Putting Spin into Lasers

Considering circular polarization, an optical analog of electron spin, semiconductor lasers with spin-polarized carriers can open up unexplored possibilities for spin-controlled devices. Once spin-polarized carriers are introduced in the gain region of lasers, by circularly polarized light or electrical spin-injection, the operation of such spin-lasers should be revisited to incorporate their novel properties. Spin-polarized carriers can enhance the performance of lasers for communication and signal processing [1]. In the steady-state, such spin-lasers already demonstrated a lower threshold current for the lasing operation [2] compared to their conventional (spin-unpolarized) counterparts, however, the most exciting opportunities come from their dynamical operation. We reveal that the spin modulation in lasers can lead to an improvement in the two key figures of merit: enhanced bandwidth [3] and reduced parasitic frequency modulation---chirp [4]. Analyses are carried out under generalized modulation regimes we propose. Different mechanisms for quantum dots and quantum wells as a gain medium are also discussed and we provide a mapping between the two gain media. Spin states in quantum dots may also enable elusive phonon lasers [5], which emitts coherent phonons instead of photons. This work was performed in collaboration with R. Oszwa\l dowski, C. G{\o}thgen, G. Boeris, and I. \v{Z}uti\'{c}. \\[4pt] [1] J. Sinova and I. \v{Z}uti\'{c}, Nature Materials 11, 368 (2012); Handbook of Spin Transport and Magnetism, edited by E. Y. Tsymbal and I. \v{Z}uti\'{c} (CRC Press, New York, 2011). \\[0pt] [2] J. Rudolph et al., Appl. Phys. Lett. 87, 241117 (2005); M. Holub et al, Phys. Rev. Lett. 98, 146603 (2007); S. Hovel et al., Appl. Phys. Lett. 92, 041118 (2008); S. Iba, et al., Appl. Phys. Lett. 98, 08113 (2011); M. Holub and B. T. Jonker, Phys. Rev. B 83, 125309 (2011). \\[0pt] [3] J. Lee, W. Falls, R. Oszwa\l dowski, and I. \v{Z}uti\'{c}, Appl. Phys. Lett. 97, 041116 (2010); J. Lee, R. Oszwa\l dowski, C. G{\o}thgen, and I. \v{Z}uti\'{c}, Phys. Rev. B 85, 045314 (2012). \\[0pt] [4] G. Bo\'{e}ris, J. Lee, K. V\'{y}born\'{y}, and I. \v{Z}uti\'{c}, Appl. Phys. Lett. 100, 121111 (2012). \\[0pt] [5] A. Khaetskii, V. N. Golovach, X. Hu, and I. \v{Z}uti\'{c}, Phys. Rev. Lett. 111, 186601 (2013).