In‐Fiber Switchable Polarization Filter Based on Liquid Crystal Filled Hollow‐Filament Bragg Gratings

Abstract

Femtosecond laser filaments are formed by surface aberration to open nano‐hole arrays, passing through the silica cladding and guiding core cross‐section of a standard telecommunication fiber. The hollow filament grating presents a strong capillarity effect to draw nematic liquid crystal (NLC) into homogeneous alignment with the cylindrical walls and presents a high birefringent response in the second‐order Bragg stopband. The NLC provides a strong extinction ratio of up to 20 dB over a ≈5 nm band with only a moderate insertion loss of <1 dB arising between the two polarization states of the shifted stopbands. The Bragg grating follows the thermo‐optic response of the NLC to further offer dynamic tuning and switching of the polarization extinction response without an increase in the insertion loss. The flexible laser writing enables tailoring of the Bragg spectral and polarization responses in the telecommunication C‐band.

Laser nano-filament explosion for enabling open-grating sensing in optical fibre

“…The nanohole array presents a responsive optical fibre sensor, retaining cladding strength while readily wetting with numerous solvents that can reach into the open photonic structure formed along with the fibre core. The nanoholes are amenable to hosting a wide range of materials, for example, such as nematic liquid crystals (NLC) 53 . The small, 200 nm diameter capillaries were found to impose a strong axial molecular alignment of NLC, manifesting in strong optical birefringence in the fibre polarisation modes that facilitated an all-fibre dynamically switchable polarisation filter 53 .…”

Integrated optical polarizers employing 2D materials

“…Fiber devices are highly effective in applications like sensing and optical communications, where maintaining the integrity of the polarized light over long distances is crucial. Conventional fiber optical polarizers achieve the selection of light polarization states by incorporating birefringent crystals or metals that show polarization-selective coupling with the evanescent fiber optical field [91][92][93]. Due to inherent limitations of these materials (e.g., polarization mode dispersion and high insertion loss [94]) and structural constraints in fiber optical polarizers, these devices face challenges in terms of fabrication, bandwidth, and tunability.…”

Quantum mechanical studies of p-azoxyanisole and identification of its electro-optic activity

“…In the reported work, a few nonlinear optical properties such as mean polarizability, anisotropy in polarizability, first-order hyperpolarizability, molar refractivity and dielectric constant were calculated, as given in Table 2. Nonlinear optical properties play an important role in electro-optic devices, 33 optical and photonic applications, 34 optical modulation, 35 optical switching, [36][37][38] telecommunications, 39 signal processing 40 and optical interconnections. 41 Usually, the organic molecules have a delocalized pi-electron system due to which these molecules show high nonlinear properties.…”