Ring laser gyroscope

Abstract: We report the demonstration of a Sagnac-effect atom interferometer gyroscope which uses stimulated Raman transitions to coherently manipulate atomic wave packets. We have measured the Earth's rotation rate, and demonstrated a short-term sensitivity to rotations of $2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}8}(\mathrm{rad}/\mathrm{s})/\sqrt{\mathrm{Hz}}$.

Abstract: This paper presents a review of both active and passive ring laser devices. The operating principles of the ring laser are developed and discussed, with special emphasis given to the problems associated with the achievement of greater sensitivity and stability. First-principle treatments of the nature of quantum noise in the ring laser gyro and various methods designed to avoid low-rotation-rate lock-in are presented. Descriptions of state-of-the-art devices and current and proposed applications (including a proposed test of metric theories of gravity using a passive cavity ring laser) are given.

Abstract: An automobile collision avoidance system based on laser radars is disclosed for aiding in avoidance of automobile collisions. The very small beam width, very small angular resolution and the highly directional character of laser radars provide a plurality of advantages as compared with microwave radars. With two sets of laser radars this system can detect the location, the direction of movement, the speed and the size of all obstacles specifically and precisely. This system includes laser radars with transmitters and receivers, a computer, a warning device and an optional automatic braking device. A steering wheel rotation sensor or a laser gyroscope is utilized to give information of system-equipped vehicle's directional change. The system will compare the predicted collision time with the minimal allowable time to determine the imminency of a collision, and when determined, provides a warning. An optional automatic braking device is disclosed to be used when the vehicle user fails to respond to a warning. Furthermore, a wheel skidding detecting system based on a discrepancy between the directional change rate predicted by a steering wheel rotation sensor and the actual directional change rate detected by a laser gyroscope is also disclosed. The detection of wheel skidding can be utilized by various vehicle control designs. An averaging device for a steering wheel and a vehicle tilting sensor are used to supplement the steering wheel rotation sensor to improve the accuracy of the automobile collision avoidance system and the wheel skidding detecting system.

Abstract: We reports improvements to our Sagnac effect matter-wave interferometer gyroscope. This device now has a short-term rotation-rate sensitivity of 6×10−10 rad s−1 over 1 s of integration, which is the best publicly reported value to date. Stimulated Raman transitions are used to coherently manipulate atoms from counterpropagating thermal beams, forming two interferometers with opposite rotation phase shifts, allowing rotation to be distinguished from acceleration and laser arbitrary phase. Furthermore, electronically compensating the rotation-induced Doppler shifts of the Raman lasers allows operation at an effective zero rotation rate, improving sensitivity and facilitating sensitive lock-in detection readout techniques. Long-term stability is promising but not yet fully characterized. Potential applications include inertial navigation, geophysical studies and tests of general relativity.

Abstract: A new method of measuring inertial rotation is presented. It is based on the use of a passive ring resonator as the rotation sensing element and an external laser for measuring the difference between the clockwise and counterclockwise lengths of the resonator. Preliminary performance data is included.