parameters of the irradiated petal beam, such as handedness, topological charge, initial azimuthal phase and even ellipticity, corresponding to azimuthal and polar angles along equator and meridian planes of an orbital Poincaré sphere. The handedness, or direction of rotation, of the fabricated structures with multiple spiral arms could be controlled via the rotation and polarization directions of the irradiating laser field. This effect highlights an exotic coupling between the optical intensity gradient induced mass transport of the irradiated material and the spin angular momentum characteristics of the irradiating optical field. The azimuthal orientation of the surface relief structures could also be tuned by altering the initial relative phase between the coherently superposed Laguerre-Gaussian modes with opposite handedness, constituting the irradiating petal laser field. This work offers new insights into fundamental interactions which occur between light and matter, and we believe, will pave the way towards advanced technologies, such as ultrahigh density optical data storage.

We demonstrate a terahertz circular dichroism imaging to identify the structural chirality of twisted-layered moiré metasurfaces fabricated by nanoimprinting technology.

We report on the development of an ultrawideband and high-resolution THz spectroscopic system, which operates over a frequency range of 2–13.5 THz. This work goes beyond conventional THz spectroscopic measurements and demonstrates the capacity to differentiate D- and L-glucoses, which have the same molecular conformation and crystal structure. Furthermore, this system facilitates the structural identification of glucose microcrystals, which exists in α- and β-forms, revealing that L-glucose microcrystals are formed of a mixture of α- and β-D-glucose with approximately equal weight.

Abstract We generate a tunable (2.3–3 μm) optical vortex output with an order of 1 or 2 from a 1 μm optical-vortex-pumped singly resonant parametric oscillator based on a Mg doped periodically poled lithium niobate crystal. The orbital angular momentum (OAM) from the pump vortex beam was transferred to the mid-infrared idler output in this signal singly resonant high-Q cavity configuration. A maximum vortex output energy of 1.52 mJ was achieved within a wavelength tuning range of 2.27–2.96 µm. The signal beam with the Gaussian spatial profile was also generated within a 1.66–2 μm tuning range. The wide spectral bandwidth was experimentally measured near the wavelength degeneracy and explained by theoretically.

Abstract An optical vortex possesses a ring-shaped spatial profile and orbital angular momentum (OAM) owing to its helical wavefront. This form of structured light has garnered significant attention in recent years, and it has enabled new investigations in fundamental physics and applications. One such exciting application is laser-based material transfer for nano-/micro-fabrication. In this work, we demonstrate the application of a single-pulse optical vortex laser beam for direct printing of ring-shaped structures composed of hexagonal close-packed, mono-/multi-layered nanoparticles which exhibit ‘structural color’. We compare and contrast the interaction of the vortex beam with both dielectric and metallic nanoparticles and offer physical insight into how the OAM of vortex beams interacts with matter. The demonstrated technique holds promise for not only photonic-based nano-/micro-fabrication, but also as a means of sorting particles on the nanoscale, a technology which we term ‘optical vortex nanoparticle sorting’.

We demonstrate the direct printing of an ultrafine microdot formed of gold nanoparticles by employing optical vortex laser induced forward transfer. Spin and orbital angular momentum induces the close-packing and sintering of gold nanoparticles.

Laguerre-Gaussian (LG) modes [1] , [2] carry an annual spatial profile and a nonzero orbital angular momentum (OAM) owing to their on-axis phase singularity, and they offer us many applications, such as optical trapping and manipulation, laser nano/micro fabrication, super-resolution microscope, and optical communication.

Vector vortex beams, such as a radially or azimuthally polarized beam, have been widely investigated in many applications, including acceleration techniques [1] , high resolution microscopy [2] , materials processing [3] , [4] , and particle guiding or trapping [5]. The wavelength versatility of the vector vortex laser sources is strongly desired to explore these applications.

Azobenzene containing polymers (azopolymers) exhibit photo-induced mass transport via trans-cis/cis-trans photoisomerization cycles, thereby allowing the formation of reversible surface relief in an azo-polymer thin film [1]. Such photo-induced surface relief formation can be potentially applied to develop unique rewritable optical devices, such as rewritable optical circuits and rewritable optical data storages [2].

We present a simple single-pixel imaging system with a low mean squared error in the entire terahertz frequency region (3-13 THz) that employs a thin metallic ring with a series of directly perforated random masks and a subpixel mask digitization technique. This imaging system produces high pixel resolution reconstructed images, up to 1200 × 1200 pixels, and field of view of 1024 mm 2.

We demonstrate, for the first time, the fabrication of a monolayer photonic micro-ring formed of polydopamine coated monodisperse polystyrene particles by employing optical vortex induced forward mass transfer technique. Such interesting micro-ring formation will provide a new insight for interaction between the orbital angular momentum of light and matters.

We demonstrate, for the first time, the fabrication of a monolayer photonic micro-ring formed of polydopamine coated monodisperse polystyrene particles by employing optical vortex induced forward mass transfer technique. Such interesting micro-ring formation will provide a new insight for interaction between the orbital angular momentum of light and matters.

We propose continuously tunable terahertz-wave parametric source based on spectral drill cavity. When controlling of terahertz wave frequency by wavelength conversion using a nonlinear crystal, we have to control two laser beams. One is a frequency stabilized and intense pumping beam, and the other is a tunable seeding beam. We demonstrated an injection seeded optical parametric generator and amplifier as the pumping beam, a spectral drill cavity based ECDL as the seeding beam. Nonlinear wavelength conversion techniques are very promising for extending applied research into the terahertz region, and we expect that these will open up new research fields.

We discover that a flower-shaped surface relief on azo-polymer film is formed by irradiation of picosecond optical vortex pulses owing to nonlinear spatial modulation instability of optical vortex in azo-polymers.

We demonstrated single-longitudinal-mode, continuously tunable (1.54 - 1.60 μm) and pulsed ( 1 ns) parametric sources by injection-seeded PPLN-OPG / KTA-OPA as stabilized and tunable (controlled by 'spectral drill' cavity) beams for terahertz-wave different frequency / parametric generation.

We discover an entirely novel phenomenon, in which the optical vortex generates a spinning donor jet ('spin-jet') of an ultrahigh viscosity Au suspension. This phenomenon enables the super-resolution printing of Au particles.

We demonstrate the formation of chiral surface structure of azo-polymers via optical vortex induced two-photon-absorption (TPA). TPA-induced isomerization allows us to create the three-dimensional chiral structures with high longitudinal and transverse spatial resolution beyond the diffraction limit.

We demonstrate successfully the creation of a microscale lead halide perovskite crystal by employing optical vortex laser induced forward transfer (OV-LIFT) technology. The created microscale crystals exhibit efficient visible (cyan∼green∼red) fluorescence with a lifetime of ∼7 ns.

We report on the generation of a spinning twin-mode with two bright spots in a biomaterial, bacteriorhodopsin (bR), suspension pumped by an optical vortex. The spinning direction of the twin-mode is fully assigned by the handedness of the incident optical vortex. This phenomenon occurs owing to the spatial soliton effects in the bR suspension.

We demonstrate the formation of chiral surface relief of azo-polymers by irradiation of picosecond 1-μm optical vortex with a pulse width of 8ps via two-photon absorption. Optical vortex induced TPA enables us to create the chiral surface structures only within an extremely narrow defocusing tolerance with high three-dimensional (longitudinal and transverse) spatial resolution beyond the diffraction limit and without undesired outer rings of Airy pattern.

We report for the first time, to the best of our knowledge, a simple single pixel imaging (SPI) scheme with high singalto- noise ratio (SNR) in an entire THz frequency region (1 - 15 THz) by employing a thin metallic ring with a series of random masks directly perforated, that is a metallic randon ring'. This SPI scheme allows us to reconstruct highresolution images (320 x 320 pixels), and it offers potentially advanced THz imaging technologies, such as non-invasive assignment of biomaterials.