Abstract
The interaction of an electromagnetic wave with a relativistic ionization front with frequency up-conversion has been demonstrated by the particle-in-cell (PIC) method. In the PIC simulation, the plasma ionization front is formed by using an electron beam ionizing the background gas. The PIC results are in good agreement with the basic analytic theory. In addition, the charged particles are modulated in the interaction area observed in the PIC simulation, which is hardly obtained by other methods. Based on the verified PIC methods, a relativistic hollow ionization front for frequency up-conversion of microwave to terahertz radiation is proposed for increasing the reflection cross section. Finally, the reflected energy can be increased by at least 3 orders of magnitude compared to the traditional methods.
Highlights
The reflection of the electromagnetic wave from a moving boundary gives rise to the well-known relativistic Doppler shift, and both its frequency and its duration are altered.1 This mechanism may be exploited to transform the frequency spectrum of an incident pulse and provide tunable radiation from millimeter to ultraviolet wavelengths as well as subfemtosecond pulse lengths.2–5 The moving boundary can be realized with an electron beam,6 a rapidly expanding plasma,7 an optically excited silicon substrate,8 or electron density modulations in a wakefield.9,10 To achieve an appreciable frequency upshift factor, the moving boundary must propagate close to the light speed, c
We enable the impact ionization model to create the plasma in the room temperature gas having a pressure of 10 mTorr
The electron current determines the number of electrons emitted per unit time and per unit area, so it meets IF ∝ Np
Summary
The reflection of the electromagnetic (em) wave from a moving boundary gives rise to the well-known relativistic Doppler shift, and both its frequency and its duration are altered. This mechanism may be exploited to transform the frequency spectrum of an incident pulse and provide tunable radiation from millimeter to ultraviolet wavelengths as well as subfemtosecond pulse lengths. The moving boundary can be realized with an electron beam, a rapidly expanding plasma, an optically excited silicon substrate, or electron density modulations in a wakefield. To achieve an appreciable frequency upshift factor, the moving boundary must propagate close to the light speed, c. It has advantages of simulating complex structures with PIC methods At present, it seldom studies the gas ionization by an intense optical pulse from the first principle, while an equivalent PIC model for the impact ionization of the background gas to generate a plasma front with a relativistic electron beam is proposed. It seldom studies the gas ionization by an intense optical pulse from the first principle, while an equivalent PIC model for the impact ionization of the background gas to generate a plasma front with a relativistic electron beam is proposed This model is sufficient because the core idea of this paper is to simulate a hollow plasma front. Frequency up-conversion of microwave to terahertz radiation by a relativistic hollow ionization front is demonstrated
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