National Institute of Advanced Industrial Science and Technology

Vadym Zayets

Koji Ando

Shinji Yuasa

Hidekazu Saito

An optical device having a plasmonic waveguide, in which the plasmonic waveguide has a layered structure of at least three layers that a ferromagnetic metal layer, a first dielectric layer, and a second dielectric layer are layered in this order, in which the first and second dielectric layers are layers that allow light to be transmitted therethrough, and in which a refractive index of the second dielectric layer is higher than a refractive index of the first dielectric layer; and an optical isolator, having the optical device.

Optical device using a plasmonic waveguide, and optical isolator

A nonvolatile optical memory element in which a ferromagnetic body is provided on a semiconductor causes such a problem that in a case where magnetization of the ferromagnetic body is read by light, magneto-optical response becomes very small when the ferromagnetic body is small in volume. The present invention provides a memory element, a memory device, and a data reading method, each of which is applicable to data reading from a nonvolatile optical memory element. In a nonvolatile optical memory element having a structure in which a ferromagnetic body is provided on a semiconductor that is connected to an optical waveguide, electrons are injected into the semiconductor via the ferromagnetic body so that the electrons that are spin-polarized according to a magnetization direction of the ferromagnetic body are injected into the semiconductor, thereby enlarging a region in which a photomagnetic effect occurs effectively. By applying an electric pulse and an optical pulse to the nonvolatile optical memory element, it is possible to effectively read recorded data according to a magnetization direction of the ferromagnetic body.

Nonvolatile optical memory element, memory device, and reading method thereof

A very small magnetic tunnel junction is formed on a semiconductor p-i-n diode. Spin-polarized current which is generated by circular polarized light or elliptically-polarized light, is injected into a free layer of the magnetic tunnel junction so that magnetization direction (two opposite directions) in the free layer is changed based on the information, whereby information is stored in the memory element.

Non-volatile memory element and method of operation therefor

The present invention relates to a high-speed optical memory element. In order to increase speed of a memory element, optical pulse is recorded and read all-optically without conversion into electrical signal at very high speed. Optically-induced spin accumulation is used for recording the ferromagnetic metal embedded into optical waveguide operates as a high speed memory element. The ferromagnetic metal is sandwiched between a conductor on one side and a tunnel barrier followed by a conductor on the other side. The voltage is applied between two conductors. For data recording, the optically induced spin-polarized tunneling and spin accumulation is used. The optically induced spin-polarized tunneling occurs due to absorption of circularly polarized light. The torque of accumulated spin reverses magnetization of ferromagnetic metal. For reading Faraday rotation or non-reciprocal loss/gain in semiconductor-ferromagnetic-metal hybrid is used.

Growing community of inventors

Ibaraki, Japan

Vadym Zayets