Tunable terahertz radiation from a tunnel ionized magnetized plasma cylinder

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 ωR,ωL=[(2ωp2+ωc2)1/2±ωc]/2, shifted from that without magnetic field at ωp/√(2), where ωp is the electron plasma frequency and ωc 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