Getting to the brain

To realize these exciting applications, many challenges have to be overcome, such as the development of even smaller lasers with lower threshold, higher brightness and higher stability in the biological environment.The tasks include the search for more efficient rare-earth doped nanomaterials as the gain medium, high refractive index materials to enhance Q-factor in biological samples, and the development of materials fabrication procedures to make smaller and integrated resonators.For example, the large variation in lasing threshold among 22 demonstrated microsphere lasers, reported by Fernandez-Bravo et al., suggests that alternative fabrication approaches have to be explored for better control of nanoparticle concentration and coating.With many advances being made in the design and fabrication of a variety of micro-and nanoscale cavities 2 , for example, disks, tubes and rings, that accommodate WGM with high Q-factors, the challenge broadly lies in the seamless integration of a cavity with a gain medium.With the landmark work reported by Fernandez-Bravo et al., we expect a new wave of technology integration and interdisciplinary collaborations between material science, photonics, nanotechnology and device engineering to develop a new set of cell biology methods and analytical devices.