Owing to its high-speed, selective, non-linear, contactless, and quantum characteristics, light has the potential to produce new functionality and a new technological paradigm, when combined with novel materials. This article reviews the frontier of research concerning the study of the interaction between light and ordered spins (magnetization) in the form of ultra-short light pulses and magnetic materials. A personal perspective as to new applications in the field of information processing and transmission is also discussed in view of photonics materials.

Inherent technical problems in solution processing, including printing, which we encounter in fabricating electronic devices by solution processing, are presented first, in the order of the device production steps and then general approaches as to how they can be handled are described together with a clarification of the causes of problems. Next, several case studies that have solved actual problems are presented, taking the solution processes using liquid silicon and metal oxide materials as examples. With regard to the topic of device printing, nano-rheology printing, which guarantees more precise printing than conventional approaches, is introduced as an example of a solution to the inherent issues of device printing technology.

The terahertz (THz) frequency range creates possibilities for various applications, such as imaging and high-speed wireless communications. For these applications, the source is a key component. Resonant tunneling diodes (RTDs) are expected to be a candidate for compact THz sources with semiconductors. Presently, a room-temperature oscillation at 1.42 THz has been achieved by reducing the electron delay time, and a high output power has been obtained with improved antennas and array configurations. Preliminary experiments on wireless communications and imaging have recently also been started. In this article, progress on the study of RTD oscillators, as they approach high-frequency and high-power operations, as well as progress on various properties for different applications are introduced.

Quantitative evaluations of the spin torque switching current and the thermal stability of a magnetic tunnel junction are greatly desired to realize Spintronics devices. To meet this requirement, a theory of spin torque switching should be established. However, it is a difficult problem from the viewpoint of the fundamental physics because spin torque is a non-conservative force. Recently, there have been great advances in overcoming this difficulty, and it has become possible to compare theory with experimental results. Also, it has been pointed out that the validity of the previously evaluated values of the switching current and the thermal stability may be low. These developments in the theory will enable us to put Spintronics devices into practical use. In this paper, a summary of the latest theory is presented.

Research on THz communications applications has become very active with several study groups on THz communication across the globe discussing issues regarding enabling technologies, system applications, standardization, etc. In this paper, we describe recent progress in THz communications technologies based on photonics and electronics, and discuss future prospects.

Ultrathin magnetic heterostructures are attracting great interest recently as new phenomena and novel physics related to spin orbit coupling have been revealed. Manipulating magnetic moments with an electrical current plays an essential role in Spintronics. To date, spin polarized current and spin transfer torque have been used to control the direction of magnetic moments. New paradigms for current controlled magnetism have been made possible recently by the introduction of materials or film structures with a large spin orbit coupling. In this article, I will discuss recent developments in current driven domain wall motion in nanowires made of ultrathin magnetic heterostructures. With the spin Hall effect and the anti-symmetric exchange interaction known as the Dzyaloshinskii-Moriya interaction, an unconventional mechanism for current driven domain wall motion is described: the direction to which a domain wall moves with current and its velocity can now be tuned by the materials and stacking of the heterostructure.

Glass-ceramics (GCs) are polycrystals obtained by crystallization of the functional phase in precursor glass. Because the crystallized phase and its morphology are controllable, the GC processing is effective for creating the advanced functional materials. Recently, our research group has demonstrated “perfect surface crystallization (PSC)” in non-stoichiometric precursor glass. The PSC refers to the formation of a uniform/dense crystalline texture, in which the crystal domains grow from the glass surfaces, and eventually their growth fronts impinge on each other. We found that the PSC-GCs consisting of a polar fresnoite phase possess a strong orientation, and also demonstrate an excellent optical transmittance and optical switching/modulation function that is comparable to that of an optical single crystal.

Recently, fiber lasers emanating femtosecond pulses at 1.5µm have been replacing the Ti:S lasers that were used for the generation and detection of THz waves in commercial time domain spectroscopy systems. To make the replacement efficient, it is necessary to develop a good photoconductive antenna that is excitable at 1.5µm. Though InGaAs-based antennas have been investigated and are commercially available now, the rather high noise level hampers the realization of a high signal-to-noise ratio. On the other hand, the excitation efficiency of low-temperature-grown (LTG) GaAs, which is suited for Ti:S lasers, is insufficient at 1.5µm. However, since the noise level of LTG GaAs antennas is very low, it can be an efficient antenna even for 1.5µm pulses, if one can improve its responsivity. One of the ways to accomplish this is to take advantage of the nonlinear absorption. In this article, we present our recent research on the excitation of LTG GaAs at 1.5µm.