Tunable terahertz radiation from a tunnel ionized magnetized plasma cylinder

摘要

A scheme of producing tunable terahertz radiation using a short pulse laser to tunnel ionize a gas jet immersed in a magnetic field is examined. The free electrons born inside the laser pulse retain a finite transverse drift after the passage of the pulse, setting themselves in transverse oscillations at frequencies ω_R,ω_L=[(2ω_p~2+ω_c~2)~(1/2)±ω_c]/2, shifted from that without magnetic field at ω_p/2~(1/2), where ω_p is the electron plasma frequency and ω_c is the cyclotron frequency. The oscillating electron cylinder emits coherent terahertz radiation with ambient magnetic field providing the frequency tunability. The presence of an axial density ripple controls the angular orientation of the emitted radiation.