XUE Linlin,Bras Samuel Malumba Timoteo,QIU Weiwei,WANGZhongpeng.Ultra-broadband optical filter based on chirped long-period fiber grating using leaky mode coupling[J].Optoelectronics Letters,2022,(10):577-582 Ultra-broadband optical filter based on chirped long-period fiber grating using leaky mode coupling Author Name Affiliation XUE Linlin  School of Information and Electronic Engineering, Zhejiang University of Science and Technology, Hangzhou 310023, China  Bras Samuel Malumba Timoteo  School of Information and Electronic Engineering, Zhejiang University of Science and Technology, Hangzhou 310023, China  QIU Weiwei  School of Information and Electronic Engineering, Zhejiang University of Science and Technology, Hangzhou 310023, China  WANGZhongpeng  School of Information and Electronic Engineering, Zhejiang University of Science and Technology, Hangzhou 310023, China  Abstract:       An ultra-broadband optical filter was proposed and demonstrated based on leaky mode coupling in a coated chirped long-period fiber grating (CLPFG). The CLPFG was coated with a material whose refractive index (RI) was higher than that of the fiber cladding, enabling the coupling of the core mode to leaky modes, to achieve a desired coupling efficiency. Complex coupled-mode theory was used to investigate the power evolution of the core mode that resulted from the coupling. From this, the conditions in which the core mode power attenuates the most rapidly were identified. In addition, phase matching turning point (PMTP) was used in the design, to overcome the conflict between the range of grating period change and the grating length in the CLPFG. Finally, an optimized CLPFG-based filter with a length of 3.5 cm was obtained, which has a symmetrical attenuation band with an operating bandwidth over 300 nm. Within the operating bandwidth, the flatness is less than 2.5 dB and the transmittance is lower than 0.1%. Hits: 393 Download times: 0 View Full Text    Download reader