Raman Distributed Feedback Fiber Laser and High Power Laser System Using the Same

A fiber Raman laser cavity, comprising:

• a pump laser;
• an optical input enabled to receive radiation from the pump laser;
• a Raman gain fiber comprising at least one Bragg grating enabled to provide Raman radiation;
• the fiber Bragg grating having a phase shift, wherein the Bragg grating is chirped to cause a Bragg wavelength excursion along at least a part of a length of the Bragg grating, wherein an intensity of an associated optical field is large in relation to a different part of the length of the Bragg grating, wherein a location of a largest negative Bragg wavelength excursion is coincident with a location of the phase-shift of the at least one Bragg grating;
• and
• an output to provide Raman radiation.

A fiber Raman laser cavity, comprising:

• a pump laser;
• an optical input enabled to receive radiation from the pump laser;
• a Raman gain fiber comprising at least one Bragg grating enabled to provide Raman radiation;
• a temperature control element to control a temperature excursion along at least a part of a length of the Bragg grating wherein an intensity of an associated optical field is large in relation to a different part of the length of the Bragg grating, wherein a location of a largest temperature excursion is coincident with a location of the phase-shift;
• and
• an output to provide Raman radiation.

A Raman laser, comprising:

• an optical input enabled to receive radiation from a pump laser;
• and
• a first Raman gain fiber less than 20 cm in length connected to the optical input and comprising at least one Bragg grating enabled to provide Raman radiation on a first optical output;
• a second Raman gain fiber less than 20 cm in length connected in series with the first Raman gain fiber to the first optical output, the second Raman gain fiber comprising at least one Bragg grating enabled to provide Raman radiation on a second optical output;
• wherein the second Raman gain fiber is amplified by unabsorbed output from the pump laser.