[1] T. H. Maiman, “Stimulated optical radiation in ruby,” Nature 187, 493–494 (1960).

[2] U. Keller, “Recent developments in compact ultrafast lasers,” Nature 424, 831–838 (2003).

[3] H. Yu, J. Liu, H. Zhang, A. A. Kaminskii, Z. Wang, and J. Wang, “Advances in vanadate laser crystals at a lasing wavelength of 1 micrometer,” Laser Photon. Rev. 8, 847–864 (2014).

[4] F. Bonaccorso, Z. Sun, T. Hasan, and A. C. Ferrari, “Graphene photonics and optoelectronics,” Nat. Photonics 4, 611–622 (2010).

[5] Y. Shimony, Z. Burshtein, and Y. Kalisky, “Cr4+:YAG as passive Q-switch and Brewster plate in a pulsed Nd:YAG laser,” IEEE J. Quantum Electron. 31, 1738–1741 (1995).

[6] T. Y. Tsai and M. Birnbaum, “Q-switched 2-μm lasers by use of a Cr2+:ZnSe saturable absorber,” Appl. Opt. 40, 6633–6637 (2001).

[7] A. M. Malyarevich, I. A. Denisov, K. V. Yumashev, V. P. Mikhailov, R. S. Conroy, and B. D. Sinclair, “V:YAG–A new passive Q-switch for diode-pumped solid-state lasers,” Appl. Phys. B 67, 555–558 (1998).

[8] U. Keller, D. A. B. Miller, G. D. Boyd, T. H. Chiu, J. F. Ferguson, and M. T. Asom, “Solid-state low-loss intracavity saturable absorber for Nd:YLF lasers: An antiresonant semiconductor Fabry–Perot saturable absorber,” Opt. Lett. 17, 505–507 (1992).

[9] T. T. Basiev, S. B. Mirov, and V. V. Osiko, “Room-temperature color center lasers,” IEEE J. Quantum Electron. 24, 1052–1069 (1988).

[10] U. Keller and A. C. Tropper, “Passively modelocked surfaceemitting semiconductor lasers,” Phys. Rep. 429, 67–120 (2006).

[11] X. P. Hu, P. Xu, and S. N. Zhu, “Engineered quasi-phase-matching for laser techniques [Invited],” Photon. Res. 1, 171–185 (2013).

[12] Y. F. Chen, S. W. Tsai, and S. C. Wang, “High-power diodepumped nonlinear mirror mode-locked Nd:YVO4 laser with periodically-poled KTP,” Appl. Phys. B 72, 395–397 (2001).

[13] Y. H. Liu, Z. D. Xie, S. D. Pan, X. J. Lv, Y. Yuan, X. P. Hu, J. Lu, L. N. Zhao, C. D. Chen, G. Zhao, and S. N. Zhu, “Diode-pumped passively mode-locked Nd:YVO4 laser at 1342 nm with periodically poled LiTaO3,” Opt. Lett. 36, 698–700 (2011).

[14] K. S. Novoselov, V. I. Fal, L. Colombo, P. R. Gellert, M. G. Schwab, and K. Kim, “A roadmap for graphene,” Nature 490, 192–200 (2012).

[15] C. N. R. Rao, A. K. Sood, K. S. Subrahmanyam, and A. Govindaraj, “Graphene: The new two-dimensional nanomaterial,” Angew. Chem.. Int. Ed. Engl., Suppl. 48, 7752–7777 (2009).

[16] S. Z. Butler, S. M. Hollen, L. Cao, Y. Cui, J. A. Gupta, H. R. Gutiérrez, T. F. Heinz, S. S. Hong, J. Huang, A. F. Ismach, E. Johnston-Halperin, M. Kuno, V. V. Plashnitsa, R. D. Robinson, R. S. Ruoff, S. Salahuddin, J. Shan, L. Shi, M. G. Spencer, M. Terrones, W. Windl, and J. E. Goldberger, “Progress, challenges, and opportunities in two-dimensional materials beyond graphene,” ACS Nano 7, 2898–2926 (2013).

[17] M. Xu, T. Liang, M. Shi, and H. Chen, “Graphene-like twodimensional materials,” Chem. Rev. 113, 3766–3798 (2013).

[18] A. K. Geim and K. S. Novoselov, “The rise of graphene,” Nat. Mater. 6, 183–191 (2007).

[19] K. S.Novoselov,D.Jiang,F. Schedin, T. J.Booth, V. V.Khotkevich, S. V. Morozov, and A. K. Geim, “Two-dimensional atomic crystals,” Proc. Natl. Acad. Sci. USA 102, 10451–10453 (2005).

[20] K. S. Novoselov, A. K. Geim, S. V. Morozov, D. Jiang, M. I. Katsnelson, I. V. Grigorieva, S. V. Dubonos, and A. A. Firsov, “Two-dimensional gas of massless Dirac fermions in graphene,” Nature 438, 197–200 (2005).

[21] K. P. Loh, Q. Bao, P. K. Ang, and J. Yang, “The chemistry of graphene,” J. Mater. Chem. 20, 2277–2289 (2010).

[22] A. H. C. Neto, F. Guinea, N. M. R. Peres, K. S. Novoselov, and A. K. Geim, “The electronic properties of graphene,” Rev. Mod. Phys. 81, 109–162 (2009).

[23] P. R. Wallace, “The band theory of graphite,” Phys. Rev. 71, 622–634 (1947).

[24] A. K. Geim and I. V. Grigorieva, “Van der Waals heterostructures,” Nature 499, 419–425 (2013).

[25] Q. H. Wang, K. Kalantar-Zadeh, A. Kis, J. N. Coleman, and M. S. Strano, “Electronics and optoelectronics of two-dimensional transition metal dichalcogenides,” Nat. Nanotechnol. 7, 699– 712 (2012).

[26] Z. He, C. Zhong, S. Su, M. Xu, H. Wu, and Y. Cao, “Enhanced power-conversion efficiency in polymer solar cells using an inverted device structure,” Nat. Photonics 6, 591–595 (2012).

[27] Y. Zhang, K. He, C. Z. Chang, C. L. Song, L. L. Wang, X. Chen, J. F. Jia, Z. Fang, X. Dai, W. Y. Shan, S. Q. Shen, Q. Niu, X. L. Qi, S. C. Zhang, X. C. Ma, and Q. K. Xue, “Crossover of the threedimensional topological insulator Bi2Se3 to the two-dimensional limit,” Nat. Phys. 6, 584–588 (2010).

[28] C. C. Liu, W. Feng, and Y. Yao, “Quantum spin Hall effect in silicene and two-dimensional germanium,” Phys. Rev. Lett. 107, 076802 (2011).

[29] L. Li, Y. Yu, G. J. Ye, Q. Ge, X. Ou, H. Wu, D. Feng, X. H. Chen, and Y. Zhang, “Black phosphorus field-effect transistors,” Nat. Nanotechnol. 9, 372–377 (2014).

[30] J. Qiao, X. Kong, Z. X. Hu, F. Yang, and W. Ji, “High-mobility transport anisotropy and linear dichroism in few-layer black phosphorus,” Nat. Commun. 5, 4475 (2014).

[31] J. N. Coleman, M. Lotya, A. O’Neill, S. D. Bergin, P. J. King, U. Khan, K. Young, A. Gaucher, S. De, R. J. Smith, I. V. Schvets, S. K. Arora, G. Stanton, H. Kim, K. Lee, G. T. Kim, G. S. Duesberg, T. Hallam, J. J. Boland, J. J. Wang, J. F. Donegan, J. C. Grunlan, G. Moriarty, A. Shmeliov, R. J. Nicholls, J. M. Perkins, E. M. Grieveson, K. Theuwissen, D. W. McComb, P. D. Nellist, and V. Nicolosi, “Two-dimensional nanosheets produced by liquid exfoliation of layered materials,” Science 331, 568–571 (2011).

[32] Q. Bao, H. Zhang, Y. Wang, Z. Ni, Y. Yan, Z. Shen, K. Loh, and D. Tang, “Atomic-layer graphene as a saturable absorber for ultrafast pulsed lasers,” Adv. Funct. Mater. 19, 3077–3083 (2009).

[33] C. Zhao, H. Zhang, X. Qi, Y. Chen, Z. Wang, S. Wen, and D. Tang, “Ultra-short pulse generation by a topological insulator based saturable absorber,” Appl. Phys. Lett. 101, 211106 (2012).

[34] S. Wang, H. Yu, H. Zhang, A. Wang, M. Zhao, Y. Che, L. Mei, and J. Wang, “Broadband few-layer MoS2 saturable absorbers,” Adv. Mater. 26, 3538–3544 (2014).

[35] L. Ci, L. Song, C. Jin, D. Jariwala, D. Wu, Y. Li, A. Srivastava, Z. F. Wang, K. Storr, L. Balicas, F. Liu, and P. M. Ajayan, “Atomic layers of hybridized boron nitride and graphene domains,” Nat. Mater. 9, 430–435 (2010).

[36] S. Helveg, J. V. Lauritsen, E. L?gsgaard, I. Stensgaard, J. K. N?rskov, B. S. Clausen, H. Tops?e, and F. Besenbacher, “Atomic-scale structure of single-layer MoS2 nanoclusters,” Phys. Rev. Lett. 84, 951–954 (2000).

[37] S. Wu, J. S. Ross, G. B. Liu, G. Aivazian, A. Jones, Z. Fei, W. Zhu, D. Xiao, W. Yao, D. Cobden, and X. Xu, “Electrical tuning of valley magnetic moment through symmetry control in bilayer MoS2,” Nat. Phys. 9, 149–153 (2013).

[38] B. Radisavljevic, A. Radenovic, J. Brivio, V. Giacometti, and A. Kis, “Single-layer MoS2 transistors,” Nat. Nanotechnol. 6, 147–150 (2011).

[39] R. A. Gordon, D. Yang, E. D. Crozier, D. T. Jiang, and R. F. Frindt, “Structures of exfoliated single layers of WS2, MoS2, and MoSe2 in aqueous suspension,” Phys. Rev. B 65, 125407 (2002).

[40] H. S. S. Ramakrishna Matte, A. Gomathi, A. K. Manna, D. J. Late, R. Datta, S. K. Pati, and C. N. R. Ra, “MoS2 and WS2 analogues of graphene,” Angew. Chem. 122, 4153–4156 (2010).

[41] T. Li and G. Galli, “Electronic properties of MoS2 nanoparticles,” J. Phys. Chem. C 111, 16192–16196 (2007).

[42] K. K. Kam and B. A. Parkinson, “Detailed photocurrent spectroscopy of the semiconducting group VIB transition metal dichalcogenides,” J. Phys. Chem. 86, 463–467 (1982).

[43] A. Splendiani, L. Sun, Y. Zhang, T. Li, J. Kim, C. Y. Chim, G. Galli, and F. Wang, “Emerging photoluminescence in monolayer MoS2,” Nano Lett. 10, 1271–1275 (2010).

[44] R. Coehoorn, C. Haas, J. Dijkstra, C. J. F. Flipse, R. A. D. Groot, and A. Wold, “Electronic structure of MoSe2, MoS2, and WSe2. I. Band-structure calculations and photoelectron spectroscopy,” Phys. Rev. B 35, 6195–6202 (1987).

[45] J. S. Qi, X. Li, X. F. Qian, and J. Feng, “Bandgap engineering of rippled MoS2 monolayer under external electric field,” Appl. Phys. Lett. 102, 173112 (2013).

[46] H. J. Conley, B. Wang, J. I. Ziegler, R. F. Haglund, Jr., S. T. Pantelides, and K. I. Bolotin, “Bandgap engineering of strained monolayer and bilayer MoS2,” Nano Lett. 13, 3626–3630 (2013).

[47] A. Castellanos-Gomez, R. Roldán, E. Cappelluti, M. Buscema, F. Guinea, H. S. J. van der Zant, and G. A. Steele, “Local strain engineering in atomically thin MoS2,” Nano Lett. 13, 5361–5366 (2013).

[48] Q. H. Liu, L. Z. Y. F. Li, Z. X. Gao, Z. F. Chen, and J. Lu, “Tuning electronic structure of bilayer MoS2 by vertical electric field: A first-principles investigation,” J. Phys. Chem. C 116, 21556– 21562 (2012).

[49] Y. Kim, J. L. Huang, and C. M. Lieber, “Characterization of nanometer scale wear and oxidation of transition metal dichalcogenide lubricants by atomic force microscopy,” Appl. Phys. Lett. 59, 3404–3406 (1991).

[50] A. Carvalho, R. M. Ribeiro, and A. H. C. Neto, “Band nesting and the optical response of two-dimensional semiconducting transition metal dichalcogenides,” Phys. Rev. B 88, 115205 (2013).

[51] L. Britnell, R. M. Ribeiro, A. Eckmann, R. Jalil, B. D. Belle, A. Mishchenko, Y.-J. Kim, R. V. Gorbachev, T. Georgiou, S. V. Morozov, A. N. Grigorenko, A. K. Geim, C. Casiraghi, A. H. C. Neto, and K. S. Novoselov, “Strong light-matter interactions in heterostructures of atomically thin films,” Science 340, 1311–1314 (2013).

[52] R. Wang, B. A. Ruzicka, N. Kumar, M. Z. Bellus, H. Y. Chiu, and H. Zhao, “Ultrafast and spatially resolved studies of charge carriers in atomically thin molybdenum disulfide,” Phys. Rev. B 86, 045406 (2012).

[53] N. Kumar, S. Najmaei, Q. Cui, F. Ceballos, P. M. Ajayan, J. Lou, and H. Zhang, “Second harmonic microscopy of monolayer MoS2,” Phys. Rev. B 87, 161403 (2013).

[54] J. Strait, P. Nene, H. Wang, C. Zhang, and F. Rana, “Carrier relaxation dynamics in MoS2 measured by optical/THz pumpprobe spectroscopy,” in Conference on Lasers and Electro- Optics (CLEO), Technical Digest Series (OSA, 2013), paper JTh2A.37.

[55] H. Wang, C. Zhang, and F. Rana, “Ultrafast carrier dynamics in single and few layer MoS2 studied by optical pump probe technique,” in Conference on Lasers and Electro-Optics (CLEO), Technical Digest Series (OSA, 2013), paper QTu1D.2.

[56] K. Wang, J. Wang, J. Fan, M. Lotya, A. O’Neill, D. Fox, Y. Feng, X. Zhang, B. Jiang, Q. Zhao, H. Zhang, J. N. Coleman, L. Zhang, and W. J. Blau, “Ultrafast saturable absorption of two-dimensional MoS2 nanosheets,” ACS Nano 7, 9260–9267 (2013).

[57] O. Madelung, Introduction to Solid-State Theory, Vol. 2 (Springer, 1996), Chap. 8 and 9.

[58] G. Kresse and J. Furthmuller, “Efficiency of ab-initio total energy calculations for metals and semiconductors using a planewave basis set,” Comput. Mater. Sci. 6, 15–50 (1996).

[59] G. Kresse and J. Furthmüller, “Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set,” Phys. Rev. B 54, 11169–11186 (1996).

[60] V.Yu.Fominski,V. N.Nevolin, R. I.Romanov, and I.Smurov, “Ionassisted deposition of MoSx films from laser-generated plume under pulsed electric field,” J. Appl. Phys. 89, 1449–1457 (2001).

[61] E. Garmire and A. Kost, “Resonant optical nonlinearities in semiconductors,” in Nonlinear Optics in Semiconductor I, R. K. Willardson and E. R. Weber, eds. (Academic, 1999), pp. 2–50.

[62] E. Garmire, “Resonant optical nonlinearities in semiconductors,” IEEE J. Sel. Top. Quantum Electron. 6, 1094–1110 (2000).

[63] H. Yu, H. Zhang, Y. Wang, C. Zhao, B. Wang, S. Wen, H. Zhang, and J. Wang, “Topological insulator as an optical modulator for pulsed solid-state lasers,” Laser Photon. Rev. 7, L77–L83 (2013).

[64] W. D. Tan, C. Y. Su, R. J. Knize, G. Q. Xie, L. J. Li, and D. Tang, “Mode locking of ceramic Nd:yttrium aluminum garnet with graphene as a saturable absorber,” Appl. Phys. Lett. 96, 031106 (2010).

[65] J. Du, Q. Wang, G. Jiang, C. Xu, C. Zhao, Y. Xiang, Y. Chen, S. Wen, and H. Zhang, “Ytterbium-doped fiber laser passively mode locked by few-layer molybdenum disulfide (MoS2) saturable absorber functioned with evanescent field interaction,” Sci. Rep. 4, 6346 (2014).

[66] H. Zhang, S. B. Lu, J. Zheng, J. Du, S. C. Wen, D. Y. Tang, and K. P. Loh, “Molybdenum disulfide (MoS2) as a broadband saturable absorber for ultra-fast photonics,” Opt. Express 22, 7249–7260 (2014).

[67] H. Liu, A. Luo, F. Wang, R. Tang, M. Liu, Z. Luo, W. Xu, C. Zhao, and H. Zhang, “Femtosecond pulse erbium-doped fiber laser by a few-layer MoS2 saturable absorber,” Opt. Lett. 39, 4591–4594 (2014).

[68] M. Liu, X. W. Zheng, Y. L. Qi, H. Liu, A. Luo, Z. C. Luo, W. C. Xu, C. J. Zhao, and H. Zhang, “Microfiber-based few-layer MoS2 saturable absorber for 2.5 GHz passively harmonic modelocked fiber laser,” Opt. Express 22, 22841–22846 (2014).

[69] R. Khazaeizhad, S. H. Kassani, H. Jeong, D. I. Yeom, and K. Oh, “Mode-locking of Er-doped fiber laser using a multilayer MoS2 thin film as a saturable absorber in both anomalous and normal dispersion regimes,” Opt. Express 22, 23732–23742 (2014).

[70] Y. Z. Huang, Z. Q. Y. Y. Luo, Y. Y. Li, M. Zhong, B. Xu, K. J. Che, H. Y. Xu, Z. P. Cai, J. Peng, and J. Weng, “Widely-tunable, passively Q-switched erbium-doped fiber laser with few-layer MoS2 saturable absorber,” Opt. Express 22, 25258–25266 (2014).

[71] Z. Luo, Y. Huang, M. Zhong, Y. Li, J. Wu, B. Xu, H. Xu, Z. Cai, J. Peng, and J. Weng, “1, 1.5 and 2 μm fiber lasers Q-switched by a broadband few-layer MoS2 saturable absorber,” J. Lightwave Technol. 32, 4077–4084 (2014).

[72] J. Bardeen, L. N. Cooper, and J. R. Schrieffer, “Theory of superconductivity,” Phys. Rev. 108, 1175–1204 (1957).

[73] C. Haas, “Phase transitions in ferroelectric and antiferroelectric crystals,” Phys. Rev. 140, A863–A868 (1965).

[74] M. M. Qazilbash, M. Brehm, B.-G. Chae, P.-C. Ho, G. O. Andreev, B.-J. Kim, S. J. Yun, A. V. Balatsky, M. B. Maple, F. Keilmann, H.-T. Kim, and D. N. Basov, “Mott transition in VO2 revealed by infrared spectroscopy and nano-imaging,” Science 318, 1750–1753 (2007).

[75] N. B. Aetukuri, A. X. Gray, M. Drouard, M. Cossale, L. Gao, A. H. Reid, R. Kukreja, H. Ohldag, C. A. Jenkins, E. Arenholz, K. P. Roche, H. A. Dürr, M. G. Samant, and S. S. P. Parkin, “Control of the metal-insulator transition in vanadium dioxide by modifying orbital occupancy,” Nat. Phys. 9, 661–666 (2013).

[76] M. Nakano, K. Shibuya, D. Okuyama, T. Hatano, S. Ono, M. Kawasaki, Y. Iwasa, and Y. Tokura, “Collective bulk carrier delocalization driven by electrostatic surface charge accumulation,” Nature 487, 459–462 (2012).

[77] M. Liu, H. Y. Hwang, H. Tao, A. Strikwerda, K. Fan, G. R. Keiser, A. J. Sternbach, K. G. West, S. Kittiwatanakul, J. Lu, S. A. Wolf, F. G. Omenetto, X. Zhang, K. A. Nelson, and R. D. Averitt, “Terahertz- field-induced insulator-to-metal transition in vanadium dioxide metamaterial,” Nature 487, 345–348 (2012).

[78] V. Eyert, “VO2: A novel view from band theory,” Phys. Rev. Lett. 107, 016401 (2011).

[79] M. Imada, A. Fujimori, and Y. Tokura, “Metal–insulator transitions,” Rev. Mod. Phys. 70, 1039–1263 (1998).

[80] T. Yao, X. Zhang, Z. Sun, S. Liu, Y. Huang, Y. Xie, C. Wu, X. Yuan, W. Zhang, Z. Wu, G. Pan, F. Hu, L. Wu, Q. Liu, and S. Wei, “Understanding the nature of the kinetic process in a VO2 metal–insulator transition,” Phys. Rev. Lett. 105, 226405 (2010).

[81] J. Jeong, N. Aetukuri, T. Graf, T. D. Schladt, M. G. Samant, and S. S. P. Parkin, “Suppression of metal–insulator transition in VO2 by electric field-induced oxygen vacancy formation,” Science 339, 1402–1405 (2013).

[82] J. B. Goodenough, “Direct cation–cation interactions in several oxides,” Phys. Rev. 117, 1442–1451 (1960).

[83] T. C. Koethe, Z. Hu, M. W. Haverkort, C. Schü?ler-Langeheine, F. Venturini, N. B. Brookes, O. Tjernberg, W. Reichelt, H. H. Hsieh, H.-J. Lin, C. T. Chen, and L. H. Tjeng, “Transfer of spectral weight and symmetry across the metal-insulator transition in VO2,” Phys. Rev. Lett. 97, 116402 (2006).

[84] S. Biermann, A. Poteryaev, A. I. Lichtenstein, and A. Georges, “Dynamical singlets and correlation-assisted Peierls transition in VO2,” Phys. Rev. Lett. 94, 026404 (2005).

[85] A. Cavalleri, T. Dekorsy, H. H. W. Chong, J. C. Kiedder, and R. W. Schoenlein, “Evidence for a structurally-driven insulator-tometal transition in VO2: A view from the ultrafast timescale,” Phys. Rev. B 70, 161102 (2004).

[86] P. Limelette, A. Georges, D. Jérome, P. Wzietek, P. Metaclf, and J. M. Honig, “Universality and critical behavior at the Mott transition,” Science 302, 89–92 (2003).

[87] A. Cavalleri, C. Tóth, C. W. Siders, J. A. Squier, and F. Ráksi, “Femtosecond structural dynamics in VO2 during an ultrafast solid-solid phase transition,” Phys. Rev. Lett. 87, 237401 (2001).

[88] J. Umeda, H. Kusumoto, K. Narita, and E. Yamada, “Nuclear magnetic resonance in polycrystalline VO2,” J. Chem. Phys. 42, 1458–1459 (1965).

[89] J. H. Park, J. M. Coy, T. S. Kasirga, C. Huang, Z. Fei, S. Hunter, and D. H. Gobden, “Measurement of a solid-state triple point at the metal-insulator transition in VO2,” Nature 500, 431–434 (2013).

[90] H. Yu, S. Wang, A. Wang, M. Zhao, H. Zhang, Y. Chen, L. Mei, and J. Wang, “Kinetics of nonlinear optical response at insulator- metal transition in vanadium dioxide,” Adv. Opt. Mater. 3, 64–70 (2015)

[91] L. Wang, E. Radue, S. Kittiwatanakul, C. Clavero, J. Lu, S. A. Wolf, I. Novikova, and R. A. Lukaszew, “Surface plasmon polaritons in VO2 thin films for tunable low-loss plasmonic applications,” Opt. Lett. 37, 4335–4337 (2012).

[92] M. Rini, A. Cavalleri, R. W. Schoenlein, R. López, L. C. Feldman, R. F. Haglund, L. A. Boatner, and T. E. Haynes, “Photoinduced phase transition in VO2 nanocrystals: Ultrafast control of surface-plasmon resonance,” Opt. Lett. 30, 558–560 (2005).

[93] B. A. Kruger, A. Joushaghani, and J. K. S. Poon, “Design of electrically driven hybrid vanadium dioxide (VO2) plasmonic switches,” Opt. Express 20, 23598–23609 (2012).

[94] Y. Zhou, A. Huang, Y. Li, S. Ji, Y. Gao, and P. Jin, “Surface plasmon resonance induced excellent solar control for VO2@SiO2 nanorods-based thermochromic foils,” Nanoscale 5, 9208–9213 (2013).

[95] X. Zhang, S. Zhao, Q. Wang, Q. Zhang, L. Sun, and S. Zhang, “Optimization of Cr4+-doped saturable-absorber Q-switched lasers,” IEEE J. Quantum Electron. 33, 2286–2294 (1997).

[96] C. Kübler, H. Ehrke, R. Huber, R. Lopez, A. Halabica, R. F. Haglund, Jr., and A. Leitenstorfer, “Coherent structural dynamics and electronic correlations during an ultrafast insulator-to-metal phase transition in VO2,” Phys. Rev. Lett. 99, 116401 (2007).

[97] K. S. Novoselov, A. K. Geim, S. V. Morozov, D. Jiang, Y. Zhang, S. V. Dubonos, I. V. Grigorieva, and A. A. Firsov, “Electric field effect in atomically thin carbon films,” Science 306, 666–669 (2004).

[98] A. B. Kuzmenko, E. V. Heumen, F. Carbone, and D. V. D. Marel, “Universal optical conductance of graphite,” Phys. Rev. Lett. 100, 117401 (2008).

[99] R. R. Nair, P. Blake, A. N. Grigorenko, K. S. Novoselov, T. J. Booth, T. Stauber, N. M. R. Peres, and A. K. Geim, “Fine structure constant defines visual transparency of graphene,” Science 320, 1308 (2008).

[100] Z. Q. Li, E. A. Henriksen, Z. Jiang, Z. Hao, M. C. Martin, P. Kim, H. L. Stormer, and D. N. Basov, “Dirac charge dynamics in graphene by infrared spectroscopy,” Nat. Phys. 4, 532–535 (2008).

[101] J. M. Dawlaty, S. Shivaraman, M. Chandrashekhar, F. Rana, and M. G. Spencer, “Measurement of ultrafast carrier dynamics in epitaxial graphene,” Appl. Phys. Lett. 92, 042116 (2008).

[102] P. A. George, J. Strait, J. Dawlaty, S. Shivaraman, M. Chandrashekhar, F. Rana, and M. G. Spencer, “Ultrafast optical-pump terahertz-probe spectroscopy of the carrier relaxation and recombination dynamics in epitaxial graphene,” Nano Lett. 8, 4248–4251 (2008).

[103] M. Breusing, C. Ropers, and T. Elsaesser, “Ultrafast carrier dynamics in graphite,” Phys. Rev. Lett. 102, 086809 (2009).

[104] A. A. Balandin, S. Ghosh, W. Bao, I. Calizo, D. teweldebrhan, F. Miao, and C. N. Lau, “Superior thermal conductivity of single-layer graphene,” Nano Lett. 8, 902–907 (2008).

[105] S. V. Morozov, K. S. Novoselov, M. I. Katsnelson, F. Schedin, D. C. Elias, J. A. Jaszczak, and A. K. Geim, “Giant intrinsic carrier mobilities in graphene and its bilayer,” Phys. Rev. Lett. 100, 016602 (2008).

[106] C. Lee, X. Wei, J. W. Kysar, and J. Hone, “Measurement of the elastic properties and intrinsic strength of monolayer graphene,” Science 321, 385–388 (2008).

[107] H. Zhang, S. Virally, Q. Bao, K. P. Loh, S. Massar, N. Godbout, and P. Kockaert, “Z-scan measurement of the nonlinear refractive index of graphene,” Opt. Lett. 37, 1856–1858 (2012).

[108] Z. Luo, M. Zhou, J. Weng, G. M. Huang, H. Y. Xu, C. C. Ye, and Z. P. Cai, “Graphene-based passively Q-switched dual-wavelength erbium-doped fiber laser,” Opt. Lett. 35, 3709–3711 (2010).

[109] H. Yu, X. Chen, H. Zhang, X. Xu, X. Hu, Z. Wang, J. Wang, S. Zhuang, and M. Jiang, “Large energy pulse generation modulated by graphene epitaxially grown on silicon carbide,” ACS Nano 4, 7582–7586 (2010).

[110] H. Yu, X. Chen, X. Hu, S. Zhuang, Z. Wang, X. Xu, J. Wang, H. Zhang, and M. Jiang, “Graphene as a Q-switcher for neodymium- doped lutetium vanadate laser,” Appl. Phys. Express 4, 022704 (2011).

[111] Y. Ding, M. Xu, Y. Zhao, H. Yu, H. Zhang, Z. Wang, and J. Wang, “Thermally driven continuous-wave and pulsed optical vortex,” Opt. Lett. 39, 2366–2369 (2014).

[112] C. Z. Chang, J. Zhang, X. Feng, J. Shen, Z. Zhang, M. Guo, K. Li, Y. Ou, P. Wei, L. L. Wang, Z. Q. Ji, Y. Feng, S. Ji, X. Chen, J. Jia, X. Dai, Z. Fang, S. C. Zhang, K. He, Y. Wang, L. Lu, X. C. Ma, and Q. K. Xue, “Experimental observation of the quantum anomalous Hall effect in a magnetic topological insulator,” Science 340, 167–170 (2013).

[113] Y. L. Chen, J. G. Analytis, J. H. Chu, Z. K. Liu, S. K. Mo, X. L. Qi, H. J. Zhang, D. H. Lu, X. Dai, Z. Fang, S. C. Zhang, I. R. Fisher, Z. Hussain, and Z. X. Shen, “Experimental realization of a threedimensional topological insulator, Bi2Te3,” Science 325, 178– 181 (2009).

[114] H. Zhang, C. X. Liu, X. L. Qi, X. Dai, Z. Fang, and S. C. Zhang, “Topological insulators in Bi2Se3, Bi2 Te3 and Sb2Te3 with a single Dirac cone on the surface,” Nat. Phys. 5, 438–442 (2009).

[115] Y. Xia, D. Qian, D. Hsieh, L. Wray, A. Pal, H. Lin, A. Bansil, D. Grauer, Y. S. Hor, R. J. Cava, and M. Z. Hasan, “Observation of a large-gap topological-insulator class with a single Dirac cone on the surface,” Nat. Phys. 5, 398–402 (2009).

[116] J. E. Moore, “The birth of topological insulators,” Nature 464, 194–198 (2010).

[117] J. G. Analytis, R. D. McDonald, S. C. Riggs, J. H. Chu, G. S. Boebinger, and L. R. Fisher, “Two-dimensional surface state in the quantum limit of a topological insulator,” Nat. Phys. 6, 960–964 (2010).

[118] J. Moore, “Topological insulators: The next generation,” Nat. Phys. 5, 378–380 (2009).

[119] M. Veldhorst, M. Snelder, M. Hoek, T. Gang, V. K. Guduru, X. L. Wang, U. Zeitler, W. G. van der Wiel, A. A. Golubov, H. Hilgenkamp, and A. Brinkman, “Josephson supercurrent through a topological insulator surface state,” Nat. Mater. 11, 417–421 (2012).

[120] Y.L.Chen,J.H.Chu,J.G.Analytis,Z.K.Liu,K.Lgarashi,H.H.Kuo, S. K. Mo, R. G. Moore, D. H. Lu, M. Hashimoto, T. Sasagawa, S. C. Zhang, I. R. Fisher, Z. Hussain, and Z. X. Shen, “Massive Dirac fermion on the surface of a magnetically doped topological insulator,” Science 329, 659–662 (2010).

[121] F. Bernard, H. Zhang, S. P. Gorza, and P. Emplit, “Towards mode-locked fiber laser using topological insulators,” in Nonlinear Photonics, OSA Digest Series (OSA, 2012) paper NTh1A.5.

[122] B. Wang, H. Yu, H. Zhang, C. Zhao, S. Wen, H. Zhang, and J. Wang, “Topological insulator simultaneously Q-switched dual-wavelength Nd:Lu2O3 laser,” IEEE J. Photon. 6, 1501007 (2014).

[123] Z. Luo, Y. Huang, J. Weng, H. Cheng, Z. Lin, B. Xu, Z. Cai, and H. Xu, “1.06 μm Q-switched ytterbium-doped fiber laser using few-layer topological insulator Bi2Se3 as a saturable absorber,” Opt. Express 21, 29516–29522 (2013).

[124] C. Zhao, Y. Zou, Y. Chen, Z. Wang, S. Lu, H. Zhang, S. Wen, and D. Tang, “Wavelength-tunable picosecond soliton fiber laser with topological insulator: Bi2Se3 as a mode locker,” Opt. Express 20, 27888–27895 (2012).

[125] Y. Chen, C. Zhao, H. Huang, S. Chen, P. Tang, Z. Wang, S. Lu, H. Zhang, S. Wen, and D. Tang, “Self-assembled topological insulator: Bi2Se3 membrane as a passive Q-switcher in an erbium– doped fiber laser,” J. Lightwave Technol. 31, 2857–2863 (2013).

[126] Z. C. Luo, M. Liu, H. Liu, X. W. Zheng, A. P. Luo, C. J. Zhao, H. Zhang, S. C. Wen, and W. C. Xu, “2 GHz passively harmonic mode-locked fiber laser by a microfiber-based topological insulator saturable absorber,” Opt. Lett. 38, 5212–5215 (2013).

[127] P. Tang, X. Zhang, C. Zhao, Y. Wang, H. Zhang, D. Shen, S. Wen, D. Tang, and D. Fan, “Topological insulator: Bi2Te3 saturable absorber for the passive Q-switching operation of an in-band pumped 1645-nm Er:YAG ceramic laser,” IEEE J. Photon. 5, 1500707 (2013).

[128] M. Jung, J. Lee, J. Koo, J. Park, Y. W. Song, K. Lee, S. Lee, and J. H. Lee, “A femtosecond pulse fiber laser at 1935 nm using a bulk-structured Bi2Te3 topological insulator,” Opt. Express 22, 7865–7874 (2014).

[129] Z. Q. Luo, C. Liu, Y. Z. Huang, D. D. Wu, J. Y. Wu, H. Y. Xu, Z. P. Cai, Z. Q. Lin, L. P. Sun, and J. Weng, “Topological-insulator passively Q-switched double-clad fiber laser at 2 μm wavelength,” IEEE J. Sel. Top. Quantum Electron. 20, 0902708 (2014).