Apparatus and method for acquiring time waveform of terahertz waves

A method for acquiring an accurate time waveform of terahertz waves using an apparatus including a generating portion which generates terahertz waves, a detecting portion which detects the terahertz waves, a first delay portion which changes a difference in length of the optical paths of excitation light beams radiated to the generating portion and the detecting portion, and a second delay portion which changes a difference between times taken for the excitation light beams to reach the generating portion and to reach the detecting portion, the method comprising:

• acquiring a first time waveform by using the first delay portion with a first difference in length of the optical paths;
• using the second delay portion to change the first difference in length of the optical paths to a second difference in length of the optical paths that is different from the first difference in length of the optical paths;
• acquiring a second time waveform by using the first delay portion with the second difference in length of the optical paths;
• adjusting the acquired first and second time waveforms in accordance with a predetermined difference in length of the optical paths based on the first and second differences in length of the optical paths;
• and
• averaging the first and second time waveforms according to the predetermined differences in length of the optical paths to supply the accurate time waveform.