Stokes mode Raman random lasing in a fully biocompatible medium.

We demonstrate for the first time, to the best of our knowledge, Raman random lasing in a continuous-wave (CW) excited, completely biocompatible and biodegradable carrot medium naturally composed of fibrous cellulose scattering medium and rich carotene Raman gain medium. The CW-laser-induced photoluminescence threshold and linewidth analysis at the Stokes modes of carotene show a characteristic lasing action with a threshold of 130  W/cm2 and linewidth narrowing with mode Q factor up to 1300. Polarization study of output modes reveals that lasing mode mostly retains the source polarization state. A neat and interesting linear temperature dependence of emission intensity is also discussed. Easy availability, biocompatibility, excitation-dependent emission wavelength selectivity, and temperature sensitivity are hallmarks of this elegant Raman laser medium with strong potential as an optical source for applications in bio-sensing, imaging, and spectroscopy.