arXiv subjects

Katsuhiko Miyamoto

Publications and source records attributed to Katsuhiko Miyamoto.

6 recordsLinked to original sources

arXiv2023

Higher-order Bloch spheres: A generalized representation of electron spin states with azimuthal phase factor

Using the similarity between spin states on the Bloch sphere (BS) and polarization states on the Poincare sphere (PS), we construct higher-order spin states on the higher-order BS corresponding to higher-order polarization states of photons on the higher-order PS. We investigate the time evolution of higher-order spin states in a magnetic field and establish an extended form of the conventional Larmor precession. The results provide insights on coherent transfer from extended photons to extended spin qubit systems with spin and orbital angular momenta and the operation of extended spin qubits.

quant-ph↗

arXiv2020

Broadband high-resolution terahertz single-pixel imaging

We report 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 x 1200 pixels, and imaging area of 32 mm x 32 mm. It can be extended to develop advanced imaging systems in the near-ultraviolet to terahertz region.

physics.optics↗

arXiv2020

Investigation of laser-induced-metal phase of $\mathrm{MoTe}_{2}$ and its contact property via scanning gate microscopy

Although semiconductor to metal phase transformation of MoTe$_{2}$ by high-density laser irradiation of more than 0.3 MW/cm$^{2}$ has been reported, we reveal that the laser-induced-metal (LIM) phase is not the 1T' structure derived by a polymorphic-structural phase transition but consists instead of semi-metallic Te induced by photo-thermal decomposition of MoTe$_{2}$. The technique is used to fabricate a field effect transistor with a Pd/2H-MoTe$_{2}$/LIM structure having an asymmetric metallic contact, and its contact properties are studied via scanning gate microscopy. We confirm that a Schottky barrier (a diffusion potential) is always formed at the Pd/2H-MoTe$_{2}$ boundary and obstacles a carrier transport while an Ohmic contact is realized at the 2H-MoTe$_{2}$/LIM phase junction for both n- and p-type carriers.

cond-mat.mtrl-sci↗

arXiv2019

Generation of high-quality terahertz OAM mode based on soft-aperture difference frequency generation

We demonstrate the generation of high-quality tunable terahertz (THz) vortices in an eigenmode by employing soft-aperture difference frequency generation of a vortex output and a Gaussian mode. The generated THz vortex output exhibits a high-quality orbital angular momentum (OAM) mode with a topological charge of $\ell_{THz}=\pm1$ in a frequency range of 2-6 THz. The maximum average power of the THz vortex output obtained was ~3.3 $μ$W at 4 THz.

physics.optics↗

arXiv2019

Generation of coupled orbital angular momentum modes from an optical vortex parametric laser source

We report on the generation of flower (wheel) modes, which manifest coupled orbital angular momentum (OAM) modes, from a vortex pumped optical parametric oscillator simply by employing a pump source with a short temporal coherence time. This vortex oscillator was also developed to generate a further higher-order vortex signal output with $l_s=2-4$ by replacement of the pump source with a longer coherence time. The signal and idler outputs were tuned within wavelength ranges of 745-955 nm and 1200-1855 nm, respectively. The maximum signal output energy of 1.2 mJ was measured with an optical efficiency of 15.6%.

physics.optics↗

arXiv2019

Optical vortex-induced forward mass transfer: Manifestation of helical trajectory of optical vortex

The orbital angular momentum of an optical vortex field is found to twist high viscosity donor material to form a micron-scale 'spin jet'. This unique phenomenon manifests the helical trajectory of the optical vortex. Going beyond both the conventional ink jet and laser induced forward mass transfer (LIFT) patterning technologies, it also offers the formation and ejection of a micron-scale 'spin jet' of the donor material even with an ultrahigh viscosity of 4 Pas. This optical vortex laser induced forward mass transfer (OV-LIFT) patterning technique will enable the development of next generation printed photonic/electric/spintronic circuits formed of ultrahigh viscosity donor dots containing functional nanoparticles, such as quantum dots, metallic particles and magnetic ferrite particles, with ultrahigh spatial resolution. It can also potentially explore a completely new needleless drug injection.

physics.optics↗