Fiber laser beam quality measurement method base on photoelectric detector and CCD camera

Abstract

The invention relates to a fiber laser beam quality measurement method base on a photoelectric detector and a CCD camera. The method comprises: an optical axis of a measured light beam is adjusted to be in a horizontal state, and a beam splitter is arranged at an optical path and thus the measured light beam is divided into two parts that are used for measuring a near field and a far field of the light beam. On the basis of measurement of the near field and the far field of the measured light beam as well as a related data analysis, a near field width and a far field width of the light beam are calculated, so that light beam quality M <2> x and light beam quality M <2>y at a corresponding direction are obtained by calculation. An M<2> factor expression based on near field and far field light intensity distribution of a beam is deduced in theory, so that a defect that the existing M<2> factor measuring instrument can not evaluate the large-size fiber laser beam quality easily can be overcome. The provided fiber laser beam quality measurement method is suitable for fiber laser beam quality measurement including a few of high order modes and some cut fiber laser beam quality measurement.

Description

technical field [0001] The invention relates to a method for measuring optical fiber laser beam quality, in particular to a method for measuring optical fiber laser beam quality based on a photodetector and a CCD camera. Background technique [0002] Beam quality is a very important indicator in the practical application of lasers, and it is generally considered to evaluate the characteristics of laser beams from a qualitative aspect. At present, there are many methods for evaluating the quality of laser beams, such as M 2 factor, beta factor, Strehl ratio, etc. [Feng Guoying, Zhou Shouhuan, "Discussion on Comprehensive Evaluation of Laser Beam Quality", China Laser, 36, 1643-1653 (2009)]. In the 1990s, A.E. Siegman proposed using M 2 factor to evaluate beam quality. M 2 The factor is defined as the ratio of the product of the beam waist width of the actual beam and its far-field divergence angle to the corresponding product of the ideal beam. It is also the most widely ...

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Problems solved by technology

The three-point method and the two-point method are more convenient to measure, but the accuracy is not high; the hyperbola fitting method performs hyperbola fitting by measuring multiple points (usually the far field and the near field should measure at least 5 effective points each), so the accuracy Higher, but the implementation is complicated, usually with the help of related precision instruments

But the M 2 Due to the limited resolution of the CCD and the fixed focal length of the conversion lens, the factor measuring instrument is severely limited in its scope of application. For the measurement of fundamental mode Gaussian beams, it can only be used to accurately measure beams with a beam waist width less than 5mm [" m 2 -200 / 200s-FWUsersGuide”, 2009, Ophir-Spiricon Inc. Document No: 11382]

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