Generation of tunable, bandwidth controllable terahertz radiation

Tunable radiation in the Fir-THz range is generated by Miniature Photoconducting Capacitor Array [MPCA]. The capacitor array made by deposition of Aluminum structure on semiconductor crystal. The crystal serves as insulation material for the capacitors and as a source for electron-hole plasma during illumination by laser pulse. The illuminating 100 fs 0.8μ laser pulse creates a propagating ionization front inside the crystal volume and sequentially discharges the capacitors. The sequential discharge of the capacitor generates propagating wave inside the plasma. The emitted radiation frequency depends on the energy in the laser pulse and the wavelength of the static wave. In the presented work the tunability was achieved by varying the laser pulse energy from 0.1 to 1 mJ. This results in the free space propagating waves with frequency between 100 GHz and 1.6 THz. The spectrum width is changed according to the static spectrum bandwidth. The concept can be scaled to develop narrowband, tunable, powerful THz source.