Terahertz wave spectroscopic measurement apparatus and terahertz wave spectroscopic measurement method

A terahertz wave spectroscopic measurement method for performing a terahertz wave spectroscopic measurement on a measurement object by branching pulsed laser light output from a light source by a branching unit to output pump light and probe light, generating and outputting a terahertz wave by a terahertz wave generation element by inputting the pump light, and detecting a correlation between the terahertz wave passed through the measurement object and the probe light by a terahertz wave detection element, the method comprising:

• arranging a prism configured to have an input surface, an output surface, and an arrangement surface, and a measurement auxiliary member configured to have an input-output surface and a total reflection surface, on an optical path of the terahertz wave such that the input-output surface of the measurement auxiliary member faces the arrangement surface of the prism, and arranging the measurement object on the total reflection surface of the measurement auxiliary member;
• propagating the terahertz wave output from the terahertz wave generation element and input to the input surface of the prism in the inside of the prism from the input surface to the arrangement surface, and then, propagating the terahertz wave in the inside of the measurement auxiliary member from the input-output surface to the total reflection surface to totally reflect the terahertz wave by the total reflection surface of the measurement auxiliary member;
• and
• propagating the totally-reflected terahertz wave in the inside of the measurement auxiliary member from the total reflection surface to the input-output surface, and then, propagating the terahertz wave in the inside of the prism from the arrangement surface to the output surface to output the terahertz wave from the output surface of the prism to the terahertz wave detection element, wherein
• in the terahertz wave spectroscopic measurement, the measurement object is irradiated with an evanescent component generated at the time of total reflection of the terahertz wave on the total reflection surface of the measurement auxiliary member for acquiring information on the measurement object, and
• the measurement auxiliary member of which a thickness or a refractive index is set such that a main pulse, which is a pulse of a terahertz wave totally reflected by the total reflection surface of the measurement auxiliary member without being multiply-reflected inside any optical element on an optical path of the terahertz wave, and a noise pulse, which is a pulse of a terahertz wave multiply-reflected inside any optical element on the optical path of the terahertz wave and reflected on an interface between the prism and the measurement auxiliary member, are temporally separated from each other when detecting the correlation by the terahertz wave detection element is used.