High-power low spatial coherence random fiber laser

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 highpower 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.

Tailoring of spatial coherence in a multimode fiber by selectively exciting groups of eigenmodes

“…At the input part of the MMF, the stress is exerted by adding weights (stepped by 100 g) on the fiber. It is worth noting that by radially exerting stress on the MMF, the total injected laser power keeps unchanged comparing with our previous approach [29] and the output power of the MMF is also experimentally verified to be unchanged, which means no evident attenuation is induced to the light propagating here. In this way, only the variation of modal power distribution affects the output and the characteristics of spatial coherence.…”

“…However, it is quite challenging to precisely control the modal power distribution of all the considered modes in an individual profile. It has been verified experimentally that more effective spatial eigenmodes can be excited with the increasing of the laser's power [29]. Here, qualitative mode power transfer between the lower and higher order modes is implemented through radially exerted stress on Fig.…”

High‐Power Multimode Random Fiber Laser for Speckle‐Free Imaging

“…[ 1–3 ] Benefiting from cavity‐free configuration and wavelength flexibility of stimulated Raman scattering, RFL is inherently characteristic with high stability, low noise, high power, and efficiency, making it suitable for optical communication and sensing, [ 4,5 ] high efficiency/high power applications, [ 6,7 ] and imaging. [ 8–10 ] Among all of the above potential applications, achieving RFL with high efficiency/high power makes great significance, because ultra‐high optics‐conversion efficiency of short‐cavity RFL could even approach the quantum limit. [ 11 ] A great number of researches based on high‐power RFL have been carried out in recent years.…”

“…Speckle‐free imaging is another fascinating application of RFL. [ 8,9,14,15 ] Although traditional lasers have the advantage of high brightness, they are poorly suitable for a full‐field speckle‐freeimaging application due to their high spatial coherence derived from coherent feedback in regular cavities, which leads to speckles and decreases the imaging quality. Hence it is crucial for light sources to possess both low spatial coherence and high brightness properties for speckle‐free imaging.…”

Dental Imaging With Near-Infrared Transillumination Using Random Fiber Laser

“…Random fiber laser (RFL) is akin to the RL, being the quasi one-dimensional version of the RL, which possesses the same nonconventional laser characteristic, rather than by the fixed mirror or fiber Bragg grating. The feedback is provided by a scattering medium [21][22][23][24][25], apart from advantages in RL, RFL has the qualities of quasi one-dimension and high output power, flexible lasing wavelength, and robust structure. The RFL is demonstrated to be suitable for high power low-coherence full-field real-time speckle free imaging [26][27][28][29].…”