A Measurement System Of 633nm Laser Frequency Stability

Owe to its merits of simple structure, high wavelength stability and visible measurement optical path, laser heterodyne interferometer constructed by 633nm stabilized laser is widely applied in many fields, such as nanometer technology, precision machinery, microelectronics and so on. As the development of ultra-precision machining and measurement, it badly needs an improvement of the laser wavelength stability. Accordingly laser frequency stabilization technology becomes a hot-spot of ultra-precision machining and measurement.Frequency stability is an important character of Laser; however, it is impossible to measure the laser stability directly because of its ultra-high frequency. Usually indirect physical quantity is used to denote the laser stability, but the accuracy is rather finite, on the other hand, laser stability measurement device by reference method is very expensive, due to the high cost of the I2 stabilized reference laser, which is not suitable for a common laboratory.In this paper a simple 633nm laser frequency measurement system has been developed with HP5518A instead of I2 stabilized reference laser, which provides a powerful tool for the study of stabilized laser. This paper has finished a series of works as following:1. Make quantified analysis of the reference laser effect to the measurement of the measured laser frequency stability.2. Design high space collimation heterodyne beam path, high performance signal processing unit and frequency measurement unit, constitute a complete test system of laser frequency stability.3. Finished visible data-processing program so that the test system is very friendly to the users.4. Discuss the relationship of the noise and the frequency stability with different sample time.5. Qualitatively analyze the contribution of the refractive index fluctuation to the laser frequency stability measurement, present resolution to reduce the adverse effect.The measurement results of a same stabilized laser by this system are close to that of National Institute of Metrology P. R. China, strongly suggest that our system is correct in design principle and the measured results are believable.