Excitation of high-quality orbital angular momentum vortex beams in an adiabatically helical-twisted single-mode fiber

Abstract

A novel method to control the parameters of a chiral fiber grating structure is proposed. Mode couplings are controlled in real time during the twisting fabrication process. This chiral grating structure can satisfy the phase-matching condition for generating high-quality orbital angular momentum (OAM) beams, with an order mode of conversion efficiency over 99.9%. Both theoretical analysis and experimental results of this OAM mode conversion have been investigated, with good agreement. The results demonstrate a dual-OAM beam converter with a charge of ±1 for the right- and left-handed CLPGs, respectively. The high-quality OAM beam generated in this twisted single-mode fiber process may find excellent applications in optical communications.

High linear sensitivity humidity and temperature sensing based on chiral long-period fiber grating

“…1, the CLPG is fabricated by twisting a single-mode fiber (SMF) (Corning, SMF-28e(R)). The fabrication setup consists of three parts: the double-beam CO2 laser heating part, the twisting part, and the online monitoring part 38 . Experimentally, a two-beam CO2 laser is used to heat and soften the fiber due to the advantages of clean, uniform heating, and power stability.…”

“…The fabrication setup consists of three parts: the double-beam CO 2 laser heating part, the twisting part, and the online monitoring part. 38 Experimentally, a two-beam CO 2 laser is used to heat and soften the fiber due to the advantages of clean, uniform heating, and power stability. As a result, the resulting fiber gratings have very flat surfaces and lower fiber gratings losses.…”

“…[25][26][27][28][29] Benefiting from its periodic twisted structure based on physical deformation, the CLPG is more stable, non-degradation, more flexible preparation, and more sensitive to changes in surrounding environments, which has significant applications in OAM converters, all-fiber circular polarizers, and special sensors (especially high temperature or harsh environments). [30][31][32][33][34][35][36][37][38] In this study, a humidity/temperature sensor with high sensing linearity and stability was designed and fabricated by wrapping the PVA/graphene nanofiber film on CLPG. The humidity sensitivity of the sensor is −9.92 pm∕%RH, exhibiting a high linearity of 0.995.…”

“… – 29 Benefiting from its periodic twisted structure based on physical deformation, the CLPG is more stable, non-degradation, more flexible preparation, and more sensitive to changes in surrounding environments, which has significant applications in OAM converters, all-fiber circular polarizers, and special sensors (especially high temperature or harsh environments) 30 – 38 …”

The study of broadband circular polarizer based on double-helix chiral fiber long period grating

“…However, according to the mode coupling theory of CLPG, the effective bandwidth of circularly polarized light generated based on double helix CLPG is only ~10 nm, which greatly limits its application in alloptical communication and sensing systems. In our previous study, we found that the principle of double resonance based on the inflexion of mode dispersion can increase the bandwidth of mode coupling and realize the filtering characteristics of ultra-broadband [5]. Therefore, introducing the dispersion transition characteristic into the double-helix CLPG mode coupling, it is expected to realize the broadband all-fiber circular polarizer.…”