Abstract
A compact random fiber laser based on a short artificial Rayleigh reflector and heavily-doped Er fibers (custom-made and commercial as a reference) has been proposed, characterized and optimized in terms of efficiency, linewidth and noise level. A 10-cm artificial Rayleigh reflector with mean scattering level of +41.3 dB/mm relative to the natural Rayleigh scattering of the host fiber and low insertion loss level (∼0.05 dB/cm at 1535 nm) was fabricated using a femtosecond direct writing technique. Its implementation as a distributed output mirror in a half-open cavity of a 980-nm diode pumped Er-doped fiber laser results in random lasing at 1535 nm in single- and few-mode regimes with power up to 100 mW, slope efficiency up to 16.5%, and signal-to-noise ratio up to 60 dB. A single-frequency regime with ∼10 KHz linewidth was observed at output power up to 2.5 mW. Tunability potential of such random lasers is also demonstrated.
Highlights
R ANDOM distributed feedback (RDFB) fiber lasers have attracted a lot of interest from the scientific community thanks to simple and cheap cavity schemes, as well as highly efficient generation of laser radiation in a wide wavelength range [1]
A relatively narrow linewidth (0.01–0.1 nm) and high slope efficiency have been obtained for RDFB fiber lasers, the long-length cavity is the main drawback of these types of lasers
We report on the development of extremely short (~10 cm) artificial random Rayleigh reflector with low losses and its implementation as a distributed output mirror in Er-doped fiber lasers with a half-open cavity
Summary
R ANDOM distributed feedback (RDFB) fiber lasers have attracted a lot of interest from the scientific community thanks to simple and cheap cavity schemes, as well as highly efficient generation of laser radiation in a wide wavelength range [1]. A fiber Bragg grating (FBG) with random variation in period and amplitude (coupling coefficient) along the optical axis [3, 10, 11], an array of FBGs with random intervals and reflection coefficients [12, 13], and point reflectors forming Fabry-Perot interferometers [14] could be used as such randomized reflector In these lasers both multi- and single-frequency generation regimes are observed depending on the resonator length, pump power, and the type of random structure providing distributed feedback. Due to the feedback arising at the reflection from multiple FBGs, the authors managed to reach the laser generation threshold at a pump power of 100 mW while the generation linewidth amounted to 300 Hz. In [10], long (20–30 cm) random FBGs were inscribed in an erbium-doped fiber with small phase errors randomly but continuously distributed along the grating profile. Single-frequency, narrowlinewidth and tunable operation regimes of such lasers have been demonstrated and optimized
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