Multimode Random Fiber Laser for Speckle-Free Imaging

Light sources with high radiance are increasingly required for full-field real-time imaging. Conventional lasing sources are poorly suited for such imaging due to their high spatial or temporal coherence, which generates a speckle that deteriorates image quality. Here, a random fiber laser with multitransverse modes is used as an illumination light source to effectively reduce the speckle in imaging. Low spatial coherence and low temporal coherence of the random fiber laser give birth to significant reduction in the speckle. Under the power-limited condition, the multimode random fiber laser is verified to have a comparable or even better imaging quality compared to a multimode amplified spontaneous emission source. Furthermore, its potential to generate ultrahigh power of up to hundreds of Watts with extremely-high spectral density would make a breakthrough in the development of a new generation of high-power low-coherence light sources for many speckle-free imaging applications, where conventional light sources are not usable. As the multimode random fiber laser can naturally inherit all the advantages of single-mode random fiber lasers, including flexible wavelength, robust structure, and high power, this paper may provide a platform to develop powerful low-coherence light sources to meet wide range requirements of the full-field real-time speckle-free imaging.