Fiber-laser pumped by stabilized diode-laser bar stack
View Patent ↗A fiber is laser is pumped by radiation from a plurality of diode-laser bars which are wavelength-locked by a single feedback mirror in combination with a single band-pass filter. The locked wavelength of the plurality of diode-laser bars is tunable by tilt-tuning the band-pass filter.
1. Fiber laser apparatus comprising:
a gain-fiber;
a band-pass filter including at least one filter element;
a partially reflective and partially transmissive feedback mirror;
a focusing lens;
a plurality of diode-laser bars each thereof including a plurality of diode-laser emitters each emitter for emitting a beam of radiation having a lasing wavelength, the diode-laser bars and emitters therein characterized as having a slow-axis in the length of the diode-laser bars, a fast-axis in the height direction of the diode-laser bars and a propagation axis perpendicular to the fast-axis and the slow-axis;
each diode-laser bar having a first collimating lens associated therewith for collimating the beams of radiation from the emitters in the fast-axis, and plurality of second collimating lenses associated therewith for collimating the fast-axis collimated beams in the slow-axis thereby producing a set of fast- and slow-axis collimated beams propagating from each of the diode-laser bars;
wherein the fast- and slow-axis collimated beam-sets are transmitted through the band-pass filter in a forward direction on beam-paths parallel to each other in the fast-axis to the feedback mirror, the feedback mirror being arranged to reflect a first portion of the radiation in each of the beams-sets back through the band-pass filter in a reverse direction along the beam paths to the diode-laser bars from which the beam-sets were emitted for locking the lasing wavelength at a value determined by the band-pass filter; and
wherein a second portion of the radiation in the beam-sets is transmitted through the feedback mirror to the focusing lens, and focused by the focusing lens into one end of the gain-fiber for optically pumping the gain-fiber.
2. The apparatus of claim 1 wherein band-pass filter includes only one filter element arranged at a non-normal angle of incidence to the beam paths.
3. The apparatus of claim 2 , wherein the angle of incidence of the filter element is between about 5 and 20 degrees.
4. The apparatus of claim 2 , wherein the angle of incidence of the filter element is variable for varying the lasing wavelength of the diode-laser bars.
5. The apparatus of claim 1 , wherein the band-pass filter includes two filter elements, each thereof arranged at a non-normal angle of incidence to the beam paths.
6. The apparatus of claim 5 , wherein the angle of incidence each of the filter elements is variable for varying the lasing wavelength of the diode-laser bars.
7. The apparatus of claim 5 , wherein the filter elements are reflective elements, and wherein the fast- and slow-axis collimated beam-sets are transmitted through the band-pass filter by reflection from each of the filter elements.
8. The apparatus of claim 1 , wherein the feedback-mirror has a reflectivity between about 5% and 10% at the lasing wavelength.
9. The apparatus of claim 1 , wherein the gain-fiber has a laser-resonator formed therein.
10. The apparatus of claim 1 wherein the gain-fiber is fiber-amplifier stage of the apparatus.
11. Fiber laser apparatus comprising:
a gain-fiber;
a band-pass filter;
a partially reflective and partially transmissive feedback mirror;
a focusing lens;
a plurality of diode-laser bars each thereof including a plurality of diode-laser emitters each emitter for emitting a beam of radiation having a lasing wavelength, the diode-laser bars and emitters therein characterized as having a slow-axis in the length of the diode-laser bars, a fast-axis in the height direction of the diode-laser bars and a propagation axis perpendicular to the fast-axis and the slow-axis;
each diode-laser bar having a first collimating lens associated therewith for collimating the beams of radiation from the emitters in the fast-axis, and plurality of second collimating lenses associated therewith for collimating the fast-axis collimated beams in the slow-axis thereby producing a set of fast- and slow-axis collimated beams propagating from each of the diode-laser bars;
wherein the fast- and slow-axis collimated beam-sets are transmitted through the band-pass filter in a forward direction on beam-paths parallel to each other in the fast-axis to the feedback mirror, the feedback mirror being arranged to reflect a first portion of the radiation in each of the beams-sets back through the band-pass filter in a reverse direction along the beam paths to the diode-laser bars from which the beam-sets were emitted for locking the lasing wavelength at a value determined by the band-pass filter;
wherein the band-pass filter is at a non-normal incidence angle to the beam paths, the incidence angle being selectively variable for selectively varying the locked lasing wavelength; and
wherein a second portion of the radiation in the beam-sets is transmitted through the feedback mirror to the focusing lens, and focused by the focusing lens into one end of the gain-fiber for optically pumping the gain-fiber.
12. The apparatus of claim 11 , wherein the angle of incidence of the filter element is between about 5 and 20 degrees.