Short-pulsed Q-switched fiber laser using graphene oxide quantum dots based as saturable absorber

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 $\beta ={-1.178x10}^{-6}\left(m/W\right)$ and a non-linear susceptibility of $Im\left({\chi }^{\left(3\right)}\right)\approx {-1.573x10}^{-7}\left(esu\right)$. 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.

Keywords: Graphene oxide; Nonlinear characterization; Nonlinear susceptibility; Optical fibers; Quantum dots.

Fig. 1

a) FTIR and b) Raman spectra of carbonized PAN fibers at 1100 °C.

Fig. 2

a) TEM micrograph of the GOQDs. Insets (top: size distribution histogram, and bottom: HRTEM micrograph of a GOQD), b) FTIR spectrum of the GOQDs, and c) Raman spectrum of the GOQDs.

Fig. 3

Experimental setup for the photodeposition of GOQDs onto optical fiber end.

Fig. 4

Experimental setup for measurement of the saturable absorption properties of the GOQDs.

Fig. 5

Nonlinear transmission curve of the GOQDs photodeposited onto the optical fiber.

Fig. 6

Experimental setup for fiber pulsed laser using GOQDs as SA.

Fig. 7

Traces of Q-switched laser output pulse train at different pump powers: a) 59.25, b) 87.10, c) 142.80, and d) 170.65 mW, respectively.

Fig. 8

a) Frequency and pulse width as a function of the incident pump power, and b) Output power as a function of pump power.

Fig. 9

Optical spectrum of the output pulse of Q-switched fiber laser.