Pump beam diameter dependent terahertz generation from surface emitters - experiment and simulation

We report on terahertz wave generation using transient photoconductivity induced by femtosecond laser pulses in semiconductor surfaces. In particular the dependence of terahertz emission characteristics on pump pulse parameters like diameter and input angle is investigated in detail both experimentally and theoretically. It is shown that the emission in forward (quasi-optical reflection) as well as in backward direction (back to the laser) is strongly depending on the diameter of the pump beam on the semiconductor. This is explained in terms of Huygenspsila principle of fundamental waves together with a Hertzian dipole model. The emission properties are simulated using CST MICROWAVE STUDIOreg and compared with experimental results.