Abstract: A passively Q-switched fiber laser system comprises a pump source and an ring cavity connected with each other. The ring cavity comprises a gain fiber, a directional coupler and a saturable absorber connected in order. The saturable absorber is a quantum-dot polymer composite film, which is fabricated by a simple method comprising steps of: mixing a quantum dot material of lead sulfide (PbS) with a colloidal polymer to form a mixture; and drying the mixture at two different temperatures in two stages respectively. The saturable absorber of the present invention has lower saturating intensity and a plurality of absorption bands comprising 1000 nm to 1100 nm and 1500 nm to 1600 nm. The maximum output power and the maximum pulse energy of the passively Q-switched fiber laser system can be superior to those laser systems using the quantum-dot (QD) polymer composite film as saturable absorber.

Abstract: A passively Q-switched fiber laser system comprises a pump source and an ring cavity connected with each other. The ring cavity comprises a gain fiber, a directional coupler and a saturable absorber connected in order. The saturable absorber is a quantum-dot polymer composite film, which is fabricated by a simple method comprising steps of: mixing a quantum dot material of lead sulfide (PbS) with a colloidal polymer to form a mixture; and drying the mixture at two different temperatures in two stages respectively. The saturable absorber of the present invention has lower saturating intensity and a plurality of absorption bands comprising 1000 nm to 1100 nm and 1500 nm to 1600 nm. The maximum output power and the maximum pulse energy of the passively Q-switched fiber laser system can be superior to those laser systems using the quantum-dot (QD) polymer composite film as saturable absorber.