Ryoichi Sakata

Mechanical-free, high-power, high-beam-quality two-dimensional (2D) beam scanning lasers are in high demand for various applications including sensing systems for smart mobility, object recognition systems, and adaptive illuminations. Here, we propose and demonstrate the concept of dually modulated photonic crystals to realize such lasers, wherein the positions and sizes of the photonic-crystal lattice points are modulated simultaneously. We show using nano-antenna theory that this photonic nano

We present a new method to characterize thin-film electro-optic materials. The method is based on resolving the electric and/or magnetic field distributions in the near-field region of a split-ring resonator (SRR) designed for the terahertz (THz) frequency range. We experimentally validate our simulations by THz near-field imaging of SRRs directly patterned in contact with a thin-film lithium niobate crystal as a sensor. Furthermore, we analytically study the effect of the different applied elec

Photonic-crystal surface-emitting lasers (PCSELs) with modulated photonic crystals have attracted much attention for their unrivaled capabilities, such as broad area coherent resonance, and lens-free beam scanning and flash illumination. In this paper, we first explain the principles and the development of PCSELs with modulated photonic crystals toward non-mechanical two-dimensional (2D) beam-scanning applications. Then, we show PCSELs with modulated photonic crystals, whose modulation is design

Flash light sources with a wide field of view (FOV) are indispensable in various fields such as light detection and ranging (LiDAR), optical wireless communication, and adaptive lighting. However, conventional flash light sources, which combine lasers with external optical elements, tend to suffer from high complexity, large size, and high cost. In this study, we investigate a new wide-FOV flash light source which does not require external optical elements, based on a dually modulated photonic c

Dually modulated photonic-crystal surface-emitting lasers (DM-PCSELs) are a new type of semiconductor laser that enable on-chip, mechanical-free, high-power, high-beam-quality 2D beam scanning over a wide field of view. These lasers are attracting attention for application in light detection and ranging, and the improvement of their slope efficiency is desired for this application. Thus far, the highest experimentally demonstrated slope efficiency is approximately 0.4 W/A at wavelengths of aroun

We propose modulated PCSELs (M-PCSELs) with a double lattice and a Q-switching mechanism for emitting structured light. A 28-dot pattern with a peak power of >5W is successfully generated at a current injection of ~1A, where the pulse width is <100ps and each dot has a narrow divergence angle of <0.5°.

Compact, high-peak-power light sources emitting structured light such as multi-dot patterns are desired for face recognition and light detection and ranging (LiDAR) applications, especially in the field of mobile technology. Conventionally, such light sources are composed of VCSEL arrays, lenses, and diffractive optical elements (DOEs), resulting in large and complex systems. To address these issues, we propose and introduce double-lattice structures and saturable absorbers to modulated photonic

Mechanical-free, high-power, high-beam quality two-dimensional beam scanning is strongly required for LiDAR systems for autonomous driving. Here, we propose and demonstrate a new, dually-modulated photonic crystal laser, with which we successfully emit a high-quality laser beam with watt-class power in any desired direction.