Open AccessGas pressure dependence of microwave pulses generated by laser-produced filament plasmas
Author(s) -
Alexander Englesbe,
Jennifer Elle,
Remington Reid,
Adrian Lucero,
Hugh Pohle,
Matthew T. Domonkos,
Serguei Y. Kalmykov,
K. Krushelnick,
Andreas Schmitt-Sody
Publication year - 2018
Publication title -
optics letters/optics index
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.524
H-Index - 272
eISSN - 1071-2763
pISSN - 0146-9592
DOI - 10.1364/ol.43.004953
Subject(s) - optics , plasma , electric field , physics , laser , microwave , amplitude , waveform , atomic physics , protein filament , terahertz radiation , electromagnetic radiation , pulse (music) , pulse duration , materials science , voltage , detector , composite material , quantum mechanics
The plasma arising due to the propagation of a filamenting ultrafast laser pulse in air contains currents driven by the pulse that generate radiated electromagnetic fields. We report absolutely calibrated measurements of the frequency spectrum of microwaves radiated by the filament plasma from 2-40 GHz. The emission pattern of the electric field spectrum is mapped as a function of air pressure from atmosphere to 0.5 Torr. For fixed laser pulse energy, duration, and focal geometry, we observe that decreasing the air pressure by a factor of approximately 10 3 increases the amplitude of the electric field waveform by a factor of about 40. As the air pressure decreases, the lower frequency components (<10 GHz) increase in amplitude faster than those at higher frequencies (>20 GHz). To the best of our knowledge, this behavior has not been observed before, is not predicted by existing theory, and implies the existence of a radiation mechanism in the plasma distinct from that which emits at terahertz frequencies.