Abstract
The study presents a novel demonstration of a passively mode-locked erbium-doped fiber laser (EDFL) that is based on a silicon carbide (SixC1−x) saturable absorber. When the C/Si composition ratio is increased to 1.83, the SixC1−x film transforms from two-photon absorption to nonlinear saturable absorption, and the corresponding value reaches −3.9 × 10−6 cm/W. The Si-rich SixC1−x film cannot mode lock the EDFL because it induced high intracavity loss through two-photon absorption. Even when a stoichiometric SiC is used, the EDFL is mode locked, similar to an EDFL operating under weak nonlinear-polarization-rotation condition. A C-rich SixC1−x film containing sp2-orbital C–C bonds with a linear absorbance of 0.172 and nonlinear absorbance of 0.04 at a 181 MW/cm2 saturation intensity demonstrates nonlinear transmittance. The C-rich SixC1−x saturable absorber successfully generates a short mode-locked EDFL pulse of 470 fs. The fluctuation of the pulse-train envelope dropps considerably from 11.6% to 0.8% when a strong saturable-absorption-induced self-amplitude modulation process occurs in the C-rich SixC1−x film.
Highlights
Because of its high thermal stability and high chemical inertness[29], nonstoichiometric silicon carbide (SixC1−x) is a candidate for a high-damage-threshold material, with a damage threshold that can reach up to 40 TW/cm[230]
The study presents a novel demonstration of using a plasma-enhanced chemical vapor deposition (PECVD)-grown SixC1−x saturable absorber for implementing passive mode-locked EDFLs
When the Si-rich SixC1−x film is used as the saturable absorber, the EDFL cannot be mode locked at the same effective gain because the Si-rich SixC1−x film causes higher intracavity linear losses
Summary
Because of its high thermal stability and high chemical inertness[29], nonstoichiometric silicon carbide (SixC1−x) is a candidate for a high-damage-threshold material, with a damage threshold that can reach up to 40 TW/cm[230]. This material has already been considered for high-temperature and high-power electronics and has a wide variety of optoelectronic applications[31,32]. The current study presents a novel demonstration of the use of a nonstoichiometric SixC1−x film as a saturable absorber for passively mode-locked fiber lasers. The effect of sp2-orbital C–C bonds on the nonlinear transmittance of SixC1−x was characterized to determine methods through which the phase-focusing performance of mode-locked EDFLs can be improved according to C-rich SixC1−x films
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