Abstract: A parallel computer system includes: direct links that forms a direct connection between a sending node and a receiving node, one-hop links that forms a connection between a sending node and a receiving node by way of a return node that is other than the sending node and the receiving node, and a communication control unit that, when transferring data from a sending node to a receiving node, selects the link that connects the sending node and the receiving node from among a link that uses only a direct link, a link that uses only a one-hop link, and a link that forms a connection combines and uses the direct link and the one-hop link.

Abstract: An optical transmitter-receiver includes an optical integrated device in which at least an optical modulator and an optical detector are integrated as optical devices over the same substrate and an insulating layer is provided between the optical modulator and the substrate and between the optical detector and the substrate, and an electronic circuit chip that is connected to the optical integrated device and includes an electronic circuit including a ground wiring line. The optical integrated device includes a shield electrode between the optical modulator and the optical detector, and the shield electrode is provided sandwiching the insulating layer with the substrate to configure a capacitance and is connected to the ground wiring line of the electronic circuit chip.

Abstract: An optical transmitter-receiver includes an optical integrated device in which at least an optical modulator and an optical detector are integrated as optical devices over the same substrate and an insulating layer is provided between the optical modulator and the substrate and between the optical detector and the substrate, and an electronic circuit chip that is connected to the optical integrated device and includes an electronic circuit including a ground wiring line. The optical integrated device includes a shield electrode between the optical modulator and the optical detector, and the shield electrode is provided sandwiching the insulating layer with the substrate to configure a capacitance and is connected to the ground wiring line of the electronic circuit chip.

Abstract: A parallel computer system includes: direct links that forms a direct connection between a sending node and a receiving node, one-hop links that forms a connection between a sending node and a receiving node by way of a return node that is other than the sending node and the receiving node, and a communication control unit that, when transferring data from a sending node to a receiving node, selects the link that connects the sending node and the receiving node from among a link that uses only a direct link, a link that uses only a one-hop link, and a link that forms a connection combines and uses the direct link and the one-hop link.

Abstract: An optical transmitter includes: a driving circuit that includes drivers each corresponding to a configuration bit of an input electrical data sequence; a MZ optical modulator that includes a first phase shifter provided in an arm and a second phase shifter provided in an arm; first capacitance elements that are electrically connected between the driving unit and the first phase shifter, each include an electric capacity weighted in response to a bit number of the configuration bit, and generate a first multilevel signal to be supplied to the first phase shifter; and second capacitance elements that are electrically connected between the driving circuit and the second phase shifter, each include an electric capacity weighted in response to a bit number of the configuration bit, and generate a second multilevel signal to be supplied to the second phase shifter.

Abstract: An optical transmitter includes: a driving circuit that includes drivers each corresponding to a configuration bit of an input electrical data sequence; a MZ optical modulator that includes a first phase shifter provided in an arm and a second phase shifter provided in an arm; first capacitance elements that are electrically connected between the driving unit and the first phase shifter, each include an electric capacity weighted in response to a bit number of the configuration bit, and generate a first multilevel signal to be supplied to the first phase shifter; and second capacitance elements that are electrically connected between the driving circuit and the second phase shifter, each include an electric capacity weighted in response to a bit number of the configuration bit, and generate a second multilevel signal to be supplied to the second phase shifter.

Abstract: An optical modulation device includes: an optical waveguide formed above a substrate; a phase modulator disposed on part of the optical waveguide; a capacitor connected to the phase modulator and including a lower electrode and an upper electrode; a resistor connected in parallel to the capacitor; and an appended part integrated with the upper electrode and electrically connected to the resistor, wherein the appended part is smaller in area than the capacitor (upper electrode).

Abstract: An optical modulation device includes: an optical waveguide formed above a substrate; a phase modulator disposed on part of the optical waveguide; a capacitor connected to the phase modulator and including a lower electrode and an upper electrode; a resistor connected in parallel to the capacitor; and an appended part integrated with the upper electrode and electrically connected to the resistor, wherein the appended part is smaller in area than the capacitor (upper electrode).

Abstract: An optical receiver circuit has a function of converting a differential optical signal into a differential current signal. The optical receiver circuit has a pair of light-receiving elements including first and second light-receiving elements operable to convert an optical signal into a current signal and a pair of signal lines. An anode of the first light-receiving element and a cathode of the second light-receiving element are connected to a first signal line of the pair of signal lines via first and second AC coupling capacitors, respectively. A cathode of the first light-receiving element and an anode of the second light-receiving element are connected to a second signal line of the pair of signal lines via third and fourth AC coupling capacitors, respectively. Differential signal currents are generated in the first and second signal lines in response to reception of differential optical signals inputted into the first and second light-receiving elements.

Abstract: An opto-electric integrated circuit includes an optical waveguide formed using a portion of an insulation layer on a silicon substrate to form a lower clad and using a portion of a semiconductor layer formed on the insulation layer to form a core. The opto-electric integrated circuit also includes an optical device connected to the optical waveguide, an electrical circuit connected to the optical device, a mesa-shaped connection section interconnecting the optical device and the electrical circuit, and an electrically conductive film formed in a region at least containing a flank surface of the connection section. The electrically conductive film is grounded while contacting the silicon substrate.

Abstract: An optical semiconductor device includes: an electric-optic conversion element that is provided with a diode; and a driving circuit that drives the diode in a forward direction, the driving circuit including a first switching circuit that is provided with a first switch, and a second switching circuit that is provided with a second switch, wherein the first switching circuit constitutes a first signal line that charges the electric-optic conversion element with an electric charge by bringing the first switch into an ON state and the second switch into an OFF state, and the second switching circuit constitutes a second signal line that discharges the electric charge stored in the electric-optic conversion element by bringing the second switch into an ON state and the first switch into an OFF state.

Abstract: An optical receiver circuit has a function of converting a differential optical signal into a differential current signal. The optical receiver circuit has a pair of light-receiving elements including first and second light-receiving elements operable to convert an optical signal into a current signal and a pair of signal lines. An anode of the first light-receiving element and a cathode of the second light-receiving element are connected to a first signal line of the pair of signal lines via first and second AC coupling capacitors, respectively. A cathode of the first light-receiving element and an anode of the second light-receiving element are connected to a second signal line of the pair of signal lines via third and fourth AC coupling capacitors, respectively. Differential signal currents are generated in the first and second signal lines in response to reception of differential optical signals inputted into the first and second light-receiving elements.

Abstract: An optical semiconductor device includes: an electric-optic conversion element that is provided with a diode; and a driving circuit that drives the diode in a forward direction, the driving circuit including a first switching circuit that is provided with a first switch, and a second switching circuit that is provided with a second switch, wherein the first switching circuit constitutes a first signal line that charges the electric-optic conversion element with an electric charge by bringing the first switch into an ON state and the second switch into an OFF state, and the second switching circuit constitutes a second signal line that discharges the electric charge stored in the electric-optic conversion element by bringing the second switch into an ON state and the first switch into an OFF state.

Abstract: An opto-electric integrated circuit includes an optical waveguide formed using a portion of an insulation layer on a silicon substrate to form a lower clad and using a portion of a semiconductor layer formed on the insulation layer to form a core. The opto-electric integrated circuit also includes an optical device connected to the optical waveguide, an electrical circuit connected to the optical device, a mesa-shaped connection section interconnecting the optical device and the electrical circuit, and an electrically conductive film formed in a region at least containing a flank surface of the connection section. The electrically conductive film is grounded while contacting the silicon substrate.

Abstract: There is provided a transmission apparatus which includes a transmitting circuit that receives a bit string in which an input bit string expressed as combination of 0 and 1 is preceded by a 1-bit value 0, computes a difference value between two bits adjacent to each other in the bit string, the difference value being one of among +1, 0, or ?1, and sends the computed difference value, and a receiving circuit that stores a 1-bit value with an initial value of 0, receives the difference value +1, 0, or ?1 sent by the transmitting circuit, calculates a sum of the received difference value and the stored 1-bit value, outputs, as a value of a receiving signal, 1 if the sum is 1 or more or 0 if the sum is 0 or less, and updates the stored 1-bit value to the value of the output receiving signals.

Abstract: A private key delivery system and a private key delivery method are disclosed. The private key delivery system includes a transmitter, a receiver, and an optical transmission line connecting the transmitter and the receiver. The transmitter includes a single photon generating unit for simultaneously generating two or more single photons having different wavelengths using a quantum dot structure that has quantum dots of various sizes, an optical splitter for splitting the single photons by wavelengths, a phase modulating unit for modulating each of the single photons split by the wavelengths with private key information, and an optical multiplexer for multiplexing the modulated single photons of the different wavelength and for transmitting the multiplexed single photons to the optical transmission line. The multiplexed single photons are received by the receiver, and the private key information is taken out from the received single photons.

Abstract: By bringing a tip of an AFM into contact with the surface of a GaAs substrate or an AlGaAs substrate, for example, applying a negative bias to the tip, and applying a positive bias to the GaAs substrate or the AlGaAs substrate, a donut-shaped oxide film is formed. Then, the oxide film is removed. As a result, a ring-shaped groove is formed in the surface of the GaAs substrate or the AlGaAs substrate. The oxide film can be removed by chemical etching, ultrasonic cleaning with water, a treatment with atomic hydrogen in a vacuum, or the like. Thereafter, a semiconductor film (InAs film or InGaAs film, for example) is epitaxially grown in the groove. Then, a capping layer which covers the semiconductor film and the GaAs substrate or the AlGaAs substrate is formed.

Abstract: A single-photon generator includes a single-photon generating device generating a single-photon pulse having a wavelength on the shorter wavelength side than a communication wavelength band, and a single-photon wavelength conversion device performing wavelength conversion of the single-photon pulse into a single-photon pulse of the communication wavelength band, using pump pulse light for single-photon wavelength conversion.

Abstract: A single-photon generating device is configured to have a solid substrate including abase portion, and a pillar portion which is formed on the surface side of the base portion with a localized level existent in the vicinity of the tip of the base portion. The above pillar portion is formed to have a larger cross section on the base portion side than the cross section on the tip side, so that the light generated from the localized level is reflected on the surface, propagated inside the pillar portion, and output from the back face side of the base portion.

Abstract: Provided is an optical semiconductor device, which includes a GaAs substrate (or a semiconductor substrate) 20; an n-type contact layer (or a doping layer) 21 formed on one surface 20a of the GaAs substrate 20; an active layer 25 formed on top of the n-type contact layer 21 and including at least one quantum dot 23; a p-type contact layer (or a contact layer) 26 formed on top of the active layer 25 and being of an opposite conduction type to the n-type contact layer 21; an insulating layer 29 formed on top of the p-type contact layer 26 and including a first opening 29a whose size is such that a contact region CR of the p-type contact layer 26 lies within the first opening 29a; a p-side electrode layer 33c formed on top of the contact region CR of the p-type contact layer 26 and on top of the insulating layer 29 and including a second opening 33a lying within the first opening 29a; and a n-side electrode layer (or a second electrode layer) 37 formed on the other surface 20b of the GaAs substrate 20.