Detecting coherent radiation on the far-field plane?

[HaoPengYY]

Dear Developers, Hi. Thanks for your wonderful code. I like the classical radiation module, which allow me to calculate far-field radiation during complex PIC simulation of laser plasma interaction. I notice that we can dump the far-field radiation as E(omega), not |E(omega)|, which is to say we can get both the real part and imaginary part of radiation spectrum. So does that mean one can do inverse Fourier transform to E(omega), then get the temporal profile of the radiation as E(t)? I know that for an incoherent radiation, this is meaningless. But for the coherent radiation as shown by J. Vieira et al in Generalized Supperadiance, if the right E(omega) is calculated, we should be able to get the right temporal shape of the coherent radiation on the far-field plane, right?

[HaoPengYY]

Actually, to calculate the temporal field of an incoherent radiation is not necessary meaningless. For example, the Compton/Thomson scattering of a relativistic electron bunch with a laser with angular momentum(spin angular momentum/circular polarization, orbital angular momentum(OAM)/twisted Lagurre Gaussian) can generate high energy X/γ rays with OAM. For references, please see Compton scattering with LG,, Thomson scattering with CP laser and LG laser, Thomson scattering with CP laser We can compute the angular momentum density by knowing E(t). We should be able to reproduce the simulations in the references mentioned-above.

[sbastrakov]

Hello @HaoPengYY , thanks for your suggestion and the links. @PrometheusPi @finnolec could you comment on this?

[PrometheusPi]

Dear @HaoPengYY , please excuse the long silence. You are totally right. In principle you can reconstruct your source distribution if you have your complex radiation. Thus with the complex radiation data in our openPMD based radiation output this is possible. (There might be some numerical noise effects since you are summing billions of particles and thus will have some rounding errors.)

Yes, incoherent radiation is also very interesting. Most applications (Thomson sources) are currently working in this regime. Yes, these publications could be reproduced with the radiation plugin of PIConGPU.