Fig. 1. Comparison between the results of nonlinear (NLC) and inverse (ICS) Compton scattering in the collision between an electron with η = 0.2 and a 16-cycle laser pulse with intensity ξ₀ = 0.1 and rotation c=+1. (a) and (b) 2D photon spectra d²P/ds dθ from an unpolarized electron calculated using (16a) and (18a), respectively. The black dashed curves correspond to the linear Compton line s_l = 2η/(2η + 1 + r²) for laser carrier frequency v = 1. (c) Energy spectra dP/ds emitted by an electron with longitudinal spin Ξ_z = 0, ±1. The black dashed line indicates the location of the linear Compton edge s_l,1 = 2η/(2η + 1).

Fig. 2. Polarization transfer from a laser photon to a scattered photon via the linear Compton process (18) of scattering by an unpolarized electron: (a) Γ₁(s, r)/ς₁(v) in a linearly polarized field; (b) Γ₃(s, r)/ς₃(v) in a circularly polarized field. (c) Polarization spectra Γ_1,3(s) of the scattered photon in the linear (a) and circular (b) backgrounds. The same parameters as in Fig. 1 are used, except for the linearly polarized field (c=0).

Fig. 3. (a) Energy spectra and (b) polarization of photons scattered by a high-energy electron with η = 0.2 and different longitudinal spins Ξ_z = 0, ±1 in a circularly polarized laser field with intensity ξ₀ = 1, rotation c=+1, and envelope f(ϕ) = cos²[ϕ/(2N)] if |ϕ| < Nπ and f(ϕ) = 0 otherwise, where N = 16. The black dashed lines indicate the edges of the first three harmonics, sn=2nη/(2nη+1+ξ02), with n = 1, 2, 3. In (a), the inset zooms in the energy spectra around the first harmonic to show the difference between the QED and LMA results.

Fig. 4. (a) Energy spectra and (b) polarization of photons scattered by a high-energy electron in a circularly polarized laser field with intensity ξ₀ = 5. The black dashed lines indicate the edges of the first three harmonics, sn=2nη/(2nη+1+ξ02), with n = 1, 2, 3. The other parameters are the same as in Fig. 3.

Fig. 5. (a) Energy spectra and (b) polarization of photons scattered by an electron with η = 0.2 in a linearly polarized laser field with intensity ξ₀ = 1. The black dashed lines indicate the edges of the first three harmonics, sn=2nη/(2nη+1+ξ02/2), with n = 1, 2, 3. In (a) and (b), the contributions from the electron spin Ξ are too small to show. (c) Longitudinal polarization transfer from incoming electron to scattered photon as a function of photon energy s. The other parameters are the same as in Fig. 3.

Fig. 6. (a) Energy spectra and (b) polarization of photons scattered by a high-energy electron in a linearly polarized laser field with intensity ξ₀ = 5. The black dashed lines indicate the edges of the first three harmonics, sn=2nη/(2nη+1+ξ02/2), with n = 1, 2, 3. In (a) and (b), the contributions from the electron spin Ξ are too small to show. (c) Longitudinal polarization transfer from incoming electron to scattered photon as a function of photon energy s. The other parameters are the same as in Fig. 5.

Fig. 7. Helicity transfer from incoming electron to scattered photon via (a) linear Compton scattering with change in collision energy β and (b) nonlinear Compton scattering with change in laser intensity ξ₀. In (a), an electron with longitudinal spin Ξ_z scatters a circularly unpolarized photon ς₃ = 0. In (b), a linearly polarized laser pulse collides with an electron with η = 0.2 and longitudinal spin Ξ_z. The same laser parameters as in Fig. 5 are used.