Recent progress in laser terahertz emission microscopy toward high-resolution imaging

A laser terahertz emission microscope (LTEM) technique has become a valuable tool for both of basic science and industrial applications. Because THz radiation properties from semiconductor show physical information including carrier dynamics and thus its mapping allows us to visualize the local electric fields in semiconductor integrated circuits nondestructively. We report recent progress in LTEM techniques. For high spatial resolution, we designed the experimental setup of our LTEM with a beam expander and a high numerical aperture objective lens. To evaluate the spatial resolution, we carried out THz-radiation imaging of test samples such as Au strip lines with various distances from 0.5 μm to 10 μm fabricated on InP substrate and the integrated chip of operational amplifier under the irradiation of femtosecond laser pulse with wavelength 780 nm. In this system we could distinguish 1.5 μm lines and space structure at zero bias condition.