Abstract: A quantum dot laser includes a GaAs substrate, a quantum dot active layer which has a barrier layer of GaAs and quantum dots, a GaAs waveguide core layer which is joined to the quantum dot active layer, and a lower cladding layer and an upper cladding layer which sandwich the quantum dot active layer and the GaAs waveguide core layer. The GaAs waveguide core layer extends from a front end of the quantum dot active layer and has a thickness which gradually decreases in a direction to depart from the front end of the quantum dot active layer, a refractive index of a first cladding layer is higher than a refractive index of a second cladding layer. With this structure, expansion of the optical mode diameter that is more than necessary is inhibited to prevent leakage of light, thereby obtaining sufficient optical output.

Abstract: A laser includes first through fourth gain media, first through fifth wavelength selective filters, and first through fourth wavelength selective mirrors. The first through fourth gain media emit laser beams of different wavelengths. Each of the first through fifth wavelength selective filters includes first through fourth input/output ports. The fifth wavelength selective filter selects light of periodic wavelengths. The first through fourth wavelength selective filters have their respective first input/output ports connected to the first through fourth gain media, respectively, have their respective fourth input/output ports connected to the first through fourth wavelength selective mirrors, respectively, and have their respective second input/output ports connected to the first through fourth input/output ports, respectively, of the fifth wavelength selective filter.

Abstract: A semiconductor laser light source includes a semiconductor substrate formed of a first conductivity type semiconductor material, a lower cladding layer formed of the first conductivity type semiconductor material on the semiconductor substrate, a waveguide layer on the lower cladding layer, and an upper cladding layer formed of a second conductivity type semiconductor material on the waveguide layer. The waveguide layer includes a core area and rib areas thinner than the core area on either side of the core area. The core area has a quantum dot active layer, and the rib areas have no quantum dot layer. The waveguide layer forms a laser part having the core area with a constant width and a spot size converter having the core area with a taper width from a side adjacent to the laser part toward an end of the spot size converter.

Abstract: A laser apparatus includes first and second gain media; first, second, and third wavelength selection filters; and first and second mirrors. The wavelengths of first and second laser light emitted from end surfaces of the first and second gain media, respectively, are different from each other. The third wavelength selection filter is a wavelength selection filter to select light having wavelengths that cyclically exist in the light, as light to be selected. The other end surfaces of the first and second gain media are connected with the first input/output ports of the first and second wavelength selection filters, respectively. The fourth input/output ports of the first and second gain media are connected with the first and second mirrors, respectively. The first and second input/output ports of the third wavelength selection filter are connected with the second input/output ports of the first and second wavelength selection filters, respectively.

Abstract: An optical module including a first optical coupler; a second optical coupler; a first optical waveguide; a second optical waveguide; a first electrode provided on the first optical waveguide; a second electrode provided on the second optical waveguide; a short electrode shorter than the first and second electrodes and provided on the second optical waveguide; and a first high-frequency connector and a second high-frequency connector; wherein, the short electrode provided on the second optical waveguide is coupled to the second high-frequency connector; and the first electrode provided on the first optical waveguide is coupled to the first high-frequency connector.

Abstract: A tunable laser source includes a mirror, a tunable filter, and a semiconductor optical amplifier integrated device including first, second, and third semiconductor optical amplifiers between a first end face facing toward the tunable filter and a second end face facing away from the first end face. The first amplifier is closer to the first end face than the second and third amplifiers. The semiconductor optical amplifier integrated device further includes a partially reflecting mirror and an optical divider that are disposed between the first amplifier and the second and third amplifiers. The partially reflecting mirror is closer to the first amplifier than the optical divider. The optical divider includes first and second branches connected to the second and third semiconductor optical amplifiers, respectively. The tunable filter and the first amplifier are disposed in an optical path between the partially reflecting mirror and the mirror that form a laser resonator.

Abstract: A multi-wavelength laser light source includes a gain waveguide having a gain medium and a first mirror; and a waveguide wavelength filter, wherein the waveguide wavelength filter comprises: a first optical waveguide coupled to an end of the gain waveguide opposite to the first mirror,a plurality of ring resonators having input ports coupled to the first optical waveguide and having resonance wavelengths different from each other,a plurality of output waveguides coupled to respective output ports of the plurality of ring resonators, and second mirrors configured to correspondingly reflect, back to the plurality of ring resonators, at least part of light that has traveled via the output waveguides from the plurality of ring resonators.

Abstract: A quantum dot laser includes a GaAs substrate, a quantum dot active layer which has a barrier layer of GaAs and quantum dots, a GaAs waveguide core layer which is joined to the quantum dot active layer, and a lower cladding layer and an upper cladding layer which sandwich the quantum dot active layer and the GaAs waveguide core layer. The GaAs waveguide core layer extends from a front end of the quantum dot active layer and has a thickness which gradually decreases in a direction to depart from the front end of the quantum dot active layer, a refractive index of a first cladding layer is higher than a refractive index of a second cladding layer. With this structure, expansion of the optical mode diameter that is more than necessary is inhibited to prevent leakage of light, thereby obtaining sufficient optical output.

Abstract: A tunable laser includes: a wavelength filter that includes a first ring resonator and a second ring resonator each of which is formed by a waveguide including a silicon waveguide core, and each of which is capable of shifting each of resonance wavelengths that exit periodically and whose intervals are different from each other; and an integrated device that is optically coupled to the wavelength filter, and in which a first semiconductor optical amplifier and a reflector are provided in sequence from a side of the wavelength filter, wherein the resonance wavelengths of the first ring resonator and the second ring resonator are overlapped with each other at one wavelength, and the resonance wavelengths are overlapped with each other also at a plurality of wavelengths other than the one wavelength.

Abstract: A laser device includes an optical semiconductor device formed of a compound semiconductor material; and a wavelength-selective reflection device including optical waveguides. Further, the optical semiconductor device includes first and second gain waveguides, a DBR waveguide formed between the first and the second gain waveguides, first and second electrodes to inject current in the first and the second gain waveguides, and an antireflection film formed on a device facet to which the second gain waveguide is connected. The optical waveguides in the wavelength-selective reflection device reflect light having a predetermined wavelength from incident light in the optical waveguides. The first gain waveguide is optically coupled with the wavelength-selective reflection device, so that a laser resonator is formed by the DBR waveguide and the wavelength-selective reflection device, and the first gain waveguide functions as a gain medium.

Abstract: The present invention relates to an optical semiconductor integrated element and manufacturing method for same solves difficulty in element manufacture, and reduces optical transmission loss. The present invention is provided with a stripe-shaped waveguide configured from a multilayer structure wherein at least a first conductivity-type lower cladding layer, a waveguide core layer, and an upper cladding layer are layered, and the upper cladding layer is formed using a second conductivity-type upper cladding layer, and an i-type upper cladding layer, which has a bent portion by being shifted in the perpendicular direction with respect to the main extending direction of the waveguide.

Abstract: A laser device includes an optical semiconductor device formed of a compound semiconductor material; and a wavelength-selective reflection device including optical waveguides. Further, the optical semiconductor device includes first and second gain waveguides, a DBR waveguide formed between the first and the second gain waveguides, first and second electrodes to inject current in the first and the second gain waveguides, and an antireflection film formed on a device facet to which the second gain waveguide is connected. The optical waveguides in the wavelength-selective reflection device reflect light having a predetermined wavelength from incident light in the optical waveguides. The first gain waveguide is optically coupled with the wavelength-selective reflection device, so that a laser resonator is formed by the DBR waveguide and the wavelength-selective reflection device, and the first gain waveguide functions as a gain medium.

Abstract: A light receiving element includes a core configured to propagate a signal light, a first semiconductor layer having a first conductivity type, the first semiconductor layer being configured to receive the signal light from the core along a first direction in which the core extends, an absorbing layer configured to absorb the signal light received by the first semiconductor layer, and a second semiconductor layer having a second conductivity type opposite to the first conductivity type.

Abstract: An optical semiconductor device includes: a waveguide unit which is formed on a semiconductor substrate including a (100) plane and includes a core layer which propagates light; a spot size converting unit which is formed on the semiconductor substrate, is optically connected to the waveguide unit, and converts diameter of light propagated; and a pair of terraces which are formed on the semiconductor substrate and are opposed to each other while sandwiching the spot size converting unit. Interval between opposed units which are opposed to each other while sandwiching the spot size converting unit in the pair of terraces changes, and each of the opposed units includes a part whose orientation tilts to a [0-11] direction with respect to a [011] direction, and position of an upper end of the spot size converting unit is higher than that of an upper end of the waveguide unit.

Abstract: An optical module including a first optical coupler; a second optical coupler; a first optical waveguide; a second optical waveguide; a first electrode provided on the first optical waveguide; a second electrode provided on the second optical waveguide; a short electrode shorter than the first and second electrodes and provided on the second optical waveguide; and a first high-frequency connector and a second high-frequency connector; wherein, the short electrode provided on the second optical waveguide is coupled to the second high-frequency connector; and the first electrode provided on the first optical waveguide is coupled to the first high-frequency connector.

Abstract: A light receiving element includes a core configured to propagate a signal light, a first semiconductor layer having a first conductivity type, the first semiconductor layer being configured to receive the signal light from the core along a first direction in which the core extends, an absorbing layer configured to absorb the signal light received by the first semiconductor layer, and a second semiconductor layer having a second conductivity type opposite to the first conductivity type.

Abstract: A light receiving element includes a core configured to propagate a signal light, a first semiconductor layer having a first conductivity type, the first semiconductor layer being configured to receive the signal light from the core along a first direction in which the core extends, an absorbing layer configured to absorb the signal light received by the first semiconductor layer, and a second semiconductor layer having a second conductivity type opposite to the first conductivity type.

Abstract: A light receiving element includes a core configured to propagate a signal light, a first semiconductor layer having a first conductivity type, the first semiconductor layer being configured to receive the signal light from the core along a first direction in which the core extends, an absorbing layer configured to absorb the signal light received by the first semiconductor layer, and a second semiconductor layer having a second conductivity type opposite to the first conductivity type.

Abstract: A tapered waveguide is provided for connection between an input waveguide and a photodiode. The width of the tapered waveguide increases as it extends from the input end that is connected to the input waveguide towards the output end that is connected to the photodiode. The tapered waveguide has an optimum half spread angle to cause higher-order mode excitation when receiving optical signal from the input waveguide. The photodiode either has a constant width or increases in width as it extends away from the output end of the tapered waveguide, its half spread angle being equal to or less than the half spread angle of the tapered waveguide.

Abstract: A light receiving element includes a core configured to propagate a signal light, a first semiconductor layer having a first conductivity type, the first semiconductor layer being configured to receive the signal light from the core along a first direction in which the core extends, an absorbing layer configured to absorb the signal light received by the first semiconductor layer, and a second semiconductor layer having a second conductivity type opposite to the first conductivity type.