Abstract
High coherence of the laser is indispensable light sources in modern long or short-distance imaging systems, because the high coherence leads to coherent artifacts such as speckle that corrupt image formation. To deliver low coherence pulses in fiber amplifiers, we utilize the superluminescent pulsed light with broad bandwidth, nonlongitudinal mode structure and chaotic mode phase as the seed source of the cascaded fiber amplifiers. The influence of fiber superluminescent pulse amplification (SPA) on the limitations of the performance is analyzed. A review of our research results for SPA in the fibers are present, including the nonlinear theories of this low coherent light sources, i.e., self-focusing (SF), stimulated Raman scattering (SRS) and self-phase modulation (SPM) effects, and the experiment results of the nanosecond pulses with peak power as high as 4.8 MW and pulse energy as much as 55 mJ. To improve the brightness of SPA light in the future work, we introduce our novel evaluation term and a more reasonable criterion, which is denoted by a new parameter of brightness factor for active large mode area fiber designs. A core-doped active large pitch fiber with a core diameter of $190~\unicode[STIX]{x03BC}\text{m}$ and a mode-field diameter of $180~\unicode[STIX]{x03BC}\text{m}$ is designed by this method. The designed fiber allows near diffracted limited beam quality operation, and it can achieve 100 mJ pulse energy and 540 W average power by analyzing the mode coupling effects induced by heat.
Highlights
Fiber lasers and amplifiers develop rapidly due to the demands of high energy and high peak power pulses in industries[1] and scientific researches[2]
The key technology in this progress is the development of larger mode field area fibers (especially very large mode field area (VLMA) fibers with mode-field diameters (MFDs) beyond 50 μm) which is an effective way to increase the storage energy and mitigate intensity-related nonlinear effects[3]
We have reported the generation of nanosecond pulses with 55 mJ energy and 4.8 MW peak power in a multistage fiber amplifier system[16], which is seeded with 10 nm broadband pulses from a superluminescence diode (SLD)
Summary
Fiber lasers and amplifiers develop rapidly due to the demands of high energy and high peak power pulses in industries[1] and scientific researches[2]. To improve the peak power further, we developed a new technology, i.e., utilizing broadband superluminescent pulsed light, such as the superluminescent diode light, super fluorescence or spontaneous emission light, as the seed source of the cascaded fiber amplifiers in as early as 2009 under the support of National High Technology Research and Development Program of China. We termed it as a superluminescent pulse amplification (SPA) technology. The designed fiber allows near diffracted limited beam quality operation, and it can achieve 100 mJ pulse energy and 540 W average power by analyzing the mode coupling effects induced by heat
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