Third harmonic generation from InSb excited by Free Electron Laser

Using intense beam with frequency 4 THz from Free Electron Laser to pump the InSb crystal, we obtained strong third harmonic generation (THG) with efficiency up to 4 ×10
^-4
at room temperature. The THG can originate from the nonlinear third order electric current due to non-parabolicity of the band structure in InSb. InSb yields significantly higher THG signal compared with InAs whose shape of energy band structure is more parabolic. The THG signal increases up to 2.5 times at 370 K due to the increase of the free carrier.