PROBLEM TO BE SOLVED: To observe a sample with high contrast in the observation of an observation range containing a region where a sample is present and a region where the sample is not present. SOLUTION: This observation method includes the step of irradiating the observation range containing the sample A with a pulselike terahertz wave L2to apply the first electromagnetic wave L2, which is reflected from or transmitted through the observation region, and a pulselike second electromagnetic wave L1, of which the wavelength is shorter than that of the terahertz wave L2, to an optical crystal 8 and the step of detecting the second electromagnetic wave L1emitted from the optical crystal 8. The second electromagnetic wave L1is applied to the optical crystal 8 in the timing arranged to a phase wherein one of the electric field amplitude of the first electromagnetic wave L2reflected from or transmitted through the sample A present in the observation region and the electric field amplitude of the first electromagnetic wave L2reflected from or transmitted through a region other than the sample A in the observation range becomes larger than the other one of them. COPYRIGHT: (C)2011,JPO&INPIT
