Daisuke Inoue

We proposed and demonstrated a novel three-dimensional (3D) scanning image sensor consisting of a lens and chip with a detection range of 204 m and 3D imaging of a building located 45 m away.

Imaging optics cannot focus light beams emitted from different points onto one point with a lens. Therefore, fabricating a 3D image sensor with a focal plane array is challenging. We developed an imaging optics device with an intentionally shifted focal plane switch array comprising pixels with two optical antennas, a switch, and a receiver on a chip. We successfully illuminated a single point, received the reflected light with the same pixel, and scanned an illuminating target. The proposed system can serve as a 3D image sensor, with a detection range of 204 m for Lambertian reflectors with 94% reflectivity, and as a beam combiner for high-power lasers.

We developed a light detection and ranging (LliDAR) system with a coin-sized sensor head, which includes a scanning mechanism. This powerful detection device, which incorporates optical fiber, is based on time-of-flight measurements and can detect targets up to a distance of 200 m. The main characteristic of our system is the utilization of optical amplifiers for the receiver. This enabled the system to exceed the detection limit set by the thermal noise and reach the detection limit set by the shot noise. We demonstrated a 200 m measurement range, for a receiving lens of only 3 mm in diameter. This small and highly sensitive measurement technology can potentially be used in automotive lidarLiDAR.

Grating couplers (GCs) are devices for transmitting and receiving the light propagated in a waveguide in silicon photonic integrated circuits (PICs). In this study, we propose a polarization splitting GC (PSGC) for the optical antenna of light detection and ranging (LiDAR). The PSGC was designed on the basis of two GCs coupling in a perfectly vertical direction. Our experiment demonstrated that the designed PSGC transmitted a polarization-multiplexed beam. The transmitting and receiving efficiencies of the optical antenna consists of lenses and PSGCs were calculated, and then the optical parameter for maximizing them was clarified.

This paper presents physical-layer cell identity (PCID) detection probability using synchronization signals for the 5G New Radio (NR) initial access in 3rd generation partnership project (3GPP) tapped delay line (TDL) channel models. Computer simulation results validate the PCID detection probability based on the cumulative distribution of the instantaneous received power level of the synchronization signal for the respective channel models. We also show that the high PCID detection probability is achieved by using the NR synchronization signals in the 3GPP TDL channel models.

We have developed a novel phase modulator, based on fin-type electrodes placed at self-imaging positions of a silicon multimode interference (MMI) waveguide, which allows reduced scattering losses and relaxes the fabrication tolerance. The measured propagation losses and spectral bandwidth are 0.7 dB and 33 nm, respectively, on a 987 μm-long phase shifter. Owing to the self-imaging effect in the MMI waveguide, the wave-front expansion to the electrode was counteracted, and therefore, the scattering loss caused by electrode fins was successfully mitigated. As a proof-of-concept for the MMI-based phase modulator applications, we performed optical modulation based on Mach–Zehnder interferometers (MZIs). The π shift current of the modulator was 1.5 mA.

The reliability and small size of solid state scanners makes them ideal for LIDAR. We fabricated and demonstrated the successful operation of an optical scanner using silicon photonics integrated circuit technology. The scanner comprises a ring resonator multiplexer and a number of grating arrays, and employs a beam switching method, which means that the scanner is movement-free. The multiplexer determines the optical path and light is emitted from the selected grating. The scanning angle obtained was 6 degrees. LIDAR sensors can be used in automotive applications for automated cruising.

We propose two-photon absorption light-induced self-written (LISW) waveguide formation using short-wavelength infrared pulse laser light. It is suitable and efficient for single-mode optical interconnection, and also promising for small-core single-mode optical interconnection. The approach offers the possibility of not only decreasing the insertion loss, but also reducing the interconnection task time. We assessed this approach for single-mode optical interconnection. We obtained an LISW waveguide loss of about 0.06 dB for an LISW waveguide length of 100 μ m and a connection loss per facet of about 0.37 dB. We also presented the results on the interconnection between high-numerical-aperture small-core thermally-diffused expanded-core single-mode fibers having the mode field diameters of about 3 μm by using the same approach. The results showed the present approach to be a promising alternative route for efficient interconnection of small-core single-mode optical devices, such as silicon nanowires with appropriate configurations.

We fabricated arrays of subwavelength slits in an Al film and measured their optical properties in the visible light region. Al crossbeams were installed as supports between the Al lines to enable us to precisely fabricate the nanoslits. Visible light polarized parallel to the slits transmits at shorter wavelengths, similar to that of a wire grid array at infrared wavelengths. On the other hand, for light polarized perpendicular to the slits, the transmission is at longer wavelengths and significant absorption takes place at shorter wavelengths due to Fano-type interference. This absorption in the visible wavelength region is due to the precise nanofabrication process and the high plasma frequency of Al. These results show that Al nanoslits can be used as polarization filters in the visible wavelength region.