High-power lasers are of great interest to the scientific community and to the Department of Defense (DoD). Lasers can be used in a broad range of applications such as communications, sensors, chemical detection, material processing, and manufacturing. High-power lasers are essential to state-of-the-art experiments such as the laser-based inertial confinement fusion generator at the National Ignition Facility (NIF) and the LIGO gravitational wave detector. Modern ground-based telescopes use guidestar lasers to calibrate their adaptive optics in order to obtain clear images through the turbulent atmosphere. One of the most difficult challenges to producing a high-power laser system is maintaining a stable, well-polarized, highly coherent (both spatially and temporally), near-diffraction limited beam quality output.  

At the forefront of solid-state laser technology are fiber amplifiers, which use rare-earth dopants to amplify a laser signal to the desired power levels of the application.  Sometimes optical nonlinearities are leveraged to obtain otherwise difficult-to-achieve output wavelengths. These amplifiers are operated at the edge of extremely deleterious optical and thermal nonlinearities that rapidly degrade beam quality, system efficiencies, and can even permanently damage the fibers and optical equipment of the system itself. There is still a large trade-space of fiber designs and amplifier configurations to be explored to overcome these nonlinearities. For example, new microstructure fiber designs are currently being explored both computationally and experimentally. The size, spacing, arrangement, and symmetry of these embedded microstructures can be used optimize the desired amplifier performance, e.g., differential mode loss, robust single-mode operation, polarization maintenance, and thermal sensitivity. High fidelity, predictive computer modeling is essential in the design process given the great cost and manpower effort needed to produce new microstructure fibers. Moreover, all fibers types are susceptible to manufacturing inconsistencies and to sensitive bend losses that are also thermally dependent. Proper uncertainty quantification of the fiber designs, accounting for typical fabrication tolerances, and poorly known fiber properties can greatly enhance the confidence in model predictions.

In order to achieve even greater output powers from a laser system, multiple laser sources can be, either coherently or incoherently, beam combined together into a single beam. Many beam combining schemes have been proposed, some that combine in the near field, others on-target in the far field. There is also the option to passively combine, or to include an active control loop. However, many of these proposed methods have never been tested with high-power laser sources, where thermal issues, small instabilities or noise in the sources, and/or ultra-high intensities may render the beam combining approach ineffective. Additionally, the interaction of the beam combining mechanism and the full beam control/beam director system, which itself may have nonlinear control loops, remains largely unexplored. Experiments in this area are also prohibitively expensive, and time consuming endeavors. Thus, theoretical, analytical, and simulation techniques are highly valuable. 

There are opportunities in these fields for mathematicians, physicists, electrical, mechanical, and optical engineers, and computer scientists.

key words

Fiber amplifiers; Spectral beam combining; Coherent beam combining; Nonlinear optics; Electromagnetics; Light propagation; Microstructure fibers; Elastodynamics; Machine learning; Artificial intelligence; Nonlinear control; Uncertainty quantification

Citizenship:  Open to U.S. citizens

Level:  Open to Postdoctoral and Senior applicants