Transmission-Mode Scanning Probe Laser Terahertz Emission Microscope

We developed a transmission-mode scanning probe laser terahertz emission microscope (sp-LTEM). Femtosecond (fs) optical pulses are delivered and focused on the sample by an optical fiber probe with a beam diameter of 5 mum. The transmission-mode sp-LTEM system is superior to the conventional reflection-mode sp-LTEM system in the viewpoint of the signal sensitivity because emitted THz waves can be detected without being disturbed by the scanning probe itself. The spatial resolution is experimentally estimated as ~2 mum with the gold line and space patterns on a low-temperature-grown gallium arsenide (LT-GaAs) substrate.