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Tin Phthalocyanine as Q-switcher in Fiber Laser Cavity
Salam M. Azooz, Sameer Salam, Abdulkadir Mukhtar Diblawe, Ahmad R. Muhammad and Sulaiman Wadi Harun
Tin Phthalocyanine (SnPc), an organic compound, presents significant promise for pulsed laser applications owing to its excellent nonlinear optical absorption properties within the 1.55 μm region. A SnPc film-based saturable absorber (SA), boasting a modulation depth of 19%, was produced by incorporating commercial SnPc particles into a polyvinyl alcohol (PVA) matrix. Experimental investigations employing the SnPc film as a switching device within two distinct fiber laser cavities exhibited typical Q-switched laser behavior. The resulting emission occurred at wavelengths of 1531.8 nm and 1564.31 nm for Erbium-doped fiber lasers (EDFLs) configured with Erbium-doped fiber (EDF) lengths of 0.8 m and 1.8 m, respectively. With a 0.8 m long EDF, the laser achieved a maximum repetition rate of 89.3 kHz, a minimum pulse width of 1.82 µs, and a maximum pulse energy of 39.6 nJ. Conversely, utilizing a 1.8 m long EDF, the highest attained single pulse energy reached 66.3 nJ, corresponding to a pulse duration, repetition rate, and average output power of 3.22 μs, 84.9 kHz, and 5.6 mW, respectively. The elongated EDF resulted in improved pulse energy, albeit at the expense of a reduced maximum repetition rate and increased minimum pulse width. This outcome can be attributed to enhanced population inversion within the longer active fiber, subsequently augmenting output power but diminishing the loss modulation or Q-switching effect within the EDFL cavity. The SnPc SA demonstrates characteristics of high modulation depth, low cost, and excellent flexibility, rendering it suitable for optical applications in near-infrared.
Keywords: Q-switching, SnPc, organic saturable absorber, Erbium-doped fiber laser