ABSTRACT
In this work, we report the experimental study of a Q-switched optical fiber laser based on graphene oxide quantum dots (GOQDs) as saturable absorber (SA). GOQDs are fabricated by carbonization and exfoliation electrospun polyacrylonitrile (PAN) fibers. The results of Fourier Transform Infrared Spectroscopy (FTIR) showed bands caused by the CHs and C[bond, double bond]O groups associated with the GOQDs. The Raman spectrum showed the typical G and D bands of GOQDs. The size of the GOQDs, calculated by Transmission Electron Microscopy (TEM) was 6 nm; additionally, by high resolution TEM (HRTEM), an interplanar distance of 0.19 nm corresponding to the (002) direction of the graphene oxide was calculated. The SA was achieved using the photodeposition technique of the GOQDs onto the core of a single-mode optical fiber. The nonlinear characterization (NLC) of the GOQDs was carried out using the P-scan technique with a high-gain erbium-doped fiber amplifier (EDFA) at a wavelength of 1550 nm. The obtained results showed a saturable absorption behavior with a value of ß=-1.178x10-6(m/W) and a non-linear susceptibility of Im(χ(3))≈-1.573x10-7(esu). The experimental results of the SA, based on GOQDs as a switching device in a fiber laser, showed a typical behavior of a Q-switched laser by generating a pulsed emission at a wavelength of 1599 nm, a frequency from 2 to 16 kHz, and a maximum average output power of 1.3 mW.
ABSTRACT
The nonlinear optical response of graphene oxide quantum dots (GOQDs) fabricated by the carbonization and exfoliation of electrospun polyacrylonitrile (PAN) fibers is reported. Electrospun and carbonized fibers were characterized by SEM and XPS. SEM micrograph confirmed the formation of PAN fibers of 153.44 ± 6.44 nm, while by XPS the binding energies associated with sp2 and sp3 carbon hybridizations were found, after the carbonization process. On the other hand, the GOQDs obtained were characterized by photoluminescence (PL), UV-Vis, Raman spectroscopy, and High-Resolution Transmission Electron Microscopy (HRTEM). The GOQDs size of 10 nm was estimated by HRTEM. Raman spectroscopy showed the D and G bands associated with the sp2 and sp3 hybridizations of the GOQDs, by PL two energy values of 2.67 and 2.97 eV were calculated. The UV-Vis spectrum showed two absorption bands confirming the presence of GOQDs. The nonlinear characterization was carried out using the P-scan technique, previously photodepositing GOQDs onto an optical fiber, using a coherent radiation source at a wavelength of 1550 nm. The results obtained showed a saturable absorption behavior with a value of ß = - 2.474 × 10 - 4 m / W and a nonlinear susceptibility of χ ( 3 ) ≈ - 7.749 × 10 - 4 ( e s u ) . The results of this work showed that GOQDs obtained can be used for optical switching applications.