Passively Q-switched of EDFL employing multi-walled carbon nanotubes with diameter less than 8 nm as saturable absorber

Abstract

Abstract. The paper demonstrates passively Q-switched erbium-doped fiber laser implementing multiwalled carbon nanotubes (MWCNTs) based saturable absorber. The paper is the first to report the use of the MWCNTs with diameter less than 8 nm as typically, the diameter used is 10 to 20 nm. The MWCNTs is incorporated with water soluble host polymer, polyvinyl alcohol (PVA) to produce a MWCNTs polymer composite thin film which is then sandwiched between two fiber connectors. The fabricated SA is employed in the laser experimental setup in ring cavity. The Q-switching regime started at threshold pump power of 103 mW and increasable to 215 mW. The stable pulse train from 41.6 kHz to 76.92 kHz with maximum average output power and pulse energy of 0.17 mW and 3.39 nJ are produced. The shortest pulse width of 1.9 s is obtained in the proposed experimental work, making it the lowest pulse width ever reported using MWCNTs-based saturable absorber.

All-fiberized amorphous carbon nitride (a-CNx) based passive Q-switcher

“…The sharp drop in the pulse duration as the pump power is tuned from 10.58 mW to 19.64 mW is due to the threshold intensity of the SA being reached [20]. The shortest pulse duration recorded in the experiment is lower than the ones reported in works related to carbon based SAs such as graphene and carbon nanotubes [16][17][18][19].…”

“…As compared to other carbon based SAs, the minimum pump power required to induce a Q-switching operation is tremendously lower than that reported in [8][9] as well as when using other carbon based SAs [16][17][18][19]. The Q-switching operation is kept stable as the tunable pump power is increased steadily over 90 mW.…”

“…A high pulse energy is also recorded at 136.77 nJ. When compared to the Q-switching works on carbon based SAs [16][17][18][19], this work yielded a higher peak power and/or pulse energy with a relatively low pulse duration, in the same wavelength region. The first beat node at the repetition rate of 57.99 kHz is approximately 48 dB, as shown in Figure 12, indicating that the pulse produced is stable with low amplitude noise fluctuations.…”

“…At maximum input pump power, the repetition rate is recorded at 57.99 mW with corresponding pulse duration of 1.36 μs. The repetition rate of 57.99 mW is higher, it not comparable to that of graphene oxide and carbon nanotubes based SAs [16][17][18][19]. 11 shows how repetition rate and pulse width, as well as the instantaneous peak power and pulse energy, respectively, are related to the input pump power.…”