Dynamic terahertz emission microscope

One can observe terahertz (THz) radiation from various kinds of materials, when excited with a femtosecond laser, owing to ultrafast current modulation. THz waves reflect various kinds of properties such as local electric field, particularly ultrafast transient phenomena, in their waveforms. The observation of the THz waveforms enables us to explore ultrafast nature of electronic materials and devices as a THz emission spectroscopy. Pump and probe techniques are typical method to study dynamic reposne of optically excited materials. Here we propose to combine laser THz emission microscope (LTEM) with the pum and probe technique to extend the feature of original LTEM. Pump and probe THz emission microscope has been developed with a special resolution of less than 1 μm, and applied for the study of dynamic response of photoconductive antennas made of SI- GaAs, and LT- GaAs. The results revealed that spatial screening effect plays an important role of enhancement of the THz emission near electrodes.