Compact High Efficiency Electrically Tunable Amplifier (CHEETAh)

Project Overview

The goal of this project was to develop a new type of optically triggered, high-speed and high-power switch for radiofrequency applications with potential to exceed current state-of-the-art power and bandwidth. This device operates under a new operation principle, where discrete packets of charge carriers are generated with defined size. These are then swept out of the device at high enough fields to prevent diffusion and expansion of these packets. Individual pulse width is determined by the spatial extent of the packets and their drift velocity, which would enable control over both amplitude and frequency by control of the initial packet size, illumination intensity, and applied voltage. This effort demonstrated this new mode of operation while uncovering a new regime of pulse compression using negative differential mobility (NDM) semiconductors such as GaAs, where the output electrical pulse is substantially shorter than the input optical pulse.

Mission Impact

Technology developed on this project has applicability to directed-energy missions as well as advanced-materials core competency. The new physics regime has increased understanding of high-power/high-speed RF materials and devices used in DE missions. Much of the experimental techniques and capability developed under this LDRD have been leveraged to advance other high-power RF technologies under development at LLNL.

Publications, Presentations, and Patents

Voss, L. et al. 2021. "Pulse Compression Photoconductive Semiconductor Switches." Published patent US20220123211A1.

Voss, L. et al. 2021. "High-Power Electrically Tunable Switch." Published patent US20210336131A1.

Rakheja, S. et al. 2020. "Performance Modeling of Silicon Carbide Photoconductive Switches for High-Power and High-Frequency Applications." IEEE Journal of the Electron Devices Society 8, 1118-1128 (2020); doi: 10.1109/JEDS.2020.3022031.

Rakheja, S. et al. 2020. "Modeling and Design of SiC-Based High-Frequency Photoconductive Switches." 4th IEEE Electron Devices Technology & Manufacturing Conference (EDTM), January 2020; doi: 10.1109/JEDS.2020.3022031.

Milestone, W. et al. 2021. "Monte Carlo Transport Analysis to Assess Intensity Dependent Response of a Carbon-Doped GaN Photoconductor." Journal of Applied Physics 129 (19), 195703 (2021); doi.org/10.1063/5.0040173.

Rakheja, S. et al. 2021. Design and Simulation of Near-Terahertz GaN Photoconductive Switches-Operation in the Negative Differential Mobility Regime and Pulse Compression." 2021. IEEE Journal of the Electron Devices Society 9, 521-532 (2021); doi: 10.1109/JEDS.2021.3077761.

Dong, Y. et al. 2022. "Design Considerations for Gallium Arsenide Pulse Compression Photoconductive Switch." Journal of Applied Physics 131, 134504 (2022); doi.org/10.1063/5.0083672.

Mukherjee, S. et al. 2022. "A Prony-Based Curve-Fitting Method for Characterization of RF Pulses from Optoelectronic Devices." IEEE Signal Processing Letters 29, 364-368 (2022); doi.org/10.1109/LSP.2021.3135795.