Laser Beam Propagation Through Deep Turbulence

Stephen Ammons | 16-ERD-049


The performance of high-contrast adaptive optics (AO) instruments, e.g., the Gemini Planet Imager (GPI), and lasers that operate at visible wavelengths can be severely hampered by control system latencies and temporal wavefront errors. In astronomical AO systems, temporal errors and delays manifest as high spatial frequency wavefront residuals that scatter light into the controllable region of the point spread function (PSF) and diminish sensitivity to faint planets, an effect that is particularly severe when atmospheric coherence times are short. Solutions proposed include lower latency electronics, deformable mirrors with faster response times, and specialized control algorithms such as predictive control.

We constructed the Low-Latency Adaptive Optical Mirror System (LLAMAS), a 20 kHz AO system, to test these techniques in an integrated, real time, closed loop AO system. With an end-to-end system latency of 110 microseconds, LLAMAS achieved ;an order of magnitude improvement in AO system bandwidth over the current generation of AO systems. Controlling 576 modes at an 8 kHz frame rate, LLAMAS in linear quadratic Gaussian mode achieved measured 0 dB bandwidths exceeding 750 Hz for woofer, tweeter, and tip/tilt modes, making it the fastest published AO system. The system currently maintains greater than 60% Strehl at 1053 nm in fast wind conditions. The low-latency AO technology will improve sensitivity to faint planets by greater than 10x in astronomical AO systems, such as GPI, and will enable AO compensation of rapidly flowing turbulence.

Impact on Mission

Achieving stable imaging and laser propagation through optical aberration is important for a range of applications in astronomy, remote sensing, communications, and national security. This program supports Lawrence Livermore National Laboratory's core competency in laser and optical science and technology to field fully-engineered laser propagation systems and aircraft-based active remote sensing systems for material detection and assessments of treaty compliance. This work also leverages the Laboratory's considerable high-performance computing, simulation, and data science core competency to understand supersonic turbulent flow in aerospace systems.

Publications, Presentations, Etc.

Ammons, S. 2017. "Joint Strong and Weak Lensing Analysis of the Massive Cluster Field J0850+3604." Astrophys. J. 844. doi: 10.3847/1538-4357/aa7c19. LLNL-JRNL-745721.

––– . 2017. "An Optical/Near-infrared Investigation of HD 100546 b with the Gemini Planet Imager and MagAO." Astron. J. 153. doi: m10.3847/153-3881/aa6cae. LLNL-JRNL-745723.

Ammons, S., et al. 2018. "LLAMAS: Low-Latency Adaptive Optics at LLNL." Society of Photo-Optical Instrumentation Engineers Astronomical Telescopes and Instrumentation. 10703. 107031N. LLNL-PROC-754397.

––– . 2018. " Long Range, Low Latency Adaptive Optics System at LLNL ." Directed Energy Professional Society Science & Technology Conference, Destin, FL, April 2019. LLNL-PRES-772807.

Follette, K., et al. 2017. "Complex Spiral Structure in the HD 100546 Transitional Disk as Revealed by GPI and MagAO." Astronomical Journal 153, 264. LLNL-JRNL-717867.

Garcia, E., et al. 2017. "Individual, Model-independent Masses of the Closest Known Brown Dwarf Binary to the Sun." Astrophysical Journal 846, 97. LLNL-JRNL-701044.

Johnson-Groh, M., et al. 2017."Integral Field Spectroscopy of the Low-mass Companion HD 984 B with the Gemini Planet Imager." Astronomical Journal 153, 190. LLNL-JRNL-717865.

Kim, M., et al. 2019. "Processing System Design for Implementing a Linear Quadratic Gaussian (LQG) Controller to Optimize the Real-Time Correction of High Wind-Blown Turbulence." Proceedings of the ICALEPCS Conference, New York, NY, October 2019. LLNL-PROC-792238.

Wilson, M., et al. 2016. "A Spectroscopic Survey of the Fields of 28 Strong Gravitational Lenses: the Group Catalog." Astrophysical Journal 833, 194. LLNL-JRNL-717837.

Wong, K., et al. 2017. "Joint Strong and Weak Lensing Analysis of the Massive Cluster Field J0850+3604." Astrophysical Journal 844, 127. LLNL-JRNL-745721.