Abstract
A high-power multi-transverse modes random fiber laser (RFL) is investigated by combining a master oscillator power-amplifier (MOPA) configuration with a segment of extra-large mode area step-index multimode fiber (MMF). Spatial coherence of the high-power multi-transverse modes RFL has been analyzed, which shows that speckle contrast is reduced dramatically with the output power increasing. In this way, considerably low speckle contrast of ~0.01 is achieved under high laser power of ~56 W, which are the records for multi-transverse modes RFLs in both spatial coherence and output power. This work paves a way to develop high-power RFLs with very low spatial coherence for wide-range speckle-free imaging and free-space communication applications.
Highlights
Random fiber lasers (RFLs) based on random distributed Rayleigh scattering and stimulated Raman scattering (SRS) are favorable for their stable output in time domain, simplicity in structure and reliability in practical applications [1,2,3]
A 1064 nm 1:99 coupler is temporarily connected after the 1064 nm ISO of the RFL seed part to measure the optical spectrum through the 1% port
The spectrum becomes stable after the pump power is higher than the threshold and the bandwidth gradually broadens with the increase of pump power
Summary
Random fiber lasers (RFLs) based on random distributed Rayleigh scattering and stimulated Raman scattering (SRS) are favorable for their stable output in time domain, simplicity in structure and reliability in practical applications [1,2,3]. Among all the potential applications, RFL with short fiber length is preferable for achieving highly efficiency/power output, while the optical-to-optical efficiency could approach the quantum limit [4,5]. Numerous researches on high-power RFLs have been put forward in recent years [6,7,8,9]. The output power of RFL based on short fiber length has been continuously promoted with the optimization of laser structures. The spectral bandwidth of the RFL has been demonstrated to be well maintained during high-power amplification in a master oscillator power-amplifier (MOPA) configuration that generates kilowatt-level RFL output [11]
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