Research And Application Of Wavelength Correction And Stabilization Of Laser Diode

Nano-positioning stage plays an important role in the field of nano-metrology.In recent years,with the development of nano-metrology,new requirements have been put forward for the positioning accuracy and volume of the nano-positioning stage.Laser interferometer has the advantages of high precision and high speed,which can be used as the displacement feedback device of the nano-positioning stage.In order to meet the development requirements of the nano-positioning stage,the laser interferometer needs to reduce the volume while ensuring the measurement accuracy.So that it can be integrated into the nano-positioning stage to achieve real-time displacement measurement and feedback.Laser diode has the advantages of small volume,low cost and easy integration.It can replace He-Ne laser as the laser source of the laser interferometer to reduce its volume and cost.In the measurement method based on the principle of the laser interference,the laser wavelength is the measurement basis,which determines the accuracy of the measurement method.However,the wavelength accuracy and stability of laser diode are low,which limits the measurement accuracy of the laser interferometry with laser diode as its laser sources.Therefore,it is essential to real-time correct and stabilize the wavelength of the laser diode in real time is of great significance for improving the measurement accuracy of the laser diode interferometer.In this paper,a real-time wavelength correction method based on grating diffraction principle and the laser autocollimation principle and a real-time wavelength stabilization method based on the automatic stable temperature control and the automatic beam drift compensation method are proposed.A wavelength correction system and a wavelength stabilization system for laser diode are developed.The system has the characteristics of simple-configuration,low-cost and small-size,and can be integrated into a small laser diode interferometer to achieve real-time wavelength correction and stabilization.Compared with the traditional wavelength measurement method based on the laser diffraction principle,the proposed method not only considers the influence of the change of the laser diffraction angle on the laser wavelength,but also considers the influence of the change of the laser incidence angle and the pitch change of the diffraction grating caused by temperature on the laser wavelength.The measurement accuracy of the laser wavelength has been improved from0.01 nm to 0.006 nm.In addition,the laser beam drift compensation system based on PID control principle is added to the traditional automatic temperature stabilization system.In this beam drift compensation system,a high-precision two-dimensional angle adjustment module driven by PZT is developed.According to the measured beam drift and the PID control principle,the angle of the precise two-dimensional angle adjustment module is changed to change the laser beam direction,from which the influence of laser beam drift on wavelength stability is reduced.The wavelength stability of the laser diode has been increased from 10^-4to 10^-6.At the same time,the measurement software of wavelength correction and stabilization system is compiled by the LabVIEW,which can realizes collecting,processing and saving of the measurement data.Finally,the real-time laser wavelength correction and stabilization system is integrated into the small laser diode interferometer developed by the research group to further verify the feasibilities of the wavelength correction and stabilization systems.Compared with a commercial laser interferometer,the measurement accuracy of small laser diode interferometer integrated with wavelength real-time correction and stabilization systems is improved from 0.6μm to 0.2μm.