Recent Advances and Challenges in Ultrafast Photonics Enabled by Metal Nanomaterials

Nanomaterials with outstanding optical properties are widely used in ultrafast photonics. Especially, metal nanomaterials have attracted increasing attention in recent years owing to the surface plasmon resonance that further enhances their nonlinear optical response, making them suitable for generating ultrafast pulses in a wide range of wavebands. Herein, the fabrication and integration processes of typical metal nanomaterials such as gold, silver, and copper, as well as their applications in ultrafast lasers are reviewed. The synthesis methods of metal nanomaterials, which can be divided into dry and wet methods, are first introduced with their characteristics and advantages summarized. Moreover, the integration approaches that are used to incorporate metal nanomaterials into laser cavities are discussed, where sandwich structure based on polymer film and deposition method, as well as evanescent-wave structure based on D-shaped and tapered fiber are demonstrated. Besides, the state of the art of typical ultrafast lasers enabled by metal nanoparticles is systematically reviewed. Finally, current challenges and perspectives on the development of ultrafast photonics enabled by metal nanomaterials are proposed.