Coupling constant of triple-clad long-period fiber grating

• Published in: Optoelectronics letters 2006-01, Vol.2 (1), p.27-30
• Main Authors: Gu, Zheng-tian, Xu, Yan-ping, Chen, Jia-bi
• Format: Article
• Language: English
• ISSN: 1673-1905; 1993-5013
• DOI: 10.1007/BF03033586

TN253%TP212.14; Based on the method of vector-field analysis,the relationship between the core-mode/cladding-mode coupling constant kcl-co1v-11 and mode order v is studied.It could be seen that the coupling constants of the l=1 low-order HE cladding modes are larger than that of the l=1 low-order EH cladding modes when v≤41.For cladding modes with v＞41,the coupling constants of the l=1 low-order HE and EH modes are comparable to each other.The plotted local intensity curves of the six lowest-order(l=1) cladding modes show that the low-order HE modes have a larger proportion of intensity located in the core than the low-order EH modes.Further,the relationship between the coupling constant kcl-co1v-11 and the film refractive index as well as the film thickness is studied.The results indicate that the coupling constant changes monotonously with the film refractive index changing.As the film thickness increases,the coupling constant decreases slowly with irregularly changes in a certain region of the film thickness,which matches the experimental results of Nicholas D.R.