Zinc phthalocyanine thin film as saturable absorber for Q-switched pulse generation

Abstract

Abstract This paper demonstrated the use of Zinc phthalocyanine (ZnPc) thin film as saturable absorber (SA) to generate Q-switched pulse train in erbium-doped fiber laser (EDFL) cavity. The film was prepared in three methods; ZnPc was embedded into, casted onto and spin-coated onto the polyvinyl alcohol (PVA) film and the samples are referred to embedding ZnPc:PVA, casting ZnPc/PVA, and spin-coating ZnPc/PVA, respectively in this paper. The SA was inserted between two optical fiber ferrules in the laser cavity. The Q-switched fiber laser operates at a wavelength of 1561.4, 1560.4 and 1559.5 nm for embedding ZnPc:PVA, casting ZnPc/PVA, and spin-coating ZnPc/PVA SAs respectively. The pulse repetition rate increases from 25.19 to 48 kHz, 30.3 to 43 kHz, and 21.5 to 32.2 kHz as the pump power rises from 115.8 to 148 mW, 119 to 141 mW, and 109.6 to 135 mW for the SA fabrication methods of ZnPc:PVA, casting ZnPc/PVA, and spin-coating ZnPc/PVA, respectively. However, the pulse width decreases from 8.28 to 3.6 µs for embedding ZnPc:PVA, 10.8 to 4.9 µs for casting ZnPc/PVA, and 12.3 to 6 µs for spin-coating ZnPc/PVA. The results indicate that the ZnPc materials is feasible for use as SA in realizing a reliably stable and flexible Q-switching pulse lasers for 1.5 µm region. The maximum pulse energies are calculated to be 71, 32 and 50 nJ for the three SA fabrication methods of ZnPc:PVA, casting ZnPc/PVA, and spin-coating ZnPc/PVA. To the best of the authors’ knowledge, this is the first time ZnPc material is used as a SA device for a stable Q-switched laser pulse operation.