Massachusetts Institute of Technology

Steven J Augst

Tso Yee Fan

Antonio Sanchez-Rubio

Bien Chann

Juan Montoya

Kelsey Yee

Steven R Gillmer

Jonathan Wilson

Andrew Guzman

Joseph Flaherty

Kevin Edward Sullivan

Franklin Jose

Peter O'Brien

High-power light absorbers (HPLAs) can exhibit low back-scattered light, mitigate stray light, and withstand high optical power. The absorbers can be used with or without baffling as beam dumps for high-power lasers. An HPLA may include a substrate made of high thermally conductive material with an anti-reflection (AR) coating formed on the substrate. A thin layer of highly absorbing material may be located between the AR coating and substrate. The substrate can be cooled with a fluid, such as water or air.

High power light absorbers having anti-reflection coating

A ruggedized adjustable mounting system is described for adjustably coupling and selectively locking a component supported in a fixture of the mount in a desired orientation. In some embodiments, the mounting system includes one or more kinematic couplings that support a fixture on a base and one or more adjustable couplings that are configured to adjust a separation distance between two opposing portions of the fixture and the base to selectively pivot the fixture about one or more axes of rotation.

Adjustable alignment mount

Stimulated Brillouin scattering (SBS) limits the maximum power in fiber lasers with narrow linewidths. SBS occurs when the power exceeds a threshold proportional to the beam area divided by the effective fiber length. The fiber lasers disclosed here operate with higher SBS power thresholds (and hence higher maximum powers at kilohertz-class linewidths) than other fiber lasers thanks to several techniques. These techniques include using high-absorption gain fibers, operating the laser with low pump absorption (e.g., &#x2264;80%), reducing the length of un-pumped gain fiber at the fiber output, foregoing a delivery fiber at the output, foregoing a cladding light stripper at the output, using free-space dichroic mirrors to separate signal light from unabsorbed pump light, and using cascaded gain fibers with non-overlapping Stokes shifts. The upstream gain fiber has high absorption and a larger diameter for high gain, and subsequent gain fiber has a smaller diameter to improve beam quality.

Single-frequency fiber amplifier with distal cladding stripper

A fiber amplifier includes an isolator, a gain fiber to amplify an input laser signal, and an optical filter disposed between the isolator and the gain fiber. The optical filter transmits the laser signal and reflects amplified spontaneous emission (ASE) propagating from the gain fiber toward the isolator. The reflected ASE reenters the gain fiber and is absorbed by the gain fiber for amplifying the input laser signal. The optical filter in the amplifier can protect the usually expensive isolator and reduce potential damage to the gain fiber induced by fluctuation of the input laser signal power, as well as reduce potential photodarkening at the input of the gain fiber.

Systems, apparatus, and methods for laser amplification in fiber amplifiers

A method and apparatus for providing a high peak power optical beam. The method includes interleaving pulse trains of different wavelengths and spatially and temporally overlapping the different wavelengths to produce an amplified output beam with very high peak power.

High peak power optical amplifier

Coherent beam combining of laser gain elements achieves high output power in a diffraction limited beam. An active beam combining system coherently combines optical beams emitted by semiconductor laser gain elements in an external resonant cavity configuration. A beam combiner in the resonant cavity combines the outputs of the laser gain elements into a single coherent output beam whose power is monitored by a photodetector. A processor uses the photodetector's output to adjust the phases of the respective optical beams emitted by the laser gain elements so as to increase or maximize the coherent output beam's power. The processor may vary the optical beams' phases according to a stochastic parallel gradient descent (SPGD) algorithm for active phase control. Experimental results show a beam combining efficiency of 81% with an upper limit of 90% or higher and without the scaling limits imposed on passive-phasing systems.

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Acton, MA, United States of America

Steven J Augst