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In precision measurement , the wavelength of the laser is usually used as the reference length . But the free-running helium-neon laser, optical frequency ( wavelength ) stability is only 10-6 , unable to meet the requirements of ultra- precision measurement . Laser frequency stabilization technology is to obtain high and stable wavelength coherent laser light source , thereby improving measurement accuracy , and strictly control product quality. Zeeman effect on laser frequency stabilization , high frequency stability , anti-interference ability , high output power , low frequency beat signal , easy to receive and process , can be directly output coherence and the degree of polarization is very good linearly polarized , easy to measure polarization , birefringence and other physical quantities . It can be used bioassays polarization feature detection , thickness measurement , refractive index measurement , the object so slight deformation measurement . This article describes the common helium-neon laser frequency stabilization technique , focusing on the Zeeman effect frequency stabilization technology, the longitudinal and transverse Zeeman laser characteristics were compared , analyzed the heating and cooling are two ways to control the laser cavity length the advantages and disadvantages , developed using semiconductor cooler (TEC) temperature control program , both to overcome the heated temperature heat accumulation and easy control deficiencies , but also air-cooled frequency stabilization can solve the problem of low precision , but also analyzed the laser tube experiments under different conditions temperature characteristics. In the study, based on the development of semiconductor refrigeration type helium-neon laser frequency stabilization of the overall program . Laser frequency stabilization system of the main control section from the two , the main control part controls the laser frequency stabilization , the temperature control housing from the control section to reduce the external environment of the laser frequency stabilization of the control section . System hardware section, including temperature mechanical structure, the beat frequency signal acquisition circuit , microprocessor control and D / A converter output circuit , drive circuit semiconductor refrigeration , temperature measurement circuit ; software parts , including SCM fuzzy PID frequency stabilization control portion , PC beat frequency real-time temperature curve display program with the shell . Instruments completed the design , assembly and adjustment , run tasks , and its frequency stability were measured , frequency stability index was 1.74 × 10-9, frequency stabilization of the laser tube temperature at 430C or so, to achieve the desired objectives.
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