Impact Statement:Our paper describes a new way to control temporal coherent combination systems, and has potential application to other types of coherent combination and optical phase con...Show More
Abstract:
Coherent pulse stacking (CPS) is a new time-domain coherent addition technique that stacks several optical pulses into a single output pulse, enabling high pulse energy f...Show MoreMetadata
Impact Statement:
Our paper describes a new way to control temporal coherent combination systems, and has potential application to other types of coherent combination and optical phase control as well. Coherent combination is a relatively new field, which is enabling much higher power from fiber and other lasers. Temporal combination is even newer, and applies to pulsed lasers, making high pulse energy fiber lasers possible. Previous work has used preexisting algorithms for electronic control of these combining systems, but we propose and demonstrate a different approach, which can scale to large numbers of pulses without slowing the control system, a bottleneck that other algorithms suffer from. Instead of using just the output peak power for sensing, we use all the available information from the optical system, and process this in a fast and efficient computation on a high speed processing platform.
Abstract:
Coherent pulse stacking (CPS) is a new time-domain coherent addition technique that stacks several optical pulses into a single output pulse, enabling high pulse energy from fiber lasers. We develop a robust, scalable, and distributed digital control system with firmware and software integration for algorithms, to support the CPS application. We model CPS as a digital filter in the Z domain and implement a pulse-pattern-based cavity phase detection algorithm on an field-programmable gate array (FPGA). A two-stage (2+1 cavities) 15-pulse stacking system achieves an 11.0 peak-power enhancement factor. Each optical cavity is fed back at 1.5kHz, and stabilized at an individually-prescribed round-trip phase with 0.7deg and 2.1deg rms phase errors for Stages 1 and 2, respectively. Optical cavity phase control with nanometer accuracy ensures 1.2% intensity stability of the stacked pulse over 12 h. The FPGA-based feedback control system can be scaled to large numbers of optical cavities.
Published in: IEEE Journal of Quantum Electronics ( Volume: 54, Issue: 1, February 2018)
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