Wavelength-switchable erbium-doped fiber laser incorporating fiber Bragg grating array fabricated by infrared femtosecond laser inscription

Abstract

Wavelength-switchable fiber laser systems have many potential applications. Herein, the use of an erbium-doped fiber laser based on parallel fiber Bragg gratings (FBGs) (ASE: amplified spontaneous emission; BRM: broadband reflection mirror; CCD: charged-coupled device; EDFL: erbium-doped fiber laser; FBG: fiber Bragg gratings; IR: infrared; MZI: Mach–Zehnder interferometer; OSA: optical spectrum analyzer; OC: output coupler; PC: polarization controller; SNR: signal-to-noise ratios; 3D: three-dimensional; wavelength division multiplexing (WDM)) is proposed to achieve C + L band triple-wavelength-switchable laser output at approximately 1.5 μm. In the proposed system configuration, three parallel FBGs with different resonant wavelengths were fabricated using an 800 nm femtosecond pulsed laser. The proposed fiber laser incorporates first-order FBGs with the periods of 538, 542, and 547 nm. The femtosecond laser was propagated through polyimide coating and cladding and was focused onto the fiber core by a 63× oil lens, while FBGs were inscribed with the use of a point-by-point method to generate resonant wavelengths at 1555.3, 1569.2, and 1583.1 nm. When the FBGs were used as wavelength selectors, a lasing threshold of 85 mW was obtained, and switchable lasing with stable single- and dual-wavelength outputs was achieved based on the adjustment of a polarization controller. Concerning the switchable single-wavelength lasing, the signal-to-noise ratio was greater than 37.23 dB, and the 3 dB linewidth was less than 0.09 nm. The respective power fluctuation measurements were less than 0.22 and 0.68 dB for the single- and dual-wavelength lasers at 26 °C over a scan time of 30 min.