Overview of Research in Laboratories

Materials Science Laboratory
Hideki Yamamoto
   The aim of the Materials Science Laboratory is to contribute to progress in materials science and to revolutionize information communication technology by creating novel materials and functions through materials design at the atomic and molecular levels.
   The laboratory consists of three research groups investigating a wide range of materials e.g., typical compound semiconductors including GaAs and GaN, two-dimensional materials such as graphene, high-Tc oxide superconductors, and biological molecules. We are conducting innovative materials research based on advanced thin-film growth technologies along with high-precision and high-resolution measurements of structures and properties.
   This year, we succeeded in growing high-quality N-polar GaN, metastable c-BN, and as-grown superconducting thin films. We also applied controlled strain to graphene, which provides way of realizing “graphene strain engineering”. Moreover, we successfully measured mental and physical bio-signals in various use scenarios including medical, rehabilitation, sports, worker safety control and extreme situations by using a functional sensing fabric “hitoe®”, which we developed in collaboration with Toray Industries, Inc.
Physical Science Laboratory
Akira Fujiwara
   The aim of the Physical Science Laboratory is to develop semiconductor- and superconductor-based devices and/or hybrid-type devices, which will have a revolutionary impact on future ICT society. Utilizing the high-quality crystal growth techniques and nanolithography techniques that we have developed, research groups in our laboratory are exploring novel properties that can lead to nanodevices for ultimate electronics and novel information processing devices based on new degrees of freedom such as single electrons, mechanical oscillations, quantum coherent states, electron correlation, and spins.
   This year we succeeded in realizing optomechanical system using excitonic transitions in semiconductor heterostructures and an electron beam splitter at a graphene p-n junction in the quantum Hall regime. We also demonstrated experimentally the operation of a MoS2/SiO2/Si tunnel diode, thermal-noise suppression by feedback control of single electrons in Si nanotransistors, and gate-controlled semimetal-topological insulator transition in InAs/GaSb heterostructures. We show theoretically that the spin coherence time of an NV center in diamond can be significantly improved by coupling it to a superconducting flux qubit.
Optical Science Laboratory
Hideki Gotoh
   The aims of the Optical Science Laboratory are to develop innovative core technologies for optical communications and optical signal processing, and to make fundamental scientific progress.
The groups in our laboratory are working to achieve quantum state control and quantum information processing by using very weak light, to discover intriguing phenomena by using very intense short pulse light, to control optical properties by using photonic crystals and ultrasonic techniques, and to characterize the unique properties of semiconductor nanostructures such as quantum dots and nanowires.
   This year, one of our achievements in quantum information processing has been the demonstration of a new scheme for manipulating the color of single phonons, which are the main carriers of information. Moreover, we have proposed an uncrackable quantum cryptography technique for use over double the previous distance and developed a new quantum cryptography scheme that can ensure security without us having to monitor the error rate of a photon transmission. In the spintronics field, we have achieved spin transportation over 100 mm in semiconductor nanostructures, which will be applied to spin functional devices in the near future.
Nanophotonics Center
Masaya Notomi
   The Nanophotonics Center (NPC) was established in April 2012, and is now composed of several groups involved in nanophotonics research and based in NTT’s Basic Research Laboratories and Device Integration Laboratories. Our aim is to develop a full-fledged large-scale photonic integration technology by which we will be able to densely integrate a large number of nano-scale photonic devices with various functions in a single chip. Furthermore, we are targeting a huge reduction in energy consumption for photonic information processing by taking advantage of nanophotonics technology.
   This year, we broke the power consumption record for photonic memories by one order of magnitude by using novel photonic crystal nanocavities, and demonstrated laser oscillation with a semiconductor nanowire on a silicon photonic crystal. In addition, we demonstrated thresholdless laser oscillation by using a special photonic crystal nanocavity, and realized distributed feedback membrane lasers on a silicon substrate with spot-size converters.