Analysis of laser M2 determination in a quadriwave lateral shearing interferometer with CCD vertical blooming

Abstract

Abstract Charge-coupled device (CCD) vertical blooming is inevitable in silicon-based cameras when near-infrared lasers are measured. In this study, we analyze the mechanism responsible for the influence of CCD vertical blooming on the beam quality factor (M2) measurement with a quadriwave lateral shearing interferometer (QWLSI). Based on a CCD vertical blooming model, we reconstruct the bloomed interferogram, which is used to retrieve the intensity and phase distributions of the laser. Then, the relationship between the M2 and degree of CCD vertical blooming is revealed. In addition, the M2 of single- and multi-mode lasers is measured with the QWLSI under different degrees of vertical blooming streaks. The results from the experiment are reasonably consistent with the simulation results. Meanwhile, the method of improving the exposure time of CCD camera for suppressing the blooming is also analyzed, indicating that the method can effectively suppress the influence of the blooming on the M2 measurement in a QWLSI.