Research On Frequency Stabilized Technology Of He-Ne Laser With Thermoelectric Cooler

In precision measurement, wave length is the practical length standard. But frequency (wave length) stability of He-Ne laser running freely is only 10-6, which can not satisfy extra-high precision measurement. Application of laser frequency stabilized technology is to get interference laser with high wave stabilization to enhance measure precision and monitor product quantity.Frequency stabilization laser based on transverse Zeeman effect provides several characters such as high stabilization frequency, powerful anti-interference ability, great power output, low frequency of beat signal which is easy to be received and processed. It puts out linear polarized light with better coherence and polarization directly, which is advantageous for physical measuring such as polarization and birefringence. So stabilized Transverse Zeeman He-Ne laser (STZL) is applied in biologic detection, polarization character test, thin film thickness measure, reflectance and refractive ratio measure, and mini-distortion measure.The paper introduces popular frequency stabilized technology of He-Ne laser, mainly studies on Zeeman Effect frequency stabilized technology through comparing transverse and longitudinal Zeeman Effect. It also presents temperature controlling with TEC (Thermoelectric Cooler), which can both overcome temperature accumulate of heating type and low accuracy of wind cooling type by analyzing merits and drawbacks of heating and wind cooling laser frequency control. Through experiment the paper analyses temperature property of laser tube. General design scheme of frequency stabilization laser with TEC is proposed based on studies above.The frequency stabilization laser is composed of primary and subsidiary control parts. The primary part is frequency stabilized laser controlling, and the subsidiary is crust temperature controlling. The subsidiary part is to eliminate influence from circumstance. Mechanic structure, beat signal collection circuit, MCU control and DA transform output circuit, TEC drive circuit, temperature measurement circuit constitute hardware of the system. PID fuzzy control program of MCU, computer program for real-time display of beat signal and crust temperature constitute software of the system.The instrument has been designed, assembled and run. It has been tested that frequency stability of instrument developed reaches 1.74×10-9, temperature of laser tube is around 430C when frequency is stabilized, which achieves the anticipation.