Review of fiber superluminescent pulse amplifications

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 µm and a mode-field diameter of 180 µm 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.

Experimental Identification of Ultrafast Reverse Hole Transfer at the Interface of the Photoexcited Methanol/Graphitic Carbon Nitride System

“…3-4 ps) accounts for the subsequent exciton trapping from the band edges to certain band-gap trap states. [28,29] Care must be taken to the late-time kinetics in Figure 1c,w hich show ad istinct difference for the two systems:I nc ontrast to the continued relaxation for H 2 O/g-C 3 N 4 (with atime constant of > 2.3 ns reflecting the slow exciton recombination), [28,29] there emerges at urn-around PB growth beyond about 20 ps for CH 3 OH/g-C 3 N 4 .Such akinetic growth process features atime constant of 411 AE 32 ps and converges to an egative plateau (with am agnitude of about 4mOD) indicating av ery long, subsequent relaxation (which will eventually recover to null TA signal, ap rocess not recorded here owing to the optical delay scanning limit of our pump-probe spectrometer,c a. 8ns).…”

In-band pumping avenue based high power superfluorescent fiber source with record power and near-diffraction-limited beam quality

“…Thanks to the superior features on short coherence length, high temporal and thermal stability, broad spectral coverage and good beam quality, superfluorescent fiber sources (SFSs) have drawn great attention in the past decades [1][2][3][4] , and researches, including spectral evolution [5] , operating wavelength expansion [6,7] , and potential application exploration [8,9] have been widely investigated. Especially, the utilizations of high power SFSs in many fields, such as mid-infrared laser and supercontinuum generation [10,11] , random fiber laser, and Raman fiber laser pumping [12][13][14] and spectral beam combination [15] , have been demonstrated in recent years for its inherent unique incoherence and high temporal stability characteristics.…”