Development of Figure-8 Variable Pulse Width Fiber Laser using Coherent Resonator Coupling Technology

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 compornents 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 diffarence decreases coupled longitudinal modes and narrows spectral width (Δν). Thus, pulse width (Δt) is widened according to equation (1).