Semiconductor laser device, semiconductor laser module, and optical fiber amplifier

A semiconductor laser device comprising:

• an emission facet with a first reflection coating;
• a reflection facet with a second reflection coating;
• an active layer that is formed between the first reflection coating and the second reflection coating;
• and
• a grating that is disposed adjacent to the active layer and that selects a light of which number of longitudinal modes is equal to or more than 2 and equal to or less than 60, wherein each longitudinal mode has an intensity difference equal to or less than 10 decibels from a maximum intensity.

A semiconductor laser module, comprising:

• a semiconductor laser device that has
• an emission facet with a first reflection coating;
• a reflection facet with a second reflection coating;
• an active layer that is formed between the first reflection coating and the second reflection coating;
• and
• a grating that is disposed adjacent to the active layer and that selects a light of which number of longitudinal modes is equal to or more than 2 and equal to or less than 60, wherein each longitudinal mode has an intensity difference equal to or less than 10 decibels from a maximum intensity;
• an optical fiber that guides a laser light output from the semiconductor laser device to the outside;
• and
• an optical coupling lens system that optically couples the semiconductor laser device and the optical fiber.

An optical fiber amplifier, comprising:

• a pump source with a semiconductor laser module including a semiconductor laser device, an optical fiber that guides a laser light output from the semiconductor laser device to the outside, and an optical coupling lens system that optically couples the semiconductor laser device and the optical fiber, wherein the semiconductor laser device includes
• an emission facet with a first reflection coating;
• a reflection facet with a second reflection coating;
• an active layer that is formed between the first reflection coating and the second reflection coating;
• and
• a grating that is disposed adjacent to the active layer and that selects a light of which number of longitudinal modes is equal to or more than 2 and equal to or less than 60, wherein each longitudinal mode has an intensity difference equal to or less than 10 decibels from a maximum intensity;
• an optical transmission line to transmit a signal light;
• an optical fiber for amplification that is connected to the optical transmission line and amplifies the signal light based on a Raman amplification;
• a coupler that inputs a pump light from the pump source into the optical fiber;
• and
• an optical transmission line for the pump light that connects the pump source and the coupler.

A semiconductor laser device comprising:

• an emission facet with a first reflection coating;
• a reflection facet with a second reflection coating;
• an active layer formed between the first reflection coating and the second reflection coating, and outputs a laser light having a plurality of longitudinal modes;
• and
• a modulation unit that generates a modulation signal for modulating a bias current injected into the active layer and, superimposes the modulation signal on the bias current, wherein the modulation unit gives a return loss of a stimulated Brillouin scattering equal to or less than a value obtained by adding a predetermined value to a Rayleigh scattering level based on the modulation of the laser light.

A semiconductor laser device comprising:

• an emission facet with a first reflection coating;
• a reflection facet with a second reflection coating;
• an active layer formed between the first reflection coating and the second reflection coating, and outputs a laser light having a plurality of longitudinal modes;
• and
• a grating that selects a plurality of high power longitudinal modes, wherein each longitudinal mode has an intensity difference equal to or less than 10 decibels from a maximum intensity, wherein the grating gives a return loss of a stimulated Brillouin scattering equal to or less than a value obtained by adding a predetermined value to a Rayleigh scattering level based on the selected number of the high power longitudinal modes.

A semiconductor laser module, comprising:

• a semiconductor laser device that has
• an emission facet with a first reflection coating;
• a reflection facet with a second reflection coating;
• and
• an active layer formed between the first reflection coating and the second reflection coating, and outputs a laser light having a plurality of longitudinal modes;
• an optical fiber that guides a laser light output from the semiconductor laser device to the outside;
• and
• an optical coupling lens system that optically couples the semiconductor laser device and the optical fiber in such a manner that the optical coupling efficiency between the semiconductor laser device and the optical fiber is deviated from a maximum value, wherein
• the semiconductor laser module gives a return loss of a stimulated Brillouin scattering equal to or less than a value obtained by adding a predetermined value to a Rayleigh scattering level based on an attenuation of the optical coupling efficiency.

A semiconductor laser module, comprising:

• a semiconductor laser device that has
• an emission facet with a first reflection coating;
• a reflection facet with a second reflection coating;
• and
• an active layer formed between the first reflection coating and the second reflection coating, and outputs a laser light having a plurality of longitudinal modes;
• an optical fiber that guides a laser light output from the semiconductor laser device to the outside;
• and
• an optical attenuator that attenuates the laser light, wherein
• the semiconductor laser module gives a return loss of a stimulated Brillouin scattering equal to or less than a value obtained by adding a predetermined value to a Rayleigh scattering level based on the attenuation by the optical attenuator.

A Raman amplifier that uses either of a semiconductor laser device and a semiconductor laser module, as a pump source for a wideband Raman amplification, wherein

• the semiconductor laser device has an emission facet with a first reflection coating, a reflection facet with a second reflection coating, an active layer formed between the first reflection coating and the second reflection coating, a modulation unit that generates a modulation signal for modulating a bias current injected into the active layer, and superimposes the modulation signal on the bias current, wherein the modulation unit gives a return loss of a stimulated Brillouin scattering equal to or less than a value obtained by adding a predetermined value to a Rayleigh scattering level based on the modulation of the laser light, and a grating that selects a plurality of high power longitudinal modes, wherein each longitudinal mode has an intensity difference equal to or less than 10 decibels from a maximum intensity, wherein the grating gives a return loss of a stimulated Brillouin scattering equal to or less than a value obtained by adding a predetermined value to a Rayleigh scattering level based on the selected number of the high power longitudinal modes, wherein the semiconductor laser device outputs a laser light having a plurality of longitudinal modes, and
• the semiconductor laser module includes a semiconductor laser device that has an emission facet with a first reflection coating, a reflection facet with a second reflection coating, and an active layer formed between the first reflection coating and the second reflection coating, and outputs a laser light having a plurality of longitudinal modes, an optical fiber that guides a laser light output from the semiconductor laser device to the outside;
• an optical coupling lens system that optically couples the semiconductor laser device and the optical fiber in such a manner that the optical coupling efficiency between the semiconductor laser device and the optical fiber is deviated from a maximum value, wherein the semiconductor laser module gives a return loss of a stimulated Brillouin scattering equal to or less than a value obtained by adding a predetermined value to a Rayleigh scattering level based on an attenuation of the optical coupling efficiency, an optical fiber that guides a laser light output from the semiconductor laser device to the outside, and an optical attenuator that attenuates the laser light, wherein the semiconductor laser module gives a return loss of a stimulated Brillouin scattering equal to or less than a value obtained by adding 2 decibels to a Rayleigh scattering level based on the attenuation by the optical attenuator.