TERAHERTZ AREA DIELECTRIC DISPERSION DETERMINING METHOD BY FEMTO-SECOND ULTRA-SHORT VISIBLE LIGHT PULSE

摘要

PROBLEM TO BE SOLVED: To determine the dielectric constant in the tetrahertz area of a nonlinear optical crystal with a specific equation without using an optical system for far infrared rays by introducing the dielectric constant in the tetrahertz area from the transient response induced by pulses of ultra-short visible light. SOLUTION: The response of a sample is observed by the transient diffraction grating method. A well-known optical system used by the grating method can be used for the optical system. When two ultra-short light pulses are crossed in the sample, the sample is excited in a spatially periodic structure. When another ultra-short light pulse is fed, it is diffracted by the grating. The intensity of the diffracted light is recorded while the incidence time of this ultra-short light pulse is changed through a delay optical path, and the aging effect (responsiveness) of the grating is outputted. Such a vibration wave-form b(t) is determined that the square b(t)<2> of its responsiveness reproduces the observed vibration component. The vibration wave-form b(t) is Fourier-transformed into b(ω). When b(ω) is substituted in the left side of the equation (1), the frequency dependencyε(ω) of the dielectric constant is obtained.