Application prospects of boron nitride as a novel saturable absorber device for ultrashort pulse generation in fiber lasers

Abstract

Many two-dimensional materials demonstrate good saturable absorption properties. Therefore, these materials are widely used as saturable absorbers (SAs) in mode-locked lasers. However, to date, these materials have not been put into practical use because of their poor physical or chemical characteristics. Boron nitride (BN) is a wide-gap semiconductor similar to SiC; it possesses ideal mechanical strength, good chemical and thermal stability, high thermal conductivity and excellent insulation. BN is also capable of broadband saturable absorption. In this study, a novel SA based on BN was prepared on a fluorine mica (FM) substrate with good optical properties using magnetron sputtering technology. The film was uniformly distributed, and its thickness was controllable. Meanwhile, FM can withstand a high laser power without being damaged due to its good heat dissipation capacity and low insertion loss. This approach provides both the substrate and BN materials with good physical and chemical properties. Using the BN-FM SA device, a passive mode-locked erbium-doped fiber laser is realized. The pulse duration is 237 fs, and the average output power is 35.39 mW. To the best of our knowledge, this is the first time that a BN-FM SA has been used in mode-locked fiber lasers, which complements the possibilities of the BN material in mode-locked lasers for ultrashort pulse generation. Meanwhile, this work supplies an advantageous choice for the preparation of SA devices with stable optoelectronic properties.