Micro-sized lasers completely embedded within single live cells (1) and biological tissues (2) have been demonstrated. The lasers were made out of solid beads including biocompatible and biodegradable materials. The lasers inside cells can act as very sensitive sensors, enabling us to better understand cellular processes. Further, lasers were used for cell tagging. Each laser within a cell emits light with a slightly different fingerprint that can be easily detected and used as a barcode to tag the cell (3), providing the ability the study cell migration including cancer metastasis. We have also demonstrated that small lasers embedded in the sample can be used for novel nonlinear microscopy, including super resolution imaging (4). The narrow spectra and nonlinear power dependence of stimulated emission from the laser particles yield optical sectioning, sub-diffraction resolution, and low out-of-focus background. Small lasers embedded into cells and tissues may enable new diagnostic, treatment and imaging tools in medicine and biology (5).

(1) M. Humar and S. H. Yun. Intracellular microlasers, Nature Photonics 9, 572 (2015). (2) M. Humar, A. Dobravec, X. Zhao, S. H. Yun. Biomaterial microlasers implantable in the cornea, skin, and blood. Optica 4, 1080-1085 (2017). (3) M. Humar, A. Upadhya, S.H. Yun. Spectral reading of optical resonance-encoded cells in microfluidics. Lab on a Chip 17, 2777-2784 (2017). (4) S. Cho, M. Humar, N. Martino, S. H. Yun, Physical Review Letters 117, 193902 (2016). (5) M. Humar, S.J.J. Kwok, S.Y. Cho, M. Choi, A.K. Yetisen, S.H. Yun. Toward biomaterial-based implantable photonic devices. Nanophotonics 5, 60–80 (2016).