The principle of a laser gyro is to measure the angular velocity of rotation (the Sagnac effect) using the optical path difference. In the closed optical path, the two beams of light and light transmitted by the same source in the clockwise direction and the counterclockwise direction interfere with each other, and by detecting the phase difference or the change of the interference fringes, the rotational angular velocity of the closed optical path can be measured. The basic component of a laser gyro is a ring laser consisting of a closed optical path made of triangular or square quartz with one or several tubes filled with a mixed gas (helium gas), two opaque mirrors and A semi-transparent mirror. The mixed gas is excited by a high frequency power source or a direct current power source to generate a monochromatic laser. To maintain loop resonance, the perimeter of the loop should be an integer multiple of the wavelength of the light. The laser is led out of the loop by a semi-transparent mirror, and the two oppositely transmitted lasers are interfered by the mirror, and the digital signal proportional to the output angle is input through the photodetector and the circuit.
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