Nippon Telegraph and Telephone Corporation

Kengo Nozaki

Masaya Notomi

Akihiko Shinya

Shota Kita

Kenta Takata

Masaaki Ono

Eiichi Kuramochi

Masato Takiguchi

Katsumasa Yoshioka

The output computing unit includes cascade-connected N number of Y coupling elements having two inputs and one output, and N number of optical intensity modulators. The N number of light intensity modulators individually modulate the intensity of a continuous light to a second optical input port, which is different from a first optical input port to which no light is input or to which a signal light from an optical output port of a Y coupling element in a previous stage, out of two optical input ports of each of the cascade-connected N number of Y coupling elements, in accordance with corresponding bits of an N-bit electric digital signal. The output light acquired from the Y coupling element 1-N in the final stage is regarded as the N-bit digital analog computing result.

Optical arithmetic unit

A photodetector includes a substrate, a material layer, a first electrode made of a metal, a core, a second electrode and a light absorption layer made of graphene. The first electrode, the core, and the material layer constitute a hybrid plasmonic waveguide, and the light absorption layer is disposed thereon. Light guided in the hybrid plasmonic waveguide is absorbed by the light absorption layer, photoelectrically converted by the PTE effect, and extracted as an electric signal from the first electrode and the second electrode.

Photo-detector

An optical DAC includes a 1:N splitter that splits a single light beam into N light beams corresponding to bits of an N-bit electrical digital signal (where N is an integer of 2 or more) and makes the N light beams different in optical intensities such that (N−1) light beams corresponding to bits except a least significant bit of the N-bit electrical digital signal each have an optical intensity which is four times as large as an optical intensity of a light beam corresponding to a next less significant bit, an optical intensity modulator that individually intensity-modulates the N light beams, an N:1 combiner that combines the N output light beams intensity-modulated by the optical intensity modulator and outputs the combined light, and a phase shifter that is adjustable such that the light beams that are combined by the N:1 combiner are made in phase.

Optical digital/analog converter

An optical IQ modulator includes: Y branching elements, which are cascade-connected, each of which has one input and two outputs; QPSK modulators configured to perform QPSK modulation on continuous light branched by the Y branching elements to generate signal light; and Y combining elements, which are cascade-connected, each of which has two inputs and one output.

Optical IQ modulator

The amount of outward shift of a lattice element () and a lattice element (), the outward shift being symmetrical with respect to a resonator center on a straight line, is 0.42 to 0.5 times a lattice constant of a photonic crystal. The amount of outward shift of a lattice element () and a lattice element (), the outward shift being symmetrical with respect to the resonator center on the straight line, is 0.26 to 0.38 times the lattice constant of the photonic crystal. The amount of outward shift of a lattice element () and a lattice element (), the outward shift being symmetrical with respect to the resonator center on the straight line, is 0.13 to 0.19 times the lattice constant of the photonic crystal. The amount of outward shift of a lattice element () and a lattice element (), the outward shift being symmetrical with respect to the resonator center on the straight line, is &#x2212;0.1 to 0 times the lattice constant of the photonic crystal.

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Tokyo, Japan

Kengo Nozaki