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.

Abstract: A side grating based light coupling system comprises an optical fiber, a side grating disposed on one side of the lateral wall of the optical fiber, and a laser array disposed adjacent to the other side of the lateral wall of the optical fiber. The side grating comprises a plurality of grating elements arranged in a non-uniform arrangement. The laser array for generating a laser beam towards and passes through the optical fiber, and the laser beam is converted into at least one laser beam through the plurality grating elements. The diffraction efficiencies of the converted laser beams are different. The converted laser beams propagate inside the optical fiber based on total internal reflection. The plurality of grating elements of the side grating are heterogeneous arrangement without loading the optical collimating lens, and can reduce scattering loss by controlling the asymmetric diffraction efficiency, to improve optical coupling efficiency.