Abstract
Abstract
We investigate the hot electrons generated from two-plasmon decay (TPD) instability driven by laser pulses with intensity modulated by a frequency Δω
m
using theoretical and numerical approaches. Our primary focus lies on scenarios where Δω
m
is on the same order of the TPD growth rate γ
0 (
Δ
ω
m
∼
γ
0
), corresponding to moderate laser frequency bandwidths for TPD mitigation. With Δω
m
conveniently modeled by a basic two-color scheme of the laser wave fields in fully-kinetic particle-in-cell simulations, we demonstrate that the energies of TPD modes and hot electrons exhibit intermittent evolution at the frequency Δω
m
, particularly when
Δ
ω
m
∼
γ
0
. With the dynamic TPD behavior, the overall ratio of hot electron energy to the incident laser energy,
f
hot
, changes significantly with Δω
m
. While
f
hot
drops notably with increasing Δω
m
at large Δω
m
limit as expected, it goes anomalously beyond the hot electron energy ratio for a single-frequency incident laser pulse with the same average intensity when Δω
m
falls below a specific threshold frequency Δω
c
. This anomaly arises from the pronounced sensitivity of
f
hot
to variations in laser intensity. We find this threshold frequency Δω
c
primarily depends on γ
0 and the collisional damping rate of plasma waves, with relatively lower sensitivity to the density scale length. We develop a scaling model characterizing the relation of Δω
c
and laser plasma conditions, enabling the potential extention of our findings to more complex and realistic scenarios.
Funder
National Natural Science Foundation of China
Strategic Priority Research Program of Chinese Academy of Sciences