Second-Order Vector Mode Propagation in Hollow-Core Antiresonant Fibers.

Lili Li,Limin Xiao

doi:10.3390/mi10060381

Abstract

Second-order vector modes, possessing doughnut-shaped intensity distribution with unique polarization, are widely utilized in material micromachining, optical tweezers, and high-resolution microscopy. Since the hollow-core fiber can act as a flexible and robust optical waveguide for ultra-short pulse delivery and manipulation, high-order vector modes guided in hollow-core fibers will have huge potential in many advanced applications. We firstly reveal that a second-order vector mode can be well guided in a hollow-core antiresonant fiber with the suppression of the fundamental mode and other second-order vector modes at the red side of transmission band. We interpret our observation through a phase-matched coupling mechanism between core modes and coupled cladding modes. A single second-order vector mode such as TE01, TM01, or HE21 can be guided with low confinement loss at specific wavelengths with appropriate structure parameters. Our proposed hollow-core fibers have a modal engineering function which will open up a new avenue toward the single second-order vector mode propagation and its fiberized applications.

Highlights

Hollow-core antiresonant fibers (HC-ARFs) attract considerable interest for their simple geometries and extraordinary performances [1,2,3], which are utilized for a wide range of applications such as telecommunications [4], micromachines [5], surgical procedures [6], ultraviolet laser delivery [7], mid-infrared fiber lasers [8], and optofluidic sensors [9]
We firstly demonstrate the unique modal-guiding property in a HC-ARF, where only one second-order vector mode is well guided with the suppression of the fundamental mode and other second-order vector modes at the red side of the transmission window
Since the hollow-core fibers (HCFs) are extremely important for ultra-short pulse laser delivery, our selective second-order vector mode guiding in a HC-ARF will open up advanced applications such as laser drilling [39], particle trapping [40], and microscopy [41] by using ultra-short pulse lasers

Summary

Introduction

Hollow-core antiresonant fibers (HC-ARFs) attract considerable interest for their simple geometries and extraordinary performances [1,2,3], which are utilized for a wide range of applications such as telecommunications [4], micromachines [5], surgical procedures [6], ultraviolet laser delivery [7], mid-infrared fiber lasers [8], and optofluidic sensors [9]. A new design of the solid-core PCF was proposed to suppress the fundamental mode by the coupling between the fundamental mode and the cladding mode to keep the second-order modes with low confinement loss [35]. Another theoretical work by Chen et al focused on selectively eliminating the fundamental mode or the second-order mode through the use of complex structures with a high-index core and a photonic bandgap cladding [36]. The hollow-core fibers (HCFs) have unique advantages for ultra-short pulse laser delivery over solid-core fibers, and the ability to guide only second-order vector mode in the HCFs will open up many new applications. Since the HCFs are extremely important for ultra-short pulse laser delivery, our selective second-order vector mode guiding in a HC-ARF will open up advanced applications such as laser drilling [39], particle trapping [40], and microscopy [41] by using ultra-short pulse lasers

Fiber Structures and Modal Engineering Conception

Characteristics of Second-Order Modes in HC-ARFs and Discussion

Conclusions