The University of Tokyo · Physics and Astronomy
Professor Shinji Yamashita's research lab specializes in the development and application of low-dimensional carbon nanomaterials, particularly carbon nanotubes and graphene, for advanced photonic and optoelectronic devices. The lab focuses on exploiting the unique nonlinear optical properties of these materials—such as saturable absorption—for ultrafast fiber laser systems, including mode-locked lasers generating subpicosecond pulses. They also investigate novel 1D and 2D materials for next-generation functional devices, including electro-optic modulators and multiwavelength light sources for optical communication. Additionally, the lab explores the growth and magnetic properties of thin-film materials for potential use in compact, high-performance magnetic devices.
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We present novel carbon-nanotube-based saturable absorbers. Using the low-temperature alcohol catalytic chemical-vapor deposition method, high-quality single-walled carbon nanotubes (SWNTs) were directly synthesized on quartz substrates and fiber ends. We successfully applied the SWNTs to mode lock a fiber laser producing subpicosecond pulses at a 50-MHz repetition rate.
One and two dimensional forms of carbon, Carbon nanotube and graphene, have interesting and useful not only electronic but also photonic properties. This tutorial will review their photonic properties, linear and nonlinear, and applications of nonlinear photonic properties as laser mode lockers and nonlinear functional devices.
The authors report simultaneous oscillation of 17 0.8 nm spaced wavelengths from a Fabry-Perot (FP) erbium doped fibre laser. Multiwavelength operation is made possible by inserting an intracavity etalon and cooling the erbium doped fibre at 77 K by liquid nitrogen. It is promising as the multiwavelength light source for wavelength division multiplexing (WDM) networks. Heterodyne measurement shows that two or three longitudinal modes exist in each wavelength.
One- and two-dimensional forms of carbon, carbon nanotube, and graphene, and related 2D materials, have attracted great attention of researchers in many fields for their interesting and useful electrical, optical, chemical, and mechanical properties. In this tutorial, we will introduce the basic physics and the linear optical properties of these 1D/2D materials. We then focus on their nonlinear optical properties, saturable absorption, electro-optic effect, and nonlinear Kerr effect. We will als
Efforts were made to obtain anisotropic thin-film magnets at low substrate temperature. This is an important criterion for practical applications such as to build motors. The influence of substrate materials as well as film thickness on the c-axis orientation were studied. It has been shown that thin-film magnets with the easy axis of magnetization normal to the film plane could be deposited at a substrate temperature of around 450 °C by choosing the composition near the line from Nd13Fe76B11 to
We demonstrate passive mode-locking of a short-cavity (/spl sim/2 cm) fiber Fabry-Pe/spl acute/rot laser by incorporating a carbon-nanotube-based saturable absorber. Stable pulses are generated with a pulsewidth as short as 0.68 ps at a repetition rate as high as 5.18 GHz. This is the smallest femtosecond fiber pulsed laser ever demonstrated to date.
We demonstrate a wide and fast wavelength-tunable modelocked fiber laser based on tuning the mode-locking frequency. The laser is in a sigma-laser configuration, and a wideband semiconductor optical amplifier (SOA) at 1.3 mum wavelength region is used as a gain medium. Mode locking is achieved by direct modulation of the injection current to the SOA, and a dispersion compensation fiber (DCF) is used to provide desired intracavity dispersion. By tuning the modulation frequency, a wide tuning rang
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