[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Development of Figure-8 Variable Pulse Width Fiber Laser using Coherent Resonator Coupling Technology

摘要： A femtosecond pulsed laser has an extremely short pulse width and high peak power and is used for the field of microfabrication. On the other hand, laser cutting and drilling requires picosecond pulsed laser with high pulse energy. In general, a diffraction grating or a band pass filter is used to control pulse width. However, these components are not affordable and the optical system with them becomes complicated. Therefore, we have developed all fiber variable pulse width laser by applying a coherent resonator coupling technology that increases the output power by coupling the phases of longitudinal modes generated by sharing an output coupler in multiple laser resonators. In the coherent resonator coupling, resonator length difference decreases coupled longitudinal modes and narrows spectral width (?ν). Thus, pulse width (?t) is widened according to equation (1). ?t ? ?ν = const (1) We will describe the configuration of the resonator used in the experiment. A resonator coupling technology is applied to a figure-8 fiber laser. The figure-8 fiber laser is a ring resonator that contains a nonlinear optical loop mirror. It operates as a resonator only when a phase difference occurs between the clockwise light that travels through the loop of the mirror and the counter-clockwise one. The phenomenon functions as a saturable absorption effect and generates femtosecond pulses. Further, we use a variable delay line in one of the resonator to control resonator length difference. Figure 1 shows the configuration of the figure-8 variable pulse width fiber laser and Fig. 2 shows the configuration of a nonlinear optical loop mirror.