Abstract: Apparatus for optically pumping a clad amplifier fiber includes one or more transmission fibers arranged and configured to insert pump-light from a pump light source such as a diode-laser into the cladding of the amplifier fiber. The pump light propagates through the cladding and a portion of the pump light is absorbed in the doped core of the amplifier fiber. At least one of the transmission fibers is arranged to receive an unabsorbed portion of the propagated pump light from the amplifier cladding and re-insert the unabsorbed portion of the pump-light into the cladding for re-propagation through the cladding. This provides that pump light that would otherwise be wasted is circulated through the amplifier fiber for further absorption by the amplifier core.

Abstract: A multimode to low-mode optical fiber is constructed by forming a plurality of multimode optical fibers into a fiber bundle. The bundle is then selectively heated and drawn to form a bi-tapered fiber bundle having a central straight portion in which the multimode fibers are fused into a single length of fiber. During the drawing step, measures are taken to provide an aperture extending through the bi-tapered bundle, including the single straight portion of the bundle. An optical fiber having a low-mode or single-mode core is inserted through the aperture into the straight section of the bi-tapered bundle. The bi-tapered bundle and the low-mode core fiber are heated to a temperature at which cladding of the low-mode core fiber fuses to the straight portion of the bi-tapered bundle. The bi-tapered bundle is then cleaved in the straight portion to provide the multimode to low-mode optical fiber combiner. In one example, the multimode fiber bundle is formed around a metal wire before the drawing operation.

Abstract: A fiber laser including doped-core fiber having inner and outer cladding is optically pumped by plurality of diode-lasers. Light emitted by the diode-lasers is coupled into a single multimode optical fiber. Light from the multimode optical fiber is directed to a wavelength selective reflecting device that is partially reflective in a narrow reflection band about a peak reflection wavelength. A portion of the light having the peak reflection wavelength is reflected from the wavelength selective reflecting device back along the multimode optical fiber and back into the plurality of diode-lasers. This locks the emitting wavelength of the light emitted from each of the diode-lasers to the peak reflection wavelength. Light at the emitting wavelength that is not reflected from the wavelength selective reflective device is coupled into the inner cladding of the doped-core fiber for optically pumping the fiber laser.

Abstract: A fiber amplifier module for amplifying a signal pulse includes an optically pumped double-pass fiber amplifier in which a fiber Bragg grating reflects an amplified pulse in between the first and second amplification passes, and transmits most forward-propagating amplified spontaneous emission (ASE) generated by the optical pumping. The reflected amplified pulse from the double-pass amplifier, and reverse-propagating ASE generated by the optical pumping are reflected from another fiber Bragg grating that again reflects the amplified pulse and transmits most of the ASE. The twice-reflected amplified pulse can be delivered from the amplifier as an output pulse or passed to another amplifier module for further amplification. The amplifier fiber is operated in a saturated or near saturated mode. This reduces amplification of any portion of the forward-propagating ASE that is reflected into reverse propagation by the fiber Bragg grating of the double-pass amplifier.

Abstract: A fiber amplifier module for amplifying a signal pulse includes an optically pumped double-pass fiber amplifier in which a fiber Bragg grating reflects an amplified pulse in between the first and second amplification passes, and transmits most forward-propagating amplified spontaneous emission (ASE) generated by the optical pumping. The reflected amplified pulse from the double-pass amplifier, and reverse-propagating ASE generated by the optical pumping are reflected from another fiber Bragg grating that again reflects the amplified pulse and transmits most of the ASE. The twice-reflected amplified pulse can be delivered from the amplifier as an output pulse or passed to another amplifier module for further amplification. The amplifier fiber is operated in a saturated or near saturated mode. This reduces amplification of any portion of the forward-propagating ASE that is reflected into reverse propagation by the fiber Bragg grating of the double-pass amplifier.

Abstract: A fiber amplifier module for amplifying a signal pulse includes an optically pumped double-pass fiber amplifier in which a fiber Bragg grating reflects an amplified pulse in between the first and second amplification passes, and transmits most forward-propagating amplified spontaneous emission (ASE) generated by the optical pumping. The reflected amplified pulse from the double-pass amplifier, and reverse-propagating ASE generated by the optical pumping are reflected from another fiber Bragg grating that again reflects the amplified pulse and transmits most of the ASE. The twice-reflected amplified pulse can be delivered from the amplifier as an output pulse or passed to another amplifier module for further amplification. The amplifier fiber is operated in a saturated or near saturated mode. This reduces amplification of any portion of the forward-propagating ASE that is reflected into reverse propagation by the fiber Bragg grating of the double-pass amplifier.

Abstract: Apparatus for optically pumping a clad amplifier fiber includes one or more transmission fibers arranged and configured to insert pump-light from a pump light source such as a diode-laser into the cladding of the amplifier fiber. The pump light propagates through the cladding and a portion of the pump light is absorbed in the doped core of the amplifier fiber. At least one of the transmission fibers is arranged to receive an unabsorbed portion of the propagated pump light from the amplifier cladding and re-insert the unabsorbed portion of the pump-light into the cladding for re-propagation through the cladding. This provides that pump light that would otherwise be wasted is circulated through the amplifier fiber for further absorption by the amplifier core.

Abstract: A fiber-laser comprises a laser cavity including a gain-fiber. A polarization maintaining fiber coupler (PM-coupler) located in the laser cavity and configured such that the fiber-laser delivers plane-polarized output radiation. The laser cavity may be configured as a linear cavity or as a ring cavity and operated in either cavity configuration in CW or pulsed modes. The PM-coupler, while providing the function of a intra-cavity polarizing element, can additionally function as a wavelength division multiplexing (WDM) coupler. Preferred embodiments of the laser include an intracavity polarization maintaining WDM element functioning jointly as an intra-cavity polarizing element and an element for coupling pump light into the cavity.

Abstract: Apparatus for optically pumping a clad amplifier fiber includes one or more transmission fibers arranged and configured to insert pump-light from a pump light source such as a diode-laser into the cladding of the amplifier fiber. The pump light propagates through the cladding and a portion of the pump light is absorbed in the doped core of the amplifier fiber. At least one of the transmission fibers is arranged to receive an unabsorbed portion of the propagated pump light from the amplifier cladding and re-insert the unabsorbed portion of the pump-light into the cladding for re-propagation through the cladding. This provides that pump light that would otherwise be wasted is circulated through the amplifier fiber for further absorption by the amplifier core.

Abstract: A fiber amplifier module for amplifying a signal pulse includes an optically pumped double-pass fiber amplifier in which a fiber Bragg grating reflects an amplified pulse in between the first and second amplification passes, and transmits most forward-propagating amplified spontaneous emission (ASE) generated by the optical pumping. The reflected amplified pulse from the double-pass amplifier, and reverse-propagating ASE generated by the optical pumping are reflected from another fiber Bragg grating that again reflects the amplified pulse and transmits most of the ASE. The twice-reflected amplified pulse can be delivered from the amplifier as an output pulse or passed to another amplifier module for further amplification. The amplifier fiber is operated in a saturated or near saturated mode. This reduces amplification of any portion of the forward-propagating ASE that is reflected into reverse propagation by the fiber Bragg grating of the double-pass amplifier.

Abstract: A fiber laser including doped-core fiber having inner and outer cladding is optically pumped by plurality of diode-lasers. Light emitted by the diode-lasers is coupled into a single multimode optical fiber. Light from the multimode optical fiber is directed to a wavelength selective reflecting device that is partially reflective in a narrow reflection band about a peak reflection wavelength. A portion of the light having the peak reflection wavelength is reflected from the wavelength selective reflecting device back along the multimode optical fiber and back into the plurality of diode-lasers. This locks the emitting wavelength of the light emitted from each of the diode-lasers to the peak reflection wavelength. Light at the emitting wavelength that is not reflected from the wavelength selective reflective device is coupled into the inner cladding of the doped-core fiber for optically pumping the fiber laser.

Abstract: Apparatus for optically pumping a clad amplifier fiber includes one or more transmission fibers arranged and configured to insert pump-light from a pump light source such as a diode-laser into the cladding of the amplifier fiber. The pump light propagates through the cladding and a portion of the pump light is absorbed in the doped core of the amplifier fiber. At least one of the transmission fibers is arranged to receive an unabsorbed portion of the propagated pump light from the amplifier cladding and re-insert the unabsorbed portion of the pump-light into the cladding for re-propagation through the cladding. This provides that pump light that would otherwise be wasted is circulated through the amplifier fiber for further absorption by the amplifier core.