Abstract: Encircled far field energy is substantially increased by modifying the near field energy distribution of radiation from each fiber in an emitting array. Each beamlet output from a fiber is modified to have a generally uniform cross-sectional energy distribution, using a pair of aspheric optical elements selected for that purpose. The optical elements may be refractive or reflective. The modified beamlets combine to form a composite output beam with a generally uniform energy distribution. Preferably, the composite beam is subject to an array-wide inverse transformation to a near-Gaussian distribution, further enhancing the encircled far field energy and providing a more efficient high power laser source. Further gains in efficiency are achieved by selecting a fiber bundle pattern, lens array pattern and lens shape that together result in a high fill factor.

Abstract: A system to remove cladding light from an optical fiber that includes a core and a cladding that surrounds the core. A volume of an index-matching material contacts an exterior surface of the cladding along a contact length of the optical fiber. The index-matching material has a refractive index that substantially matches a refractive index of the cladding at a predetermined clamping temperature and has a refractive index with a negative temperature coefficient, such that the index matching material distributively removes light from the cladding along the contact length based on the temperature of the index matching material that contacts the cladding.

Abstract: A fiber laser system and a related method for its use, in which one or more fiber laser amplifiers are cryogenically cooled and optimized to operate at a desirably high efficiency. Versions of the laser system using either thulium or erbium doped fibers are disclosed. In a high power version of the system, the outputs of multiple fiber lasers are coherently combined. Cooling by a selected liquefied gas, such as nitrogen, is applied to the fiber laser amplifiers and, optionally, to pump diodes and to optical elements used to combine the outputs of the fiber laser amplifiers.

Abstract: A hybrid optical/electronic wavefront sensor includes an electro-acoustical device used to upshift an optical reference signal. An optical test signal and the frequency upshifted optical reference signal are optically heterodyned to create a signal having a frequency equivalent to the beat frequency of the two signals, for example, the RF driving frequency of the Bragg cell. The optically heterodyned signal is then converted by way of a detector to an electronic signal having the same phase as the optical test signal. The output of the detector is a sinusoidal signal having the same phase as the phase of the optical test signal. This signal is filtered by way of an AC filter and mixed with a second clock signal, for example, a clock signal that is offset in frequency from the electro-acoustical drive signal by a frequency, for example, between 100 kHz and 1 MHz. These two signals are mixed by way of a mixer.

Abstract: An array of cylindrical end-caps with separate or integral lenses is stacked with its members in close contact, forming inter-cylinder gaps between every subset of three adjacent cylindrical lenses. Conductive fibers are disposed in the inter-cylinder gaps. Heat that would otherwise accumulate in the array is removed through the conductive fibers and transmitted to an external heat sink.