Method for measuring cladding light proportion of double-clad fiber laser

Abstract

The invention discloses a method for measuring a cladding light proportion of a double-clad fiber laser. The method comprises: performing equal-ratio amplification imaging on the end face of the output fiber of the double-clad fiber laser by using a lens group; disposing a diaphragm with an adjustable aperture diameter on the image surface of the lens group; enabling the fiber core light in the output light of the double-clad fiber laser to pass through the diaphragm but enabling the cladding light in the output light of the double-clad fiber laser to be blocked by the diaphragm by adjusting the aperture diameter of the diaphragm; testing the power P1 of output light spot in front of the diaphragm and the power P2 of fiber core light spot behind the diaphragm to obtain the proportion of the cladding light of the output light of the double-clad fiber laser as (P1-P2) / P1. The method is large in measurement range, high in measurement precision, and can be used for measuring the cladding light proportion of a high-power double-clad fiber laser.

Description

technical field [0001] The invention belongs to the field of fiber lasers, and relates to a method for measuring the cladding light ratio of a double-clad fiber laser, in particular to a measuring method for testing the cladding light ratio of a high-power fiber laser. Background technique [0002] Fiber lasers have obvious advantages in beam quality, volume, weight, efficiency, heat dissipation, etc., and have become one of the most popular research directions in the field of lasers. Single-clad gain fibers were often used in early fiber lasers. The characteristic of this fiber is that both the pump light and the signal light are transmitted in the fiber core. Since the diameter and numerical aperture of the fiber core are small, this makes the pump injected into the gain fiber The total power of the pump light is limited, which restricts the power increase of the fiber laser. The structure of the double-clad gain fiber includes a core, an inner cladding and an outer cladd...

AI Technical Summary

Problems solved by technology

At this time, the response of the detector to the cladding light field will be equivalent to the noise of the detector itself, which means that the detector cannot detect the cladding light field and the outer boundary of the cladding light field, that is, it cannot simultaneously detect the cladding light field and the fiber core light field imaging

On the other hand, since the core and the inner cladding of the double-clad fiber differ greatly in numerical aperture and cross-sectional area, it is impossible for the lens group to form a clear image of the core and the inner cladding at the same position (the aberration is less than 0.5 times the wavelength), that is, for the image of the core and the image of the inner cladding, there must be a blurred edge, which will lead to a decrease in the accuracy of the results of the detector test

Therefore although the patent document CN103616165A can realize the separation of the cladding light field and the fiber core light field under certain conditions, it can be used to test the loss of the optical fiber (core loss and inner cladding loss), but the measurement range of this method is severely limited Due to the dynamic response range of the detector and the accuracy is not ideal, it is not suitable for testing the cladding light ratio of the output light of high-power fiber lasers

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