PURPOSE: To obtain two-wavelength displacement interferometer which assures long-term measuring accuracy by controlling the wavelength of at least one of two different light waves so as to agree with the wavelength of absorption line of an atoms or a molecule.
CONSTITUTION: A fundamental wave radiated from a semiconductor laser excitation ring Nd;YAG laser 1 is converged into a KTP crystal 2 (KT;OPO4) with a lens 3a. The 2nd harmonics are produced by mutual effect between the fundamental wave and the crystal 2, and then are formed into parallel light together with the fundamental wave which passes the crystal 2 by lens 3b, and the fundamental wave transmitted through a mirror 4 and the 2nd harmonics are used for the light source of an interferometer. The 2nd harmonics reflected by the mirror 4 includes an absorption line which agrees with the wavelength of the 2nd harmonics. The 2nd harmonics passes through a container 5 in which the gas of an iodine molecule I2 is filled and then is incident upon a light detector 6. The transmitted light intensity of 2nd harmonics which is changed with the absorption of the gas of an iodine molecule is measured in the light detector 6, and the measured signal is processed in a signal processing systems 7. The oscillation wavelength of the laser 1 is controlled by using the signal.
UCHIKAWA KIYOSHI
ISHIDA AKIRA
