Abstract In this paper, a new method to generate dark hollow beam (DHB) was introduced. The method is based on a special fiber with three-layer step-index structure and the technique… Click to show full abstract
Abstract In this paper, a new method to generate dark hollow beam (DHB) was introduced. The method is based on a special fiber with three-layer step-index structure and the technique of long period fiber grating (LPFG). The working wavelength depends on the parameters of the special fiber. The wavelength of 532 nm was applied in the application described in this article. High quality DHBs were generated in the experiments. Several experimental results have been shown to demonstrate the influences of grating pitch of LPFG. Methods to improve the quality of DHB were discussed.
               
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