Quantum Radiation in Ultra-Intense Laser Pulses

Abstract

The theoretical framework for describing the emission by free charged particles, scattered from highly intense laser fields, is extended to arbitrary temporal shapes of the scattering laser field. This work is motivated by the recent trend of laser technology, to achieve highest laser intensities by a tight temporal compression of the laser energy, down to only a few cycles of the carrying electromagnetic wave. Since modern laser fields are inaccessible to the perturbative treatment of usual QED, they are described as unquantized external fields and taken into account exactly. The emission of one or two photons are particularly studied. For both processes a powerful analytical approximation is formulated, valid in the experimentally relevant regime of high laser intensities and electron energies. This technique foreshadows possible applications, such as a viable way of determining the absolute phase of a highly intense few-cycle laser pulses, which was an unresolved problem so far. Furthermore it is demonstrated how the usually strongly suppressed signal from two photon emission can be reliably discriminated from the dominant single photon emission signal. Finally analytical solutions for two hitherto unresolved issues are presented: Describing the spatial focusing of a fewcycle laser pulse and solving the Dirac equation in the presence of a focused laser beam.In connection with the work on this thesis, the following articles were published in refereed journals:

Nonlinear single Compton scattering of an electron wave packet

“…is exactly what we observe in Fig. 6, where different curves direction is the forward direction and that the angular emission range of the electron along the magnetic field of the laser is of about m/ε, whereas along the electric field of the laser, the electron emits up to angles of the order of mξ/ε [48]. It is also worth observing the large oscillations in the emitted intensity between successive peaks when varying p x (top part of Fig.…”

“…Apart from exhibiting the already mentioned shift of the peak frequencies as one of the transverse components varies, we also observe that by varying p y by about 1-2 electron masses the spectrum is significantly suppressed. The reason is that the observation direction is the forward direction and that the angular emission range of the electron along the magnetic field of the laser is of about m/ε, whereas along the electric field of the laser, the electron emits up to angles of the order of mξ/ε [48]. It is also worth observing the large oscillations in the emitted intensity between successive peaks when varying p x (top part of Fig.…”

“…where q µ is a four vector such that q − = p − − k ,− , q x,y = p x,y − k x,y and q + = (q 0 + q 3 )/2 = (m 2 + q 2 x + q 2 y )/2q − (q 2 = m 2 ). Equation ( 19) can be easily identified as the incoherent average over the modulus squared of ρ(p) of the well-known expression of the differential angular energy emission rate for a nonlinear single Compton scattering event of an electron with definite initial four-momentum p µ and final four-momentum q µ [14, 18,48]…”

Nonlinear dynamics of a charged particle in a strong non-null knot wave background

“…We will follow the general approach from [57,58]. (For a recent review of the strong-QED see [62]. )…”

“…After fixing the gauge, the system can be quantized by using the canonical quantization method [58,61,62]. To this end, we impose the canonical commutation relations on the fields {ψ, ψ, A µ } and their canonically conjugate momenta {π = iψ † , π = 0,…”