Generation of Relativistic THz Radiation by Laser Irradiation of Microplasma Waveguide with Application to Pulsed Polarimetry

Generation of relativistic pulses in the terahertz range and its application to pulsed polarimetry is proposed.~~Irradiation of a microplasma waveguide (MPW) with a relativistic (a0\textgreater 1) p-polarized sub-pico second laser results in~a~high-charge (10s nC) electron bunches with~energies~up to 100 MeV.~~As~an~electron bunch exits the MPW~its~energy is converted to THz radiation through coherent diffraction radiation.~~Particle-in-cell (PIC) simulation is used to demonstrate the generation of the electron bunches by laser irradiation of~a~plasma~at~grazing and oblique incidences~to~a sharp plasma-vacuum boundary.~~The~spacing of the electron bunches~is roughly one laser wavelength.~~We shall discuss the various competing mechanism facilitating~their~generation: direct laser transverse field driver, ponderomotive force, counter streaming (return current) electrons in the plasma.~~Moreover, we shall demonstrate the THz radiation generation by performing spectral analysis of the exiting radiation.~~2D PIC simulation shall be used to optimize the MPW shape and laser properties to maximize the outgoing THz radiation.~~Lastly, we shall discuss how the THz radiation is applicable to pulsed polarimetry to enable the measurement of internal magnetic field.