Abstract: A system 200 for altering laser pulse duration includes a chirped fiber Bragg grating (cFBG) 122, a Faraday rotator 230, a retroreflector 240, and a fiber-optic polarization combiner 210 coupled to the chirped fiber Bragg grating 122 via the Faraday rotator 230. The combiner 210 directs a laser pulse via the Faraday rotator 230 to a first reflection in the cFBG 122, then directs the laser pulse to the retroreflector 240, then directs the laser pulse via the Faraday rotator 230 to a second reflection in the cFBG 122, and then emits the laser pulse. A three-port fiber-optic circulator 250 may serve as an input/output interface. Another system for altering laser pulse duration includes a cFBG 122, a fiber-optic polarization combiner 210 coupled to the cFBG 122, and a four-port fiber-optic circulator 550 coupled to the combiner 210 to direct a laser pulse from through the combiner 210 to the cFBG 210 via two different paths. These systems passively achieve two passes through the same cFBG 210.

Abstract: A terminated hollow-core optical fiber includes an outer capillary having an end-face, a hollow-core optical fiber having a fiber-end located inside the outer capillary a non-zero distance away from the end-face of the outer capillary, a fiber jacket disposed on a surface of the hollow-core optical fiber, and an inner capillary disposed between the fiber jacket and an inner surface of the outer capillary. The inner capillary holds the hollow-core optical fiber via the fiber jacket such that the fiber-end protrudes from the inner capillary and is suspended inside the outer capillary. The terminated hollow-core optical fiber further includes an endcap adjacent the end-face of the outer capillary. This configuration positions the sensitive and potentially fragile fiber-end close to the endcap in a protected environment, while avoiding direct contact between the fiber-end and other mechanical structures, and can be realized without fusing anything to the light-transmitting surfaces of the endcap.

Abstract: An erbium fiber laser produces a beam of ultrashort laser pulses having a center wavelength greater than 780 nanometers, an average power greater than 0.5 watt, and a pulse duration less than 200 femtoseconds. The fiber laser includes an erbium fiber amplifier that is energized by a pump beam having a pump wavelength longer than 1520 nanometers. The pump wavelength is selected to provide uniform gain over the broad spectral bandwidth of a seed beam and minimal gain at shorter wavelengths in the fiber amplifier, thereby overcoming gain narrowing and gain shifting. The pump beam has sufficient power to achieve pump saturation in the fiber amplifier.

Abstract: An erbium fiber laser produces a beam of ultrashort laser pulses having a center wavelength greater than 780 nanometers, an average power greater than 0.5 watt, and a spectral bandwidth compressible to a pulse duration of less than 200 femtoseconds. The laser includes a fiber preamplifier that is energized by a counter-propagating pump beam, has relatively low population inversion in a relatively long optical gain fiber, and provides a spectrally-shaped beam for further amplification. Wavelength dependent gain and absorption within the optical gain fiber enhances longer wavelengths relative to shorter wavelengths in the spectrally-shaped beam. The spectral shaping is sufficient to overcome gain narrowing and gain shifting in a subsequent high-gain fiber amplifier.

Abstract: An optically nonlinear crystal is arranged for frequency-doubling an input pulse. The crystal has parallel facets each coated with a reflective coating. The crystal is arranged with respect to the input pulse such that the input pulse makes a plurality of forward and reverse passes between the coatings. A frequency-doubled pulse is generated on the forward passes. The input pulse and the frequency-doubled pulse propagate with different group velocities in the crystal such that temporal separation the pulses occurs. The crystal and reflective coatings are configured such that the temporal separation does not exceed a predetermined value.

Abstract: In an optical parametric frequency conversion arrangement first and second optically nonlinear crystals (18, 20) mounted on respectively first and second drive-shafts (26, 30). The drive shafts (26, 30) are counter-rotatably driven by a single stepper-motor (50) via a gear-train. The first drive-shaft (26) includes a lead screw. When the first drive-shaft (26) is rotated, the first crystal (18) is rotated and simultaneously translated, while the second crystal (20) is simultaneously counter-rotated but is not translated.

Abstract: Radiation from a VBG-locked diode-laser at a locked wavelength of 878.6 nm is focused into a 30-mm long Nd:YVO4 optical amplifier crystal for optically pumping the crystal (24). The crystal amplifies a beam of seed-pulses from a fiber MOPA (12). The power of pump radiation is about 75 Watts. The radiation is focused into a beam-waist having a minimum diameter of about 600 micrometers. This provides an amplifier having a high gain-factor well over 100. The high-gain factor provides a gain-shaping effect on the seed-pulse beam which overcomes thermal aberrations inherent in such high-power pumping, thereby producing an amplified seed-pulse beam with M2 less than 1.3.