Simultaneous Realization of a Coherent Perfect Absorber and Laser by Zero-index Media with both Gain and Loss (2016)
Bai, P., Ding, K., Wang, G., Luo, J., Zhang, Z., Chan, C.T., Wu, Y. and Lai, Y.
Physical Review A. 94(6). doi:10.1103/PhysRevA.94.063841