Wavelength-variable laser

A semiconductor laser module comprising:

• an optical semiconductor device which is a semiconductor laser element outputting a predetermined wavelength of laser light comprising:
• a quantum well active layer positioned between a p-type cladding layer and an n-type cladding layer in thickness direction;
• a separate confinement heterostructure layer positioned between the quantum well active layer and the n-type cladding layer;
• and
• an electric-field-distribution-control layer positioned between the separate confinement heterostructure layer and the n-type cladding layer and configured by at least two semiconductor layers having band gap energy greater than band gap energy of a barrier layer constituting the quantum well active layer;
• a temperature-control module controlling temperature of the semiconductor laser element;
• an optical fiber guiding the laser light outputted from the semiconductor laser element to outside;
• and
• an optical-coupling lens system coupling the semiconductor laser element and the optical fiber optically, wherein the optical semiconductor device is fabricated on a GaAs substrate, and
• by using an element having an electric-field adjusting layer, an optical feedback unit, which returns a part of laser light to a semiconductor laser element, is disposed, and a cavity together with a reflection end surface of the semiconductor laser element are formed.

An optical fiber amplifier comprising:

• a semiconductor laser module comprising:
• an optical semiconductor device which is a semiconductor laser element outputting a predetermined wavelength of laser light comprising:
• a quantum well active layer positioned between a p-type cladding layer and an n-type cladding layer in thickness direction;
• a separate confinement heterostructure layer positioned between the quantum well active layer and the n-type cladding layer;
• and
• an electric-field-distribution-control layer positioned between the separate confinement heterostructure layer and the n-type cladding layer and configured by at least two semiconductor layers having band gap energy greater than band gap energy of a barrier layer constituting the quantum well active layer;
• a temperature-control module controlling temperature of the semiconductor laser element;
• an optical fiber guiding the laser light outputted from the semiconductor laser element to outside;
• and
• an optical-coupling lens system coupling the semiconductor laser element and the optical fiber optically;
• an amplification optical fiber including amplification medium;
• and
• an optical coupler multiplexing inputted signal light and the laser light outputted from the semiconductor laser module and making the multiplexed light input into the amplification optical fiber, wherein the optical semiconductor device is fabricated on a GaAs substrate, and
• by using an element having an electric-field adjusting layer, an optical feedback unit, which returns a part of laser light to a semiconductor laser element, is disposed, and a cavity together with a reflection end surface of the semiconductor laser element are formed.

An optical fiber amplifier comprising:

• a semiconductor laser module comprising:
• an optical semiconductor device which is a semiconductor laser element outputting a predetermined wavelength of laser light comprising:
• a quantum well active layer positioned between a p-type cladding layer and an n-type cladding layer in thickness direction;
• a separate confinement heterostructure layer positioned between the quantum well active layer and the n-type cladding layer;
• and
• an electric-field-distribution-control layer positioned between the separate confinement heterostructure layer and the n-type cladding layer and configured by at least two semiconductor layers having band gap energy greater than band gap energy of a barrier layer constituting the quantum well active layer;
• a temperature-control module controlling temperature of the semiconductor laser element;
• an optical fiber guiding the laser light outputted from the semiconductor laser element to outside;
• and
• an optical-coupling lens system coupling the semiconductor laser element and the optical fiber optically;
• an optical fiber transmitting signal light;
• and
• an optical coupler making the laser light outputted from the semiconductor laser module input into the optical fiber, wherein
• an optical amplification is performed by Raman amplification, wherein the optical semiconductor device is fabricated on a GaAs substrate, and
• by using an element having an electric-field adjusting layer, an optical feedback unit, which returns a part of laser light to a semiconductor laser element, is disposed, and a cavity together with a reflection end surface of the semiconductor laser element are formed.