Study On Laser Beam Quality Detection Method Using Computational Holography (CGH)

Beam quality is an important characterization of laser parameters. Its quality directly affect the performance of the optical system. Effective measurement technology is the basic security of quality improvement. Therefore, the study of laser beam quality measurement has increasingly become a hot topic. High precision and real time measurement is a big difficulty in this research field.This Paper first studies the evaluation of various parameters of laser beam quality and their method of measurement. In order to achieve the beam quality with high precision and real-time measurement, this paper selects mode decomposition based on computer generated holography as the research object and explores the technology to acquire the laser mode information. For Hermite-Gaussian beam as an example,this paper studies the complex amplitude transmission function to achieve mode decomposition from the laser mode theory. Coding algorithm of transforming the complex amplitude modulation to a pure phase modulation is researched.Then this paper studies how to calculate beam quality factor from the energy distribution in the far field.This paper verifies the theoretical feasibility of the measuring method through the far-field diffractive numerical simulation and optical software (Virtuallab) simulation respectively. Phased-only spatial light modulator is used as a Computer-generated holography to construct experimental verification optical system.Then this paper gauges the beam quality of He-Ne laser with the optical system and the measuring results are compared to traditional method. Comparative results reflect the method has high precision and real-time performance.