Tunable Narrow-Linewidth Ring Laser Based on the Polarization Conversion in a Tapered Fiber-Coupled Whispering Gallery Mode Resonator

Abstract

Based on the polarization conversion in a tapered fiber-coupled whispering gallery mode (WGM) system, a simple-structured narrow linewidth band-pass filter was fabricated and a narrow linewidth ring laser was demonstrated. With a fiber Bragg grating (FBG) to further select the resonant mode, the ring laser could be in the single-longitudinal-mode with the linewidth about 6 kHz and its wavelength could be tuned from 1540.10 nm to 1570.01 nm. Benefit from the dense modes in the WGM resonator, high conversion efficiency, and better stability of the structure, a tunable dual-wavelength laser could be achieved based on two FBGs with different resonant wavelengths. The configuration of the proposed laser is simple and stable, which will benefit its applications in the future.

High-Performance Fiber Ring Laser Based on Polarization Space Parity-Time Symmetry Breaking

“…Consequently, by directly using conventional optical filters as wavelength selection elements for laser oscillators, it is challenging to achieve single-mode outputs. To overcome this challenge, common techniques for single-mode selection in fiber ring lasers include compound rings with Vernier effects [1][2][3][4][5], saturable absorbers [6][7][8][9], cascaded microfiber knots [10], whispering gallery mode resonator [11], phase-shifted fiber Bragg gratings [12], and dynamic gratings [13,14] to establish narrow linewidth filters. However, these methods often require complex cavity structures and fine parameter tuning.…”