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US 6,785,312 B2Granted
Semiconductor laser and system for and method of performing digital optical communications using such semiconductor laser
AssigneeNEC Corporation
InventorKenji Sato
Life of this patent
Estimating the term…
Abstract
A digital optical communication method transmits an optical signal over a long distance with a reduced power penalty. The method has the step of shaping the waveform of the optical signal to be transmitted through the optical fiber to increase the frequency thereof before the waveform is stabilized when the optical signal starts increasing in level at the time the optical signal is applied to the optical fiber.
Claims12
A semiconductor laser that modulates from a first level to a second level, comprising:
- a diffraction grating for effecting distribution feedback, said diffraction grating having a normalized coupling coefficient κL of at least 2.0, said diffraction grating having a phase shift region disposed therein for achieving a phase shift of at most λ/4;
- and
- an active layer including a multiple quantum well structure, having a gain saturation coefficient of greater than 0, such that said gain is saturated as a carrier concentration in the active layer increases.
A semiconductor laser, comprising:
- a diffraction grating for effecting distribution feedback, said diffraction grating having a normalized coupling coefficient κL of at least 2.0, said diffraction grating having a phase shift region disposed therein for achieving a phase shift of at most λ/4;
- and
- an active layer including a gain, which is saturated as a carrier concentration in the active layer increases,
- wherein said active layer includes a multiple quantum well structure having growth surface irregularities.
1 more element
A semiconductor laser, comprising:
- a diffraction grating for effecting distribution feedback, said diffraction grating having a normalized coupling coefficient λL of at least 2.0, said diffraction grating having a phase shift region disposed therein for achieving a phase shift of at most λ/4;
- an active layer including a gain, which is saturated as a carrier concentration in the active layer increases;
- and
- a resonator, said phase shift region being disposed nearly centrally in said resonator,
- wherein said active layer includes a multiple quantum well structure having growth surface irregularities.
2 more elements
A semiconductor laser, comprising:
- a diffraction grating for effecting distribution feedback, said diffraction grating having a normalized coupling coefficient κL of at least 2.0, said diffraction grating having a phase shift region disposed therein for achieving a phase shift of at most λ/4;
- and
- an active layer including a gain, which is saturated as a carrier concentration in the active layer increases,
- wherein said active layer includes a multiple quantum well structure comprising two stage potential quantum wells.
1 more element
A semiconductor laser, comprising:
- a diffraction grating for effecting distribution feedback, said diffraction grating having a normalized coupling coefficient κL of at least 2.0, said diffraction grating having a phase shift region disposed therein for achieving a phase shift of at most λ/4;
- an active layer including a gain, which is saturated as a carrier concentration in the active layer increases;
- and
- a resonator, said phase shift region being disposed nearly centrally in said resonator,
- wherein said active layer includes a multiple quantum well structure comprising two stage potential quantum wells.
2 more elements
A semiconductor laser, comprising:
- a diffraction grating for effecting distribution feedback, said diffraction grating having a normalized coupling coefficient λL of at least 2.0, said diffraction grating having a phase shift region disposed therein for achieving a phase shift of at most λ/4;
- and
- an active layer including a gain, which is saturated as a carrier concentration in the active layer increases,
- wherein said active layer includes a multiple quantum well structure including a non-radiative carrier recombination layer.
1 more element
A semiconductor laser, comprising:
- a diffraction grating for effecting distribution feedback, said diffraction grating having a normalized coupling coefficient κL of at least 2.0, said diffraction grating having a phase shift region disposed therein for achieving a phase shift of at most λ/4;
- an active layer including a gain, which is saturated as a carrier concentration in the active layer increases;
- and
- a resonator, said phase shift region being disposed nearly centrally in said resonator,
- wherein said active layer includes a multiple quantum well structure including a non-radiative carrier recombination layer.
2 more elements
A semiconductor laser, comprising:
- a diffraction grating for effecting distribution feedback, said diffraction grating having a normalized coupling coefficient κL of at least 2.0, said diffraction grating having a phase shift region disposed therein for achieving a phase shift of at most λ/4;
- and
- an active layer including a gain, which is saturated as a carrier concentration in the active layer increases,
- wherein said active layer includes a multiple quantum well structure which is progressively thicker toward the center of the semiconductor laser in the axial direction of the resonator.
1 more element
A semiconductor laser, comprising:
- a diffraction grating for effecting distribution feedback, said diffraction grating having a normalized coupling coefficient κL of at least 2.0, said diffraction grating having a phase shift region disposed therein for achieving a phase shift of at most λ/4;
- an active layer including a gain, which is saturated as a carrier concentration in the active layer increases;
- and
- a resonator, said phase shift region being disposed nearly centrally in said resonator,
- wherein said active layer includes a multiple quantum well structure which is progressively thicker toward the center of the semiconductor laser in the axial direction of the resonator.
2 more elements
Dependencies are inferred from the claim text.