(1) Improvement of the intrinsic performance of fiber lasers: Key research priorities in the field of fiber lasers in the future include increasing output power and conversion efficiency, optimizing beam quality, reducing the length of the gain fiber, and enhancing system stability while making the devices smaller and more compact.
(2) Development of novel fiber lasers: In the time domain, mode-locked fiber lasers generating ultrashort pulses with ever-smaller duty cycles have long been a hot topic in laser research; specifically, the development of high-power, femtosecond-scale pulsed fiber lasers remains a long-standing objective. In the frequency domain, broadband and tunable fiber lasers are expected to emerge as a major focus of research.
Research into fiber lasers began as early as the late 1980s. Given their capability to generate ultrashort pulses and their vast potential for practical application, nations worldwide have demonstrated immense enthusiasm for fiber laser research. Compared to other types of lasers, fiber lasers possess distinct advantages, including high reliability, simple structure, low cost, and high conversion efficiency.
Domestic research in this field also commenced relatively early, yielding significant results in both theoretical and experimental domains. However, a substantial gap remains when compared to international standards. In particular, research specifically focused on high-performance fiber lasers remains relatively scarce; furthermore, efforts toward practical commercialization have been insufficient, and the results achieved thus far have not been entirely satisfactory. Consequently, it is imperative to further intensify research into passively mode-locked fiber lasers.
In 1963, Snitzer published the first report on a Nd-doped fiber laser, thereby igniting a surge of research interest in the field. Particularly in recent years-driven by advancements in fiber design and fabrication techniques-the output power of fiber lasers has steadily increased; the continuous-wave (CW) output power of single-fiber devices has risen from the hundred-watt level to the kilowatt level. Concurrently, improvements in the fabrication techniques for high-quality fibers-specifically those featuring large cladding diameters and high numerical apertures-have greatly facilitated efficient coupling with diode pump sources.
The most significant advantage of fiber lasers is their exceptionally high pump efficiency. Typically, the pump conversion efficiency ranges from 70% to 75%, which is substantially higher than that of industrial diode-pumped solid-state lasers (DPSSLs). Such high conversion efficiency reduces the cooling and power requirements of the laser system, enabling a more compact structure compared to traditional solid-state lasers; furthermore, the all-fiber architecture provides a highly robust and reliable packaging design. Moreover, fiber lasers can significantly enhance the quality of the output beam.
Another significant advantage is that fiber laser technology can substantially extend device lifetimes (compared to DPSSLs). This benefit has prompted industrial laser companies to continuously increase their investment in fiber laser technology, as long-term operational reliability is of paramount importance in practical applications. Fiber lasers possess additional advantages as well: since the laser medium itself serves as the waveguide, coupling efficiency is high; fiber lasers can be easily and efficiently integrated with fiber-optic transmission systems; the fiber core can be made extremely narrow, thereby achieving high power density; and the excellent heat dissipation properties of the fiber result in high conversion efficiency and a very low lasing threshold. Finally, fiber lasers cover an exceptionally broad range of output wavelengths-spanning from 400 nm to 3400 nm-capable of meeting diverse application requirements and demonstrating excellent prospects across industrial, commercial, telecommunications, military, and medical sectors.
