investigation of the carrier concentration and laser peak intensity on the terahertz pulse generated by photoconductive antennas

the possibility of terahertz generation has been investigated from a photoconductive switch based on gaas, gated by a femtosecond laser. the emission properties of photoconductive antenna (pca) with low-temperature-grown (lt) gaas have been studied. in such gaas materials presence of the charged defects induces a redistribution of the electric field between the antenna electrodes. this effect has a huge influence on the amplitude of the radiated terahertz field. in this work we demonstrate that carrier concentration enhances radiation power. results obtained as a function of the laser excitation power (with 100 fs rise time and 1khz repetition rate) and carrier concentration are discussed and a comparison of the performance of these devices with a conventional antenna-type (dipole) emitter is given.