This proposal is directed towards the development of the time-domain spectroscopy (TDS), which allows us to detect the electric field itself. The TDS is a powerful method for material science, because it provides us many advantages, e.g. simultaneous estimation of real and imaginary parts of the dielectric function of the material. Thus the TDS is superior to conventional IR spectroscopy using a monochromator or a Fourier interferometer. However, the detection limit of the TDS is usually THz and much lower than that covered with a conventional FTIR. To push the limit to higher frequency regions, e.g. mid- or near-infrared (IR) region, we have used photoconductive (PC) antennas and ultrashort laser pulses. Recently, we measured ultrabroadband infrared wave generated by optical rectification with a GaSe crystal. Figure 1 shows an example of the temporal profile of the electric field detected with the PC antenna. Here a mode-locked Ti:sapphire laser with approximately 10 fs width was used for the generation and detection of the ultrabroadband infrared waves. The Fourier transformed spectrum of the temporal profile Fig. 1 is shown in Fig. 2. Ultrahigh frequency component up to 100THz was successfully detected. Moreover, we confirmed that the same PC antenna enables us to detect the ultrabroadband electric field from 0.1 to 100THz. This means that the PC antenna detection is a promising technique for spectroscopy in far- and mid-IR regions. Now we are trying to expand the detection limit towards near-IR or optical region using a combination of a sub-10fs laser system and a newly designed micro-fabricated PC antenna. This novel detection method is also applicable to optical communication technologies.