Abstract: There is provided a phase control portion for controlling phase of a laser beam resonated in a resonator based on detected results by two optical detectors. The phase control portion adjusts the longitudinal mode positions by a feedback control so that a ratio of intensities detected by the two optical detectors comes to a predetermined reference value. To one of the optical detectors, part of a laser beam outputted from the resonator is irradiated as it is, whereas, to the other one of the optical detectors, part of the laser beam outputted from the resonator is irradiated after passing through an etalon. An FSR of the etalon is a double of that of another etalon in the resonator.

Abstract: The optical amplifying device comprises a DFB laser 22 formed on an n type InP substrate 10, for outputting control light; a symmetrical Mach-Zehnder interferometer 12 formed on the n type InP substrate 10 and including 3 dB optical couplers 14, 16 having 2 input ports and 2 output ports, and optical waveguides 24a, 24b which optically interconnect the output port of the 3 dB optical coupler 14 and the input port of the 3 dB optical coupler 16; and SOAs 24a, 24b respectively formed in the optical waveguides 24a, 24b.

Abstract: Objects are achieved by an optical semiconductor device comprising: a structure 61 including a substrate 50, a diffraction grating 52a, an active layer 54 and a refractive index control layer 60; and an laser element 100 including an electrode 92a for the active layer, an electrode 92b for the refractive index control layer and an electrode 92c for switching, wherein a pre-bias current is previously supplied from the electrode 92a for the active layer to the active layer 54 in a state where a switching current is not supplied from the electrode 92c for switching to the active layer 54, and then while a current Idrive for activation is supplied from the electrode 92a for the active layer to the active layer 54, the laser element 100 is turned on by supplying the switching current Isw from the electrode 92c for switching to a part of the active layer 54, as well as turning off the laser element 100 by halting the supply of the switching current Isw.

Abstract: A light oscillation part including an active layer for generating light by current injection, a tuning layer with an intermediate layer formed between the active layer and the tuning layer, for varying an oscillation wavelength by current injection and a diffraction grating formed near the active layer and the tuning layer, and a light amplification part including an active layer for amplifying light by current injection are formed on a semiconductor substrate. Light oscillation elements having wide wavelength variation ranges and the light amplification are integrated on a semiconductor substrate, whereby wide wavelength variation ranges can be obtained and the output light can be much increased.

Abstract: In order to realize continuous gain control while realizing polarization independent amplifying characteristic, an optical amplifying device is configured to include: a Mach-Zehnder interferometer including an input side coupler, an output side coupler and a pair of arms, that connects the input side coupler to the output side coupler; a first and a second optical amplifier, to amplify signal light, which are disposed on the pair of arms respectively; and a light source for control light to output control light, in which the first and the second optical amplifier are configured to have polarization independent characteristic and the light source for control light is configured to have a predetermined polarization dependent gain difference or a predetermined polarization dependent loss difference.

Abstract: In a TTG-DFB-LD including a MQW wavelength control layer 16 whose refractive index varies by the current injection, the effective forbidden bandwidth of the MQW wavelength control layer 16 is larger by a value in the range of above 40 meV including 40 meV and below 60 meV excluding 60 meV than an energy of light generated in the MQW active layer 20.

Abstract: A semiconductor optical amplifier, an acousto-optic tunable filter, a phase shifter, a lens, and an internal etalon are arranged in a resonator. Outside the resonator, two lenses, two beam splitters, two photo-detectors, and an external etalon are arranged. The internal etalon is a quartz etalon and the external etalon is a crystal etalon. Therefore, the rate of change in transmission peak wavelength of the internal etalon to a temperature change is greater than that of the external etalon.

Abstract: A wavelength tunable laser device includes: a pair of reflection mirrors; a semiconductor element disposed between the pair of reflection mirrors, the semiconductor element integrating a region for providing an optical gain, a region having a wavelength tunable filter function and a phase control region; and an optical filter disposed between the semiconductor element and one of the pair of reflection mirrors, the optical filter having periodical transmission wavelengths. A wavelength tunable laser device is provided which is easy to be controlled and can be made compact.

Abstract: There is provided a phase control portion for controlling phase of a laser beam resonated in a resonator based on detected results by two optical detectors. The phase control portion adjusts the longitudinal mode positions by a feedback control so that a ratio of intensities detected by the two optical detectors comes to a predetermined reference value. To one of the optical detectors, part of a laser beam outputted from the resonator is irradiated as it is, whereas, to the other one of the optical detectors, part of the laser beam outputted from the resonator is irradiated after passing through an etalon. An FSR of the etalon is a double of that of another etalon in the resonator.

Abstract: The optical amplifying device comprises a DFB laser 22 formed on an n type InP substrate 10, for outputting control light; a symmetrical Mach-Zehnder interferometer 12 formed on the n type InP substrate 10 and including 3 dB optical couplers 14, 16 having 2 input ports and 2 output ports, and optical waveguides 24a, 24b which optically interconnect the output port of the 3 dB optical coupler 14 and the input port of the 3 dB optical coupler 16; and SOAs 24a, 24b respectively formed in the optical waveguides 24a, 24b.

Abstract: A wavelength-selectable laser with a resonance region formed by two reflecting surfaces include a gain medium generating a laser beam, a first filter, and a second filter. The first filter has a first controllable transmission region and transmits a first predetermined wavelength region of the laser beam generated in the gain medium, the first predetermined wavelength region matching the first controllable transmission region. The second filter has a plurality of periodically arranged second transmission regions and transmits a second predetermined wavelength region of the laser beam transmitted by the first filter, the second predetermined wavelength region matching one of the second transmission regions.

Abstract: An light oscillation part including an active layer 20 for generating light by current injection, a tuning layer 24 with an intermediate layer 22 formed between the active layer 20 and the tuning layer 24, for varying an oscillation wavelength by current injection and a diffraction grating 28 formed near the active layer 20 and the tuning layer 24, and a light amplification part including an active layer 20 for amplifying light by current injection are formed on a semiconductor substrate. Light oscillation elements having wide wavelength variation ranges and the light amplification are integrated on a semiconductor substrate, whereby wide wavelength variation ranges can be obtained and the output light can be much increased.

Abstract: A wavelength-selectable laser with a resonance region formed by two reflecting surfaces include a gain medium generating a laser beam, a first filter, and a second filter. The first filter has a first controllable transmission region and transmits a first predetermined wavelength region of the laser beam generated in the gain medium, the first predetermined wavelength region matching the first controllable transmission region. The second filter has a plurality of periodically arranged second transmission regions and transmits a second predetermined wavelength region of the laser beam transmitted by the first filter, the second predetermined wavelength region matching one of the second transmission regions.

Abstract: A semiconductor optical amplifier includes a plurality of active layers of bulk crystal with at least one intervening spacer for optical amplification, wherein each of the active layers accumulates a tensile strain therein.

Abstract: A polarization independent-type semiconductor optical amplifier comprises: a strained bulk active layer having a 20 nm to 90 nm-thick and having a tensile strain of a −0.10% to −0.60% strain amount; clad layers provided, sandwiching the strained bulk active layer; and a resonance suppressing means for suppressing resonance of light due to reflection on a light incident end face and a light exit end face of the strained bulk active layer, incident signal light entering at the light incident end face being amplified and exiting at the light exit end face, and an individual transmission gain of the exit signal light being substantially constant independent of a polarization state of the incident signal light. Whereby drastically increased fiber out saturation powers can be obtained with polarization independence retained.

Abstract: A light amplifying device, which employs a SOA, has been disclosed, wherein, the gain of the SOA is adjusted by the injection of light into the semiconductor optical amplifier. The signal light and the CW control light are combined, entered into the SOA, and the control light is removed from the light output from the SOA by the filter, the amplified signal light is divided by the divider, and the power of one of the divided lights is detected. The control unit changes the power of the control light in accordance with the detected power. The gain is adjusted by changing the power of the control light. In this structure, the density of the carrier in the active layer is reduced by increasing the power of the control light in order to decrease the gain, but the saturation light output power of the SOA is increased because the carrier life is reduced.

Abstract: A light amplifying device, which employs a SOA, has been disclosed, wherein, the gain of the SOA is adjusted by the injection of light into the semiconductor optical amplifier. The signal light and the CW control light are combined, entered into the SOA, and the control light is removed from the light output from the SOA by the filter, the amplified signal light is divided by the divider, and the power of one of the divided lights is detected. The control unit changes the power of the control light in accordance with the detected power. The gain is adjusted by changing the power of the control light. In this structure, the density of the carrier in the active layer is reduced by increasing the power of the control light in order to decrease the gain, but the saturation light output power of the SOA is increased because the carrier life is reduced.

Abstract: A semiconductor optical amplifier includes a plurality of active layers of bulk crystal with at least one intervening spacer for optical amplification, wherein each of the active layers accumulates a tensile strain therein.