| Dual-frequency laser with tunable frequency-difference has been found wide applications in the fields of laser interferometry,optical sensing and terahertz generation.When a dual-frequency laser is used as light source of an absolute-distance interferometric system,in order to improve accuracy of the measured distance,it requires that the frequency difference of dual-frequency laser should be tuned and be as large as possible.Compared with the traditional dual-frequency laser,the two-cavity dual-frequency solid laser has a number of advantages such as all-solid state,simple structure,small volume and wide frequency tuning range.Therefore,it is of great significance to research the techniques of frequency-difference tuning of two-cavity dual-frequency solid laser.The main contents of this dissertation are as follows:First of all,the domestic and overseas research status and development trend of frequency-difference tuning techniques of dual-frequency lasers have been briefly described.The working principle,system composition and working characteristics of the LD pumped two-cavity dual-frequency Nd:YAG laser have been described in detail.Secondly,Aimed at birefringent filter two-cavity dual-frequency Nd:YAG laser,two kinds of frequency-difference tuning schemes have been respectively designed,being named as crystal-axis-tilted frequency-difference tuning and dual-quarter-wave plates frequency-difference tuning.The corresponding feasibilities of the two frequency-difference tuning schemes have been theoretically analyzed.Thirdly,the experimental system of tunable frequency Nd:YAG laser with tilted crystal axis and of double quarter-wave plates tunable frequency Nd:YAG laser system have been established.The oscillation characteristics and frequency tuning characteristics of the two laser systems have been studied experimentally.The results show that the laser frequency can be tuned by changing the tilt angle of birefringent crystal axis from-5° to 5°,and the amount of frequency tuning is 150GHz.With the tilted angle of the crystal axis increased,the laser frequency and the output power changed periodically.The laser frequency can be tuned by changing the included angle between the fast axis of the double quarter-wave plates from 0° to 360°,and the amount of frequency tuning is 146.4GHz.With the included angle between the fast axis increased,the laser frequency changed periodically.Fourthly,the experimental system of two-cavity dual-frequency Nd:YAG laser has been established,and the characteristics such as oscillation,frequency-difference tuning and laser polarization of the system have been investigated experimentally.The results show that the linear cavity and the rectangular cavity simultaneously oscillated in a single longitudinal mode.The output dual-frequency laser at 1064nm is orthogonally and linearly polarized.The frequency difference of the system can be tuned by regulating the tilt angle of crystal optical axis in the linear cavity from 1.6°?3.4°,and the tuning range is from 5.217 GHz to 147.36 GHz.The maximum frequency-difference obtained is up to 147.36GHz,which has approximately reached to the fluorescence line width of Nd:YAG crystal.In summary,the frequency-difference tuning method and technology of two-cavity dual-frequency Nd:YAG laser have been investigated theoretically and experimentally in this paper.The crystal-axis-tilted frequency-difference tuning scheme and dual-quarter-wave plates frequency-difference tuning scheme have been designed.Among them,the crystal-axis-tilted frequency-difference tuning scheme has simple structure,wide tuning range and good practicability. |
PDF Full Text Request