Programmable Time-Varying Spectral Encoding for Advanced Control of High-Energy, High-Power Laser Systems

Daniel Mittelberger | 21-ERD-034

Project Overview

There is growing demand from high-energy high-peak-power laser facility users for user-defined sub-structured laser pulses to mitigate or optimize laser-matter interactions. These patterned pulses would have a wide range of applications including mitigation of cross beam energy transfer (CBET) and laser plasma instabilities (LPI) on high energy density science (HEDS) and inertial confinement fusion (ICF) experiments, mitigation of stimulated rotational Raman scattering (SRRS) in directed energy applications, optimization of plasma optic/beam combination experiments, dynamic focal spot steering for ICF, flying focus to chase imploding targets in direct drive ICF, and optimization of laser machining. However, there are few technologies that can produce high-energy patterned laser pulses with time-dependent amplitude, wavelength, pointing, and/or focusing at the relevant picosecond timescales.

We developed a direct space-to-time pulse shaping technique, called Space-Time Induced Linearly Encoded Transcription for Temporal Optimization (STILETTO), that generates 1000+ independent temporal features over a span of up to 1 ns. The amplitude and wavelength can be independently set at each point in time. To validate the pulse shape, a novel spectral interferometry technique was developed to measure the power and instantaneous wavelength of the generated laser pulses. This system was unique compared to other spectral interferometers by achieving high fidelity & dynamic range with single shot capability, had >1 ns record, used a 3x3 polarization-maintaining (PM) splitter to achieve three reference phase shifts, and had very advanced signal processing to reduce or eliminate distortions in the recovered signal. Finally, the pulse shaper and optical recorder were integrated to iteratively optimize the generated shape to the users desired waveform. The demonstrated closed-loop shapes reveal a high technology readiness level for this technology. The full closed-loop shaping system is being deployed on the Jupiter Laser Facility for users to perform experiments.

Mission Impact

The proposed work aligned with Lawrence Livermore National Laboratory strategic focus areas in stockpile stewardship and inertial fusion energy. It further aligned with the Institutional Science Capability Portfolio (ISCP) investment strategy in the following areas:

1. High Energy Density Science and inertial confinement fusion: dynamic pointing and flying focus for HEDS plasma mitigation and ICF enhancement;

2. Development of Core Competencies in Laser and Optical Science and Technology of ultrafast diagnostics and ultrafast shaped pulses;

3. Laser-matter interactions, where picosecond level control and measurement is required;

4. Directed energy, for concepts for rapid control of laser beams and propagation in air;

5. Laser machining and additive manufacturing applications.

Publications, Presentations, and Patents

Muir, Ryan D., John H. Heebner, and Daniel E. Mittelberger. THREE PHASE SPECTRAL INTERFEROMETRY (3PSI). U.S. Nonprovisional Patent Application 18/047,120, filed 17 October 2022.

R. D. Muir, D. E. Mittelberger, J. E. Heebner, "Laser pulse shaping at Jupiter Laser Facility: Programmable Time-Varying Wavelength and Amplitude for Advanced Control of High Energy/High Power Laser Systems" (Presentation, NIF and JLF User Group Meeting, Livermore, CA, Feb 21-23, 2023).

D. E. Mittelberger, R. D. Muir, J. E. Heebner, "STILETTO: a novel technique for ps-to-ns optical power and wavelength encoding" (Presentation, SLAC LCLS-MEC Group Meeting, Menlo Park, CA, Feb. 9, 2023).

Mittelberger, D.E., R. D. Muir, and J. E. Heebner. "Dynamic wavelength control of laser pulse profiles at picosecond to nanosecond timescales." Opt. Express 30, 1875-1884 (2022).