Theoretical Modeling And Error Analysis Of Cold Atom Interferometer

Since Chu’s group at Stanford University has demonstrated the first atom interferometry inertial sensor in 1991, the use of cold atom interferometer for inertial measurement has been getting attention increasingly due to its high sensitivity. Many scholars at home and abroad have done deep research on the field for a long time, and have made remarkable achievements. Seeing that most of the published theoretical model is too simple, the paper takes the three-Raman pulse atom interferometer as the research object to study the accurate theoretical model, and the error analysis is carried out, so that this work can provide theoretical guidance for realizing high precision inertial measurement.The concrete works in this dissertation are concluded as follows.1. The theoretical modeling consists two parts. On the one hand, atomic classical trajectory is calculated accurately, the evolution phase and external environment are also considered so that the interference phase can be calculated exactly, making the phase model more precise. On the other hand, the interaction between Raman pulses and atoms was influenced by laser frequency, Rabi frequency, atomic motion, position, etc, which can be summarized as two Raman pulse operators, S and C. Thus the process of atom interferometry can be analyzed by a novel diagrammatic approach, and the output signal can be calculated more convenience and accuracy.2. The Doppler effect in the theoretical modeling of atom interferometry inertial measurement is considered. Through analyzing, we know that the Rabi frequency will change because of excessive detuning caused by Doppler effect and it would lead a series of change to the transition probability, interference phase and contrast. The feasibility of Doppler shift compensation by Raman frequency modulation is theoretically analyzed. And linear modulation and trigonometric function modulation methods are proposed to effectively restrain the Doppler effect for the accelerometers and gyroscopes, respectively.3. For cold atom interferometry gravimeter, the gravity measuring method of Raman frequency changing rate scanning in different pulse duration of T is introduced. Based on the theoretical model established in this paper, the possible measuring error is fully analyzed. Through the calculation of atomic classical trajectory and precise interference phase under the action of gravity and Earth’s rotation, it’s verified that the Coriolis force can decrease the contrast and introduce measuring error. Then the feasibility of Raman vector rotating method used to weaken the Coriolis effect is analyzed.4. For cold atom interferometry gyroscope, the absolute rotation measuring method of atomic velocity scanning is introduced. The applicability of the method in approximation model and exact model is analyzed separately. A compensation correction method is investigated when considering the Doppler effect under the precise model. With the simulation analysis, it’s shown that the method with Doppler compensation and rotation shift can realize the measurement with high-precision for absolute rotation ranging between 10-5rad/s and 3rad/s.