FIELD: investigating or analyzing materials. ^ SUBSTANCE: device comprises continuously operating laser, three identical cells (heterodyne and signal) with the substance to be analyzed in the Fabry-Perot interferometer. The signal cells are mounted at the quadrupoles exited by a high-frequency generator of sine-cosine voltage with rotation of transverse electric fields in opposite directions. The polaroids crossed to the laser radiation follow the Fabry-Perot interferometer in the optical circuit. The device also has an optical receiver for receiving two signal and heterodyne beams. The optical receiver is connected with the spectrum analyzer. ^ EFFECT: enhanced sensitivity and accuracy. ^ 1 cl, 4 dwg
