Design Of Digital Auxiliary Lock System For The Semiconductor Laser

As is known to all, semiconductor laser plays a very important role in the atomicmagnetometer. In accordance with the working principle of the atomic magnetometer,the laser frequency is needed to lock in cesium atomic hyperfine resonance line anddemanded a very high stability at the frequency of the laser. The semiconductor laserlocks its frequency in cesium atom hyperfine resonance line by saturable absorptionspectrum to achieve the purpose of frequency stabilization in traditional solutions.However, the semiconductor laser may lost the frequency of cesium atomic hyperfineresonance line due to a variety of reasons with time going by. As a result, this subjectis asked to design a digital auxiliary locking techniques that can continuously adjustthe output according to the working state of the locked close-loop. This design makesthe system basically working in the locked condition, which effectively increases thestability at the frequency of the laser. The laser will be locked in the stable state forlong-term generally.The following work was made in this paper:Firstly, we can see the details about the background of the subject, andexpounded the meaning and methods of the semiconductor laser frequencystabilization. We discuss polarization spectroscopy and dichroic atomic vapor laserlock (DAVLL) in theory, The advantages and disadvantage of the techniques areanalyzed. Then research objectives is proposed.Secondly, the general scheme of the system is designed and analyzed from bothparts of hardware and software. In order to achieve the system goals, we use amicrocontroller unit as the master core component of system, because its fast speed,low price, expand more purposes easily in the future. C is chosen to be used becauseit’s simple and easily understood.Thirdly, the discussion of hardware is divided into several parts: input channels,the control module, the digital-to-analog converter, the sample and hold circuit, serialport communication and the power circuit. We discussed the principle and detaileddesign of these parts. The EMC design is also involved.Its working principle is to taketurns monitoring the input signal of each path, the MCU will react after it judge whether the input sigal is positive voltage or negative voltage. Microcontrolleradjust the output and deliver it into digital-to-analog conversion dice.The analogsignal will be locked its value by the sample and hold circuit and waiting for the nextchange. We divide the program into several parts according to their different purpose.We also take some measures for the software anti-jamming.Finally, the related functional experiments are made on the system, and theexperiment results meet the desired requirements.However, due to my limited abilityand time, the digital auxiliary lock system for the semiconductor laser in this paperstill have greater development room for improvement. If we can replace tantalumcapacitors which have better time constant characteristics, I believe the systemperformance can be further improved. In addition, the speed of chips in the circuitalso has a big room for improvement, if we can select chips which have higher speedand better performance, the circuit will run faster and make a significant reduction inthe output drift. Because the system is still set aside a large number of interfaces, sothe system can be easily and widely used as a control system. Software program usethe modular design, so it can be easily to adapt, you can even change the range, thestep length and their logical relationships.As is mentioned above, we design and produce this digital auxiliary lock systemfor the semiconductor laser. This design makes the system basically working in thelocked condition, which effectively increases the stability at the frequency of the laser.The laser will be locked in the stable state for long-term generally.