Performance of graphene nanopowder-polyvinyl alcohol in optical pulse generation at 1.5 micron region

This paper explains the performance of a graphene nanopowder (GNP) based saturable absorber (SA) at the 1.5-micron region which is prepared by dissolution in polyvinyl alcohol (PVA) polymer. Two different GNP flake thicknesses (AO2-8 nm and AO4-60 nm) are tested. By applying a solution casting method, three weight ratios of GNP to PVA (12.04, 8.03 and 3.11 wt.%) have been prepared and fabricated as a thin composite film. To characterize the SA performance, a 4 mm2 area of thin GNP-PVA film is embedded in a 14 meter long ring cavity with a 3 meter Erbium doped fiber (EDF) as a gain medium. Our characterization results show that the thin GNP-PVA film acts as a Q-switcher which produces stable laser pulses for 12.04 wt.% with a maximum repetition rate of 39.22 kHz and a shortest pulse width of 11.79 µs. Meanwhile, unstable Q-switched pulses of 8.03 wt.% and 3.11 wt.% have been observed with recorded signal to noise ratio (SNR) of only 21 dB and 17 dB, respectively. The threshold pumping power for Q-switched lasing to emerge is recorded as low as 30 mW. Apparently, it shows that GNP concentration and flakes thickness in a fabricated SA composite plays a vital role in the performance of a generated Q-switch laser, particularly at the 1.5 µm region