Liquid-crystal random fiber laser for speckle-free imaging

Liquid crystal random fiber lasers (LC-RFLs) exhibit low spatial coherence, extraordinary tunability, and high flexibility and are therefore promising for use in imaging and related applications. They nevertheless suffer from ineffective emission along the fiber axis. This work develops an end-emitting LC-RFL that is based on a pump-induced gain–loss structure, which effectively modulates the optical feedback, thereby providing directional random lasing along the fiber. The laser emission comprises ∼10 000 transverse spatial modes that are mutually incoherent, resulting in a negligible speckle contrast of ∼0.7% (far below the speckle-perception threshold of human eyes). The developed LC-RFL is used to perform speckle-free full-field imaging in a setting with strong optical crosstalk in a multimode fiber. Our findings support the potential widespread use of LC-RFL as a spatially incoherent, flexible laser source.