NSF Award
2337595
Nontechnical Description:<br/>Some of the most brilliant colors in nature are not caused by light-absorbing dyes or pigments, but rather from the very microscopic structure of objects. Many tropical fish display beautiful iridescent colors through the interference of reflected light waves from small planar structures inside specialized cells called iridophores. These reflective structures have similarities to modern microscopic laser technologies. Instead of reflecting light, iridophore cells can be infused with fluorescent molecules and emit light. The structures inside the iridophores cause light to bounce around for long periods of time which causes the feedback necessary for laser emission at the microscopic scale. The project’s goals are to better understand laser light scattering and emission from iridescent biological structures and use this information as a tool to gain new insights surrounding the microscopic structures found in some specialized cells. To this end, the underlying physics of laser light emitted from the iridophores found in two different fish species will be probed using light-based experimental methods as well as atom-scale tipped cantilevers and beams of electrons. Models will be developed to gain a deeper understanding of the observed phenomena. Understanding laser emission from biological media can potentially impact the fields of biology, laser physics, materials science, and medicine. Research opportunities, critical to training future scientists and engineers, will be created specifically for undergraduate and high school students through this proposal. <br/><br/>Technical Description:<br/>The freshwater fish, Paracheirodon innesi, and the marine fish invasive to Hawaiian reefs, Cephalopholis argus, have specialized chromatophore cells called iridophores that exhibit iridescent colors caused by the interference of reflected light. The scientifically verified multilayer guanine/cytoplasm structures in Paracheirodon innesi that cause the colorful appearance can act as a multilayer distributed feedback laser architecture. Gain will be introduced into the cytoplasm layers through diffusion of fluorescent chromophores with high quantum yields that are passed across the lipid bilayer membrane through various methods. The laser threshold behavior and slope efficiencies will be studied in the iridophores of both species as well as the laser emission’s tunability from induced physical changes in the photonic crystal structures. The guanine platelet dimensions will determine the structure of individual guanine crystal platelets, and transmission electron microscopy techniques will image cross sections of the photonic crystal structures. Physics-based phenomenological models will be developed from physical, electron beam, linear optical, and laser measurements. The laser emission results will be tested against finite-difference time-domain simulations using cavity information gained from atomic force microscopy and transmission electron microscopy studies. The emission characteristics in both fish species will be compared with established results for inorganic, organic, and biological lasers. From a fundamental perspective, new laser architectures for tunable lasers could result from this study of lasing in complex biological architectures. From a systems perspective, the investigation will further our understanding of the production and manipulation of coherent light in animals. From an engineering perspective, new biocompatible and/or biogenic designs for microscopic lasers will be realized.<br/><br/>This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
