Graphene and related two-dimensional materials are attracting intense attention as materials that will revolutionize our society and lives. There are a wide variety of two-dimensional materials from metals, semiconductors, to insulators, and they have the common characteristics of transparency and flexibility. Therefore, two-dimensional materials and their heterostructures are expected to be applied to a very large range of applications such as electronics, photonics, sensing, energy storage and conversion, biotechnology, and composite materials. In this paper, we review the current status of two-dimensional materials with an emphasis on the crystal growth of graphene.

The vertical cavity surface emitting laser (VCSEL) was born in Japan. The 38 years of research and development has opened up various applications including data communication, sensors, optical interconnections, spectroscopy, optical storage, printers, laser displays, laser radar, atomic clocks and high power sources. A lot of unique features have been already proven, such as low power consumption, wafer level testing and so on. The market for VCSELs has been maturing rapidly and they are now key devices in local area networks, and optical interconnections in data centers and supercomputers.

In this paper, the advances in VCSEL photonics will be reviewed. We present the high-speed modulation of VCSELs based on a coupled cavity structure. For further increase in transmission capacity per fiber, the wavelength engineering of VCSEL arrays is discussed, which includes wavelength stabilization and wavelength tuning based on a micro-machined cantilever structure. We also address a lateral integration platform and new functions, including high-resolution beam scanners, vortex beam creation and large-port free space wavelength selective switches with a Bragg reflector waveguide.

The nervous system processes huge amounts of information autonomously with extremely low power. It has a highly parallel structure where the electrical activities of neuronal cells are transmitted to each other by synapses. Silicon neuronal networks are a bottom-up approach to reproduce such electrical activities by connecting silicon neuron circuits by synapses. It is thought to be a major candidate for the next generation of information processing system. However, to establish the fundamental technology, we have to solve a difficult problem: the elucidation of the information processing architecture in the nervous system. In this article, we provide a brief overview of our efforts and perspectives to approach this goal.

Phase change random access memory (PRAM) consisting of a superlattice of GeTe and Sb₂Te₃ has recently become attractive, not only from the viewpoint of the remarkable switching energy suppression, but also from the topological properties of the electronic structure. The spatial inversion symmetry and time reversal symmetry of a superlattice can be broken by an external electric or magnetic field, and both the initial structure (RESET) and the broken structure (SET) are energetically stable phases as a result of the structural phase transition. This unique feature may induce unusual magnetic properties to the superlattice, such as giant magnetoresistance and mirror-symmetric magneto-optical Kerr rotation. It may open a new door to spintronics devices in the future.

Based on ab initio calculations using density functional theory, we theoretically proposed possible geometric structures of magnetic carbon nanotubes. By cutting the zigzag CNT, the finite CNTs exhibit several magnetic states depending on their diameter. In addition, topological line defects in CNTs also lead to ferromagnetic spin ordering along the defects. Our detailed analysis of the electronic structure of finite-length CNTs and defective CNTs unraveled that the spin polarization is induced by the edge localized states of a graphene nanoribbon with zigzag edges.

One can observe terahertz (THz) radiation from various kinds of materials and devices, when excited with a femtosecond laser, owing to ultrafast current modulation, which reflects ultrafast transient phenomena in optically excited ones. By scanning the laser beam on them, THz emission images are obtained with a resolution of approximately the laser beam diameter rather than the THz wavelength. Thus the construction of a laser-THz emission microscope (LTEM) can provide a new tool for material/device science and applications. We proposed and have been developing an LTEM since 1997. Here we report on the recent progress of LTEM development, a dynamic LTEM, a near field LTEM, and some examples such as the noncontact localization of a LSI failure, the evaluation of solar cells, and the imaging of the surface potential of GaN wafers.

Today, in the 21^st Century, control systems are essential for experiments with electronic devices. Getting accustomed to the methods of input/output information with computer, a wide variety of applications can be realized such as systems that obtain enormous amounts of test data on an ongoing basis, or live demonstrations that astonish audiences. Free or with fees, various types of control “systems” have become available and they are constantly improving. However, as long as the author understands the “basic concept of input/output,” there is no need to fear the tide of the times. This article introduces the basic concepts of control systems so that the reader can have a clear image in mind.