Design of a mid-infrared single-mode laser based on parity-time symmetry breaking in air-clad hollow-core ZBLAN fiber micro-resonator

Abstract

In this paper, we propose a single-mode laser operating in the mid-infrared regime by exploiting parity-time (PT) breaking in a whispering gallery mode (WGM) micro-resonator based on air-clad hollow-core ZBLAN fibers. By introducing alternate gain–loss modulation regions with refractive indices respectively having the same real parts but opposite imaginary parts into the air hole clad region of the hollow-core fiber infiltrated with optical functional materials, a PT symmetry system could be set up and specific WGM in PT-broken state whose electric field distribution matches the gain–loss modulation pattern can be excited to realize single-mode laser emission around 5 μm. And moreover, simulation results indicate that high precision laser wavelength tuning with a sensitivity of 1.623 nm RIU−1 can be achieved by adjusting the refractive index of the functional materials filled into the cladding air holes.