Research On Beam Quality Measurement Technology By Quadriwave Shear Interference

The quality of output beam has always been the focus of laser research and development,design,production and application,so accurate measurement of the laser beam quality is particularly important.At present,the most commonly used measurement method for laser beam quality is the multi-point method.This measurement method has a long measurement period and is easy to introduce errors.It can not monitor the beam quality in real time,especially for the measurement of pulsed laser beam quality.To solve the problem of traditional beam quality measurement methods.this paper proposes a beam quality measurement method based on quadriwave lateral shear interference technology,which uses the wavefront information of the laser beam to deduce the quality of the laser beam,and only one sample is required to obtain performance parameters of the laser beam.This paper starts from the basic theory of transverse shear interference,simulates and discusses the differences between two-wave,three-wave and four-wave interferograms.Construct a quadriwave lateral shear interference system,and perform image preprocessing such as Fourier transform on the interferogram to obtain the differential wavefront phases in two orthogonal directions(X and Y directions),using differential Zernike polynomials.The wavefront phase is reconstructed,and then the laser complex amplitude is reconstructed.The angular spectrum method is used for diffraction transmission to obtain beam widths at different positions to fit the transmission characteristic curve of the laser beam in space and obtain the beam quality of the laser beam.Using the He-Ne laser as the tested laser source,a quadriwave lateral shear interference beam quality measurement device with a checkerboard phase grating as a beam splitting device and an area array CCD camera as an image sensor was built.The transmission characteristic curve in space of the He-Ne laser is reconstructed and the beam quality is measured.Through comparative analysis with the measurement results of the M~2-200 beam quality measuring instrument and the SID-4 wavefront sensor,the relative error between this measuring device and the above two beam quality measuring instruments does not exceed 5%.