Enhancement of THz photomixing efficiency by using a pulse-modulated multimode laser diode

We demonstrate an enhancement of the THz photomixing efficiency by using a pulse-modulated multimode laser diode (MLD). Since the THz output power is proportional to the square of the input laser intensity, the average output THz power can be increased by increasing the peak input laser power and decreasing the duty ratio with the average input laser power kept constant. In the experiment, we show that the efficiency in the photomixing for THz radiation is doubled when we use a pulse- modulated MLD with a duty ratio of 50%. This method provides us an easy way to improve the performance of the photomixing THz system based on a laser diode system.