Abstract: The present invention is a laser system including a DFB laser 10 emitting a laser light 50, a semiconductor optical amplifier 20 that modulates an intensity of the laser light, and a harmonic generation element 30 that converts the laser light modulated to a visible light 54 that is a harmonic of the laser light. According to the present invention, it is possible to employ the highly efficient harmonic generation element capable of modulating the intensity of the laser light and to reduce power consumption.

Abstract: A semiconductor device including a semiconductor optical amplifier in which a photodetector is integrated without causing power loss at a low cost. The semiconductor device includes a semiconductor substrate, a semiconductor optical waveguide, at least partly capable of functioning as a semiconductor optical amplifier, to guide signal light, and a photodetector provided in a region other than a region where the semiconductor optical waveguide is provided, wherein the semiconductor optical waveguide and the photodetector are integrated on the semiconductor substrate.

Abstract: The present invention provides a semiconductor laser including a first conductive type of a lower clad layer 12, an active layer 14 provided on the lower clad layer 12, the active layer 14 including a plurality of quantum dots, and a second conductive type of an upper clad layer 18, the upper clad layer 18 being provided on the active layer 14 so as to have an isolated ridge portion 30 such that W1?Wtop+0.4 ?m where Wtop is the width of a top of the ridge portion 30 and W1 is the width of the ridge portion 30 at a height of 50 nm from a bottom of the ridge portion 30. The present invention also provides a method for manufacturing such a semiconductor laser.

Abstract: A detachable structure for an ink cartridge in a printer includes a storing unit, an acquisition unit, a determining unit, and an ink supply control unit. The storing unit is provided on the ink cartridge and stores information on the ink cartridge. The acquisition unit is provided on the printer and acquires the information stored in the storing unit when the ink cartridge is attached onto the printer. The determining unit certifies validity of the information acquired by the acquisition unit. The ink supply control unit allows ink supply from the ink cartridge when the validity of the information is certified by the determining unit. According to the structure, versatility of ink cartridges can be ensured and productivity cost for ink cartridges can be restricted. In addition, prevented can be undesirable ink mixture due to an erroneous installation of the ink cartridge by a user.

Abstract: A detachable structure for an ink cartridge includes a supply port, a joint section, an insertion rod and an anti-outflow member. The port is provided in the cartridge. The stopper is provided in the port and urged outward to close the port. The joint section is provided in a printer and coupled with the port. The joint section has an ink flow path that communicates with the port while the port is coupled. The insertion rod is provided in the joint section for pushing the stopper inward to communicate the ink flow path with the port while the port is coupled. The anti-outflow member is slidably provided in the joint section. The anti-outflow member is urged outward and slides along the insertion rod when the port is being inserted into the joint section. According to the structure, ink leakage on attaching or detaching of the cartridge can be prevented.

Abstract: On the upstream side of a quantum dot optical amplifier, a polarization beam splitter with one input and two outputs is provided. Two optical fibers connected to output sections of the polarization beam splitter are connected to input sections of the quantum dot optical amplifier in a state that both of the optical fibers have an electric field whose direction being adjusted to maximize its gain, and one optical fiber is twisted by 90.degree. to the other optical fiber. On the downstream side of the quantum dot optical amplifier, a polarization beam splitter with two inputs and one output is provided. Between two optical fibers connected to the polarization beam splitter, one is twisted by 90.degree. to the other. This twisting direction is reverse to the twisting direction of the two optical fibers connected to the input sections of the quantum dot optical amplifier.

Abstract: An optical transmission system includes an optical nonlinear element having nonlinear input/output characteristics, a power detector detecting a power of a specific frequency component related to an optical signal reproduced by the optical nonlinear element, and a variable amplifier amplifying or attenuating the optical signal inputted to the optical nonlinear element. Evaluation of an output waveform is performed based on the power of the specific frequency component detected by the power detector, and a gain of the variable amplifier is properly controlled, so that an input power of the optical signal inputted to the optical nonlinear element can be easily set such that a good output waveform can be obtained without directly measuring the inputted or outputted optical signal.

Abstract: On the upstream side of a quantum dot optical amplifier, a polarization beam splitter with one input and two outputs is provided. Two optical fibers connected to output sections of the polarization beam splitter are connected to input sections of the quantum dot optical amplifier in a state that both of the optical fibers have an electric field whose direction being adjusted to maximize its gain, and one optical fiber is twisted by 90.degree. to the other optical fiber. On the downstream side of the quantum dot optical amplifier, a polarization beam splitter with two inputs and one output is provided. Between two optical fibers connected to the polarization beam splitter, one is twisted by 90.degree. to the other. This twisting direction is reverse to the twisting direction of the two optical fibers connected to the input sections of the quantum dot optical amplifier.

Abstract: On the upstream side of a quantum dot optical amplifier, a polarization beam splitter with one input and two outputs is provided. Two optical fibers connected to output sections of the polarization beam splitter are connected to input sections of the quantum dot optical amplifier in a state that both of the optical fibers have an electric field whose direction being adjusted to maximize its gain, and one optical fiber is twisted by 90° to the other optical fiber. On the downstream side of the quantum dot optical amplifier, a polarization beam splitter with two inputs and one output is provided. Between two optical fibers connected to the polarization beam splitter, one is twisted by 90° to the other. This twisting direction is reverse to the twisting direction of the two optical fibers connected to the input sections of the quantum dot optical amplifier.

Abstract: Quantum dots are formed on a plurality of surfaces whose normal direction are different from each other. The quantum dots are formed on the surfaces normal to each other, whereby the polarization dependency can be eliminated as described above. Thus, the optical semiconductor device can have very low polarization dependency.

Abstract: A semiconductor device, comprising a semiconductor stacking body configured so as to sandwich an active layer by a p-type semiconductor layer and an n-type semiconductor layer and having plural regions along the active layer, plural electrodes provided on the p-type semiconductor layer or the n-type semiconductor layer and provided one for each of the plural regions, and a switch operatively connected to at least one of the plural electrodes for switching bias voltage application directions, is configured such that each of the plural regions is forward biased by a voltage applied via the electrode and becomes an amplification region when the switch is turned to one side, and is backward biased by a voltage applied via the electrode and becomes an attenuation region when the switch is turned to the other side.

Abstract: An optical transmission system includes an optical nonlinear element having nonlinear input/output characteristics, a power detector detecting a power of a specific frequency component related to an optical signal reproduced by the optical nonlinear element, and a variable amplifier amplifying or attenuating the optical signal inputted to the optical nonlinear element. Evaluation of an output waveform is performed based on the power of the specific frequency component detected by the power detector, and a gain of the variable amplifier is properly controlled, so that an input power of the optical signal inputted to the optical nonlinear element can be easily set such that a good output waveform can be obtained without directly measuring the inputted or outputted optical signal.

Abstract: An active layer contains quantum structures. The active layer amplifies light propagating therein while current is injected therein. Electrodes are provided for sections of the active layer sectionalized along a light propagation direction. The electrodes inject different currents into the sections. Current is supplied to the electrodes in such a manner that a first current density is set to one section of the active layer and a second current density is set to another section. The first current density is lower than that at a cross point and the second current density is higher than that at the cross point. The cross point is a cross point between gain coefficient curves at least two different transition wavelengths of the quantum structures. The curves are drawn in a graph showing a relation between a density of current injected into the active layer and a gain coefficient of the active layer.

Abstract: An active layer contains quantum structures. The active layer amplifies light propagating therein while current is injected therein. Electrodes are provided for sections of the active layer sectionalized along a light propagation direction. The electrodes inject different currents into the sections. Current is supplied to the electrodes in such a manner that a first current density is set to one section of the active layer and a second current density is set to another section. The first current density is lower than that at a cross point and the second current density is higher than that at the cross point. The cross point is a cross point between gain coefficient curves at least two different transition wavelengths of the quantum structures. The curves are drawn in a graph showing a relation between a density of current injected into the active layer and a gain coefficient of the active layer.

Abstract: An optical time-division multiplex signal processing apparatus includes an optical dispersion part providing optical dispersion to an optical time-division multiplex signal and an optical clock signal, an optical detector coupled optically to the optical dispersion part for detecting a beat signal formed between the optical time-division multiplex signal and the clock signal in a superposed state, and a filter connected to an output terminal of the optical detector for filtering out an electric signal of a desired frequency band from an output electric signal of said optical detector.

Abstract: In a semiconductor device comprising a semiconductor optical amplifier, in order to allow a photodetector to be integrated without causing power loss at a low cost, the semiconductor device comprises a semiconductor substrate, a semiconductor optical waveguide, at least partly capable of functioning as a semiconductor optical amplifier, to guide signal light, and a photodetector provided in a region other than a region where the semiconductor optical waveguide is provided, wherein the semiconductor optical waveguide and the photodetector are integrated on the semiconductor substrate.

Abstract: A semiconductor device, comprising a semiconductor stacking body configured so as to sandwich an active layer by a p-type semiconductor layer and an n-type semiconductor layer and having plural regions along the active layer, plural electrodes provided on the p-type semiconductor layer or the n-type semiconductor layer and provided one for each of the plural regions, and a switch operatively connected to at least one of the plural electrodes for switching bias voltage application directions, is configured such that each of the plural regions is forward biased by a voltage applied via the electrode and becomes an amplification region when the switch is turned to one side, and is backward biased by a voltage applied via the electrode and becomes an attenuation region when the switch is turned to the other side.

Abstract: A wavelength conversion device including a nonlinear medium having quantum dots uses a tunable laser as an excitation light source of optical four wave mixing, and performs wavelength conversion for a wide bandwidth signal light with optical four wave mixing by employing a control apparatus for controlling an optical system including an optical path of a signal light and an optical system including an optical path of an excitation light in correspondence with a wavelength of a signal light that is to be wavelength converted.

Abstract: A semiconductor optical device having a substrate having a surface of a first semiconductor having a first lattice constant; and a semiconductor lamination layer formed on the substrate, the semiconductor lamination layer having an active layer which contains quantum dots of a first kind made of a second semiconductor having a second lattice constant in bulk state smaller than the first lattice constant. The active layer may contain quantum dots of a second kind made of a third semiconductor having a third lattice constant in bulk state larger than the first lattice constant. The quantum dots of the first and second kinds are preferably disposed alternately along the thickness direction between the barrier layers having the first lattice constant.

Abstract: A first optical waveguide for guiding light is formed on a substrate. A surface acoustic wave transducer for generating a surface acoustic wave which propagates along a direction in which the first optical wave guide guides the light at least partial region of the first optical waveguide, is formed on the substrate. A wavelength variable laser oscillator can be formed which is easy to control and has a fast response speed.