Optical semiconductor apparatus, a method of driving the same and an optical transmission system using the same

A method of driving an optical semiconductor apparatus, said method comprising the steps of:

• (a) providing an optical semiconductor apparatus, the semiconductor apparatus comprising:
• a substrate;
• a plurality of semiconductor layers formed on the substrate,
• at least an upper waveguide and a lower waveguide fabricated in the semiconductor layers, the upper and lower waveguides being separated from each other in a direction of the semiconductor layers and being coupled to each other to a predetermined coupling degree;
• a semiconductor laser positioned on said substrate so that light emitted therefrom enters one of the upper and lower waveguides;
• and
• a photodetector positioned on said substrate so as to receive light from one of the upper and lower waveguides;
• (b) causing light incident on the optical semiconductor apparatus to enter one of the upper and lower waveguides;
• (c) causing the semiconductor laser to generate a local oscillation light beam;
• (d) coupling the incident light to the local oscillation light beam to a predetermined coupling degree;
• and
• (e) performing a heterodyne detection with the photodetector to detect information carried by the incident light.

A method of driving an optical semiconductor apparatus, said method comprising the steps of:

• (a) providing an optical semiconductor apparatus, the semiconductor apparatus comprising:
• a substrate;
• a plurality of semiconductor layers formed on the substrate,
• at least an upper waveguide and a lower waveguide fabricated in the semiconductor layers, the upper and lower waveguides being separated from each other in a direction of the semiconductor layers and being coupled to each other to a predetermined coupling degree;
• a semiconductor laser positioned on the substrate so that light emitted therefrom enters one of the upper and lower waveguides;
• and
• a photodetector positioned on the substrate so as to receive light from one of the upper and lower waveguides;
• (b) causing light incident on the optical semiconductor apparatus to enter one of the upper and lower waveguides;
• (c) causing the semiconductor laser to generate a local oscillation light beam;
• (d) coupling the incident light to the local oscillation light beam to a predetermined coupling degree;
• and
• (e) performing a heterodyne detection with the photodetector while stabilizing one of the oscillation wavelength and the phase of the semiconductor laser by using a signal detected by the photodetector to detect information carried by the incident light.

A method of driving an optical semiconductor apparatus, said method comprising the steps of:

• (a) providing an optical semiconductor apparatus, the semiconductor apparatus comprising:
• a substrate;
• a plurality of semiconductor layers formed on the substrate;
• at least an upper waveguide and a lower waveguide fabricated in the semiconductor layers, the upper and lower waveguides being separated from each other in a direction of the semiconductor layers and being coupled to each other to a predetermined coupling degree;
• a semiconductor laser positioned on the substrate so that light emitted therefrom enters one of the upper and lower waveguides;
• a photodetector positioned on said substrate so as to receive light from one of the upper and lower waveguides;
• and
• (b) applying a voltage to a portion of the upper and lower waveguides to change a refractive index thereof so that the degree of coupling between the upper and lower waveguides is controlled.

A method of driving an optical semiconductor apparatus, said method comprising the steps of:

• (a) providing an optical semiconductor apparatus, the semiconductor apparatus comprising:
• a substrate;
• a plurality of semiconductor layers formed on the substrate;
• at least an upper waveguide and a lower waveguide fabricated in the semiconductor layers, the upper and lower waveguides being separated from each other in a direction of the semiconductor layers and being coupled to each other to a predetermined coupling degree;
• a semiconductor laser positioned on said substrate so that light emitted therefrom enters one of the upper and lower waveguides;
• a photodetector positioned on said substrate so as to receive light from one of the upper and lower waveguides;
• a grating formed in or in the vicinity of one of the upper and lower waveguides so that the coupling between the upper and lower waveguides has the property of wavelength-selectivity;
• and
• control means for controlling the wavelength-selectivity so that a selection wavelength of the coupling is changeable;
• (b) causing light incident on the optical semiconductor apparatus to enter one of the upper and lower waveguides;
• (c) causing the semiconductor laser to generate a local oscillation light beam;
• (d) adjusting the selection-wavelength to be the wavelength of the incident light with the control means only when the apparatus performs a signal receiving operation;
• (e) performing a heterodyne detection with the photodetector to detect information carried by the incident light;
• and
• (f) changing the selection-wavelength to deviate from the wavelength of the incident light with the control means when the apparatus does not perform the signal receiving operation.

A method of driving an optical semiconductor apparatus, said method comprising the steps of:

• (a) providing an optical semiconductor apparatus, said semiconductor apparatus comprising:
• a substrate;
• a plurality of semiconductor layers formed on the substrate;
• at least an upper waveguide and a lower waveguide fabricated in the semiconductor layers, the upper and lower waveguides being separated from each other in a direction of the semiconductor layers and being coupled to each other to a predetermined coupling degree;
• a semiconductor laser positioned on said substrate so that light emitted therefrom enters one of the upper and lower waveguides;
• a photodetector positioned on said substrate so as to receive light from one of the upper and lower waveguides;
• and
• control means for controlling the degree of coupling;
• (b) adjusting the degree of coupling to be approximately 100% with said control means when the apparatus does not perform signal receiving;
• and
• (c) causing the semiconductor laser to transmit an oscillating laser beam when the apparatus does not perform signal receiving.

A method of driving an optical semiconductor apparatus, said method comprising the steps of:

• (a) providing an optical semiconductor apparatus, the semiconductor apparatus comprising:
• a substrate;
• a plurality of semiconductor layers formed on the substrate;
• at least an upper waveguide and a lower waveguide fabricated in the semiconductor layers, the upper and lower waveguides being separated from each other in a direction of the semiconductor layers and being coupled to each other to a predetermined coupling degree;
• a semiconductor laser positioned on said substrate so that light emitted therefrom enters one of the upper and lower waveguides;
• a photodetector positioned on said substrate so as to receive light from one of the upper and lower waveguides;
• control means for controlling the degree of coupling;
• (b) causing light incident on the optical semiconductor apparatus to enter one of the upper and lower waveguides;
• (c) adjusting the degree of coupling to assume a large value with said control means;
• (d) performing a heterodyne detection with said photodetector to detect information carried by the incident light;
• (e) modulating the output of the semiconductor laser based on the detected information to generate a signal;
• and
• (f) causing the signal generated in said modulating step to be transmitted to the exterior of the optical semiconductor apparatus.

An optical transmission system comprising:

• (a) a transmission line;
• (b) a plurality of nodes interconnected by said transmission line, at least one of said nodes containing an optical semiconductor apparatus, said semiconductor apparatus comprising:
• a substrate;
• a plurality of semiconductor layers formed on said substrate;
• at least an upper waveguide and a lower waveguide fabricated in said semiconductor layers, said upper and lower waveguides being separated from each other in a direction of said semiconductor layers and being coupled to each other to a predetermined coupling degree;
• a semiconductor laser positioned on said substrate so that light emitted therefrom enters one of said upper and lower waveguides;
• a photodetector positioned on said substrate so as to receive light from one of said upper and lower waveguides;
• a grating formed in or in the vicinity of one of said upper and lower waveguides so that the coupling between said upper and lower waveguides has the property of wavelength-selectivity;
• and
• control means for controlling the wavelength-selectivity so that a selection wavelength of the coupling is changeable,
• wherein said control means adjusts the selection-wavelength to be the wavelength of light incident on said optical semiconductor apparatus only when said optical semiconductor apparatus performs a signal receiving operation, and wherein said control means adjusts the selection-wavelength to deviate from the wavelength of the incident light when said optical semiconductor apparatus does not perform the signal receiving operation.

An optical transmission system comprising:

• (a) a transmission line;
• (b) a plurality of nodes interconnected by said transmission line, at least one of said nodes containing an optical semiconductor apparatus, said semiconductor apparatus comprising:
• a substrate;
• a plurality of semiconductor layers formed on said substrate;
• at least an upper waveguide and a lower waveguide fabricated in said semiconductor layers, said upper and lower waveguides being separated from each other in a direction of said semiconductor layers and being coupled to each other to a predetermined coupling degree;
• a semiconductor laser positioned on said substrate so that light emitted therefrom enters one of said upper and lower waveguides;
• a photodetector positioned on said substrate so as to receive light from one of said upper and lower waveguides;
• and
• control means for controlling the degree of coupling,
• wherein the degree of coupling is adjusted to approximately 100% by said control means when said optical semiconductor apparatus does not perform a signal receiving operation and wherein said semiconductor laser oscillates and transmits a laser beam when said optical semiconductor apparatus does not perform the signal receiving operation.

An optical transmission system comprising:

• (a) a transmission line;
• (b) a plurality of nodes interconnected by said transmission line, at least one of said nodes containing an optical semiconductor apparatus, said semiconductor apparatus comprising:
• a substrate;
• a plurality of semiconductor layers formed on said substrate;
• at least an upper waveguide and a lower waveguide fabricated in said semiconductor layers, said upper and lower waveguides being separated from each other in a direction of said semiconductor layers and being coupled to each other to a predetermined coupling degree;
• a semiconductor laser positioned on said substrate so that light emitted therefrom enters one of said upper and lower waveguides;
• a photodetector positioned on said substrate so as to receive light from one of said upper and lower waveguides;
• and
• control means for controlling the degree of coupling,
• wherein the degree of coupling is adjusted to a large value by said control means, wherein a heterodyne detection is performed by said photodetector to detect information carried by light incident on said optical semiconductor device and wherein light emitted from said semiconductor laser is modulated based on the detected information to generate a signal which is to be transmitted to the exterior of said optical semiconductor apparatus.