Studv Of Optical Phase Lock Loop Based On Analog PID

We can obtain cold atoms by using lasers to cool and trap them. Cold atoms can be applied to developing cold atom interferometry. Till now, cold atom interferometry has been widely used in precise measurement, such as atom clock, atom gravimeter, atom gyroscope, et al. In the experiments of cold atom interferometry, one of the key techniques is to lock the phase of two semi-conductor lasers, which are used as Raman beams.The Optical Phase Lock Loop (OPLL), which is based on analog PID, is presented in this thesis. We use the technique of OPLL to achieve the goal of precisely locking the phase of two Raman lasers. The frequency difference between two Raman lasers is6.834GHz, equal to that of87Rb’s two ground states. One of the Raman beams is frequency locked to a spectral line of87Rb. Firstly we use a high-speed photon diode to attain the beat signal between the two Raman lasers. Secondly, mix the beat signal with a7GHz signal to get a signal of165MHz. Thirdly, divide the165MHz signal and then mix it with a standard signal of82.5MHz to do the phase detection. Finally, the error signal of output is sent to the unlocked Raman laser after feedback. In the phase control system of semi-conductor lasers, we focus on studying the analog PID and the phase detector, analyzing their effects on phase noise, and further, analyzing these effects on precise measurement of the atom interferometry. The details of the each chapter are shown in the following.The study background of cold atom and the cold atom interferometry are introduced in Chapter1. Then present OPLL, the key techniques of cold atom interferometry experiments, together with its development and applications. At last, we also present the purpose and significance of this thesis.The principle of cold atom interferometry is presented in Chapter2. Firstly, we analyze the interaction between lasers and atoms. Then we present the cold atom interferometry based on the Raman transitions. Finally we analyze the effects of the phase lock noise on the interference fringes. And in Chapter3, we mainly present the semi-conductor lasers, which are used to produce the Raman beams. At first, we introduce the development of lasers. And then we present the semiconductor laser and its operating principle.The principles of phase locking Raman lasers are stated in Chapter4. Firstly we introduce the PLL principle of lasers. Then we analyze the principle of OPLL.The research of OPLL in our experiment is discussed in Chapter5. At first, we introduce the phase detector, and the analog PID. Then we analyze the process of the phase locking for semi-conductor lasers. At last, we focus on the result of the phase noise and analyze its effect on the atom interferometer.Finally, we get the conclusion and outlook in Chapter6, summarizing the experiments and expecting to obtain better results in the phase locking.