[1] M. E. Fermann and I. Hartl, Nat. Photon. 7, 868 (2013).
[2] S. D. Jackson, Nat. Photon. 6, 423 (2012).
[3] H. Lu, P. Zhou, H. Xiao, X. Wang, and Z. Jiang, Chin. Opt. Lett. 10, 051403 (2012).
[4] C. Guo, D. Shen, J. Long, and F. Wang, Chin. Opt. Lett. 10, 091406 (2012).
[5] M. A. Solodyankin, E. D. Obraztsova, A. S. Lobach, A. I. Chernov, A. V. Tausenev, V. I. Konov, and E. M. Dianov, Opt. Lett. 33, 1336 (2008).
[6] L. E. Nelson, E. P. Ippen, and H. A. Haus, Appl. Phys. Lett. 67, 19 (1995).
[7] Q. Wang, J. Geng, Z. Jiang, T. Luo, and S. Jiang, IEEE Photon. Technol. Lett. 23, 682 (2011).
[8] L. E. Nelson, D. J. Jones, K. Tamura, H. A. Haus, and E. P. Ippen, Appl. Phys. B 65, 277 (1997).
[9] F. o. Ilday, J. R. Buckley, W. G. Clark, and F. W. Wise, Phys. Rev. Lett. 92, 213902 (2004).
[10] A. Chong, J. Buckley, W. Remomger, and F. Wise, Opt. Express 14, 10095 (2006).
[11] L. Zhao, D. Tang, H. Zhang, T. Cheng, H. Y. Tam, and C. Lu, Opt. Lett. 32, 1806 (2007).
[12] S. Kobtsev, S. Kukarin, and Y. Fedotov, Opt. Express 16, 21936 (2008).
[13] A. Wienke, F. Haxsen, D. Wandt, U. Morgner, J. Neumann, and D. Kracht, Opt. Lett. 37, 2466 (2012).
[14] F. Haxsen, D. Wandt, U. Morgner, J. Neumann, and D. Kracht, Opt. Express 18, 18981 (2010).
[15] W. H. Renninger, A. Chong, and F. W. Wise, IEEE J. Sel. Top. Quantum Electron. 18, 289 (2012).
[16] A. Cabasse, G. Martel, and J. L. Oudar, Opt. Express 17, 9537 (2009).
[17] A. Szabo and Z. Varallyay, IEEE Photon. Technol. Lett. 24, 122 (2012).
[18] G. R. Jacobovitz–Veselka, U. Keller, and M. T. Asom, Opt. Lett. 17, 1791 (1992).
[19] H. Zhang, D. Tang, L. Zhao, Q. Bao, K. P. Loh, B. Lin, and S. C. Tjin, Laser Phys. Lett. 75, 91 (2010).
[20] N. Nishizawa, Y. Seno, K. Sumimura, Y. Sakakibara, E. Itoga, H. Kataura, and K. Itoh, Opt. Express 16, 9429 (2008).
[21] A. Martinez and Z. P. Sun, Nat. Photon. 7, 842 (2013).
[22] Q. Bao, H. Zhang, Y. Wang, Z. Ni, Y. Yan, Z. Shen, K. P. Loh, and D. Tang, Adv. Funct. Mater. 19, 3077 (2009).
[23] C. Zhao, H. Zhang, X. Qi, Y. Chen, Z. Wang, S. Wen, and D. Tang, Appl. Phys. Lett. 101, 211106 (2012).
[24] Y. An, D. Shen, W. Zhao, and J. Long, Opt. Commun. 285, 1949 (2012).
[25] H. Liu, K. Kieu, S. Lefrancois, W. H. Renninger, A. Chong, and F. W. Wise, in Proceeding of CLEO: Science and Innovations, Optical Society of America (2011).
[26] H. Zhang, D. Tang, L. Zhao, X. Wu, and H. Y. Tam, Opt. Express 17, 455 (2009).
[27] F. X. Kartner, J. A. der Au, and U. Keller, IEEE J. Sel. Top. Quantum Electron. 4, 159 (1998).
