Terahertz radiation from imageTe photoexcited by femtosecond laser pulses

Terahertz radiation from image samples excited by femtosecond pulses generated by Ti:sapphire laser was measured by using an ultrafast photoconductive antenna. The radiated terahertz field magnitude was nearly the same for all three investigated alloy compositions with image= 0, 0.2 and 0.3. No azimuthal angle dependence of the radiated signal was detected, which evidences that a linear current surge effect is dominating over nonlinear optical rectification. Experimental observations are discussed in terms of the energy band structure of the investigated compound semiconductors.