Research On Water-cooling Technology For Frequency Offset Locking Frequency Stabilized Laser

Owing to the rapid development of science and technology, the super precision machining attracts more attention. As a result, the ultra-precision measurement technology is required to be better. The laser interferometer is the most important technology in super precision displacement measurement and positioning. As the light source of the laser interferometer, the frequency stabilized laser provides the wavelength standard for the interferometer. The stability of the wavelength will affect the accuracy of the interferometer. The traditional thermal stabilized He-Ne laser, with lower frequency stability, releases thermal pollution to the environment. The thermal pollution will decrease the interferometer’s measuring and positioning accuracy. This problem has become one of bottlenecks limiting the development of new generation of the dual-frequency laser interferometer.This paper, titled “Research on water cooling technology for the frequency offset locking thermally stabilized He-Ne laser”, analyzes the natural cooling properties of the traditional thermally frequency stabilized laser and studies the relation between cooling properties and measurement precision of the laser interferometer. Based on studies above, this paper applies the active water-cooling technology and designs some kinds of water-cooling structure. Through simulating the operating characteristics of the water-cooling process, the structure of water-cooled pipe is optimized. And the application effect is verified through the following test. The main contents are as follows:Firstly, this paper proposes the enhanced water cooling system. It analyses the traditional thermally frequency stabilized laser’s heat dissipation and the water cooling technology. Taken into account the analysis, the paper points out a feasible water cooling solution Thermostatic water bath can keep the temperature of the water constant by its own independent temperature control system. Two temperature sensors are installed in the inlet and outlet of the water cooling stabilized laser, in order to measure the temperature of the water flow and calculate the instantaneous temperature difference. The water pump can control the flux of the water. The water flow into the inlet and out of the outlet, then pass through flow meter, water pump, throttle and get back to the water bath. All these components form a water circulatory system, in order to provide a stable thermal environment for the laser tube.The paper simulates and optimizes the water cooling structure, which is the core part of the water cooling system. The radiating effect and uniformity of temperature field of the structure is the decisive factor of the stability of the laser tube’s ambient temperature. The stability will affect the laser’s frequency stability. As a result, various water cooling structure models are designed in this paper. Through simulation analysis, the structure with the best radiating effect and uniformity of temperature field is adopted. Furthermore, the optimal flow velocity is gotten by analyzing the relationship between flow velocity and radiating effect, uniformity of temperature field.The paper analyses the control system of the water cooling offset frequency locking laser. Based on the analysis of the control system of the traditional thermally frequency stabilized laser, the laser tube,under the water cooling thermal environment, is set as the controlled plant. The thin-film heater is actuator, which is wrapped around the laser tube to thermally adjust the laser cavity length. Taken in to account effect of the water cooling system, the paper proposes a new control system to increase the laser’s frequency stability.The paper designs a water cooling offset frequency locking frequency stabilized laser. The laser largely combines the He-Ne laser tube, water cooling structure, electrical circuit of optical beat center frequency measurement, dynamic digital control system. The laser mechanical structure is compact and easy to adjust, in order to guarantee the laser’s frequency stability.Finally, the paper proposed the water cooling offset frequency locking frequency stabilized laser, whose frequency stability is less than 104.2 10-± ′.