Multi-frequency High Power Microwave Generation and Amplification via Optically Gated Electron Beams
Abstract
This proposal provides novel theoretical modeling of multi-frequency high power microwave (HPM) generation and amplification by optically gated electron beams. Benchmark of the theory with recent experiments and simulations is sought. The objective is to provide a foundational understanding of the underlying physics in optically gated electron emission and its interaction with microwave circuits. The goal is to provide a guideline for the design of compact HPM devices with the ultimate high power output and extremely flexible frequency tunability.Traveling wave devices utilize collective interaction of an electron beam with a periodic structure to convert electron beam energy into electromagnetic radiation. They are key elements in telecommunication systems, satellite-based transmitters, military radar, communication data links, and electronic countermeasures. Relying on the velocity modulation of the electrons by an input microwave signal, traveling wave amplifiers typically exhibit inevitable velocity dispersion, substantial delay for gain production, and intrinsic launching loss of the input signal. Therefore, it is of great interest to explore direct density modulation for traveling wave devices. In this proposal, we will explore density modulation in optically gated electron emission. This is motivated by the recent rapid development in ultrafast lasers and photonics, which has opened up unprecedented advances to control electron beam dynamics at ultrashort spatial-temporal scales. Optically gated electron beams due to pulsed laser would potentially provide femtosecond scale precision in phase-control of electromagnetic signals from traveling wave devices. Selective optical gating of individual emitters in an emitter array would enable different density modulations simultaneously, thus providing strong flexibility for HPM applications. The proposal focuses on several fundamental issues on the modulation of high current electron emission due to optical gating, and the interaction of thus premodulated electron beams with electromagnetic circuits and structures, based on the investigators extensive experiences on ultrafast electron emission, diode physics, and beam-circuit interaction. We propose to develop general quantum theories for laser-induced (or assisted) electron emission for arbitrary combination of thermionic-field-photo- emission mechanisms. Issues such as electron beam density profile control, space charge effects, and beam transport will be investigated. We will conduct a detailed study on the interaction of the premodulated beams with slow wave circuits, along with the evaluation of threshold current and device performance. We will explore novel methods to push the operating limits for HPM devices, including multi-frequency coupling and multiple-beam excitation. New physics, such as Fano resonance in HPM interactions will be studied, which could enable unconventional ways to control HPM generation and amplification. Useful scaling laws are expected to emerge from these theoretical and computational studies, thus providing guidelines for the development of advanced compact HPM devices. The proposed research on implementing both high power and frequency tunability in HPM devices will provide Navy and DOD a critical disruptive capability using high power microwaves. The theory will also be valuable to neighboring fields such as novel miniaturized electromagnetic radiation sources, nano-optoelectronics, ultrafast physics, material science, and accelerator technology.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jun 17, 2020
- Source ID
- N000142012681
Entities
People
- Peng Zhang
Organizations
- Michigan State University
- Office of Naval Research
- United States Navy