Relativistic second-harmonic generation of a laser from underdense plasmas

Summary form only given. A high intensity laser obliquely incident on a vacuum-plasma interface produces second-harmonic radiation in the reflected component. The efficiency of second-harmonic generation increases with the angle of incidence, up to critical angle of incidence (our model is not valid beyond critical angle of incidence). Efficiency also depends on electron density, showing a maximum at /spl omega//sub p//sup 2///spl omega//sup 2/=0.7, where /spl omega//sub p/ and /spl omega/ are relativistic plasma frequency and laser frequency respectively. The efficiency of second-harmonic generation increases sharply with laser intensity in the non-relativistic regime and saturates at higher intensities. The intensity of the second-harmonic is proportional to square of the laser intensity at low pump laser intensities and tends to proportional to laser intensity in the strong relativistic regime.