Recent research works on single-walled carbon nanotube (SWCNT) based material has witnessed a great technological importance in photonic applications due to their unique optical characteristics. Present work aims to employ theoretical first principles study to explore the electronic and optical properties of SWCNT in the form of armchair nanotube. The theoretical simulation is done by using density functional theory (DFT) as implemented in the CASTEP computer code. Similar to almost gapless nature of graphene, formation of Fermi level of a relaxed SWCNT structure is found to be at a value approaching zero. The calculated electronic band structure shows a direct band gap of 0.259 eV with Dirac cone form between conduction and valence band. The optical spectrum shows a variation of real and imaginary of dielectric function with inter-band transition taking place along with frequency of the incident light. The absorption spectrum exhibits a significant degree of anisotropic characteristic with almost transparent nature ranging from near infrared to ultraviolet energy range. These optical spectra show excellent nonlinear optical features which remark the suitability in optoelectronic applications.

Research on hybrid graphene with other two-dimensional materials has gained considerable attention owing to their potential applications beyond single components. Through our first principles analysis via density functional theory, graphene-molybdenum disulphide (MoS2) demonstrated a band gap opening by 2 meV, from gapless graphene when MoS2 layer is introduced into the structure. The simulated graphene-MoS2 has a direct band gap situated at K point of Brillouin zone with preserved Dirac properties of graphene. The experimental studies on graphene-MoS2 also have been performed by preparing graphene-MoS2-chitin nanocomposite through facile liquid-phase exfoliation method. Apart from energy gap using Tauc relation, the physical morphology and nonlinear properties of the material were systematically characterized. Graphene-MoS2-chitin exhibits a modulation depth of 10.5%, which is lower than individual graphene but higher than individual MoS2. Further investigation on the material’s performance was done by integrating the fabricated film into Erbium-doped fiber laser. Stable nanosecond pulse laser operation was realized with graphene-MoS2-chitin hybrid saturable absorber. The pulse width was measured to be 156.4 ns with repetition rate of 1.89 MHz, corresponding to a peak power of 56.13 mW and pulse energy of 8.78 nJ.

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A simple fabrication of graphene-MoS2 nanocomposite, as well as individual graphene and molybdenum disulphide (MoS2) film has been done through a liquid phase exfoliation method using chitin as a binder. All of the developed films are integrated as a passive Q-switcher in an Erbium doped fiber laser. The graphene-MoS2 nanocomposite based passive Q-switcher is generated by a pulsed fiber laser with the shortest width of 1.63 µs and the highest signal to noise ratio of 51.01 dB. The graphene-MoS2 nanocomposite films show a better saturable absorption response compared to an individual graphene-chitin and MoS2-chitin based passive Q-switcher. Full Text: PDF ReferencesB. Zhang et al., "Recent Progress in 2D Material-Based Saturable Absorbers for All Solid-State Pulsed Bulk Lasers", Laser Photon. Rev. 14(2), 1900240 (2020). CrossRef M. Zhang, H. Chen, J. Yin, J. Wang, P. Yan, "Recent development of saturable absorbers for ultrafast lasers [Invited]", Chinese Opt. Letters 19(8), 081405 (2021). CrossRef S.A. Hussain, "Beta rhythm events predict corticospinal motor output", Scientific Reports 9(1), 1 (2019). CrossRef B. Fu, Y. Hua, X. Xiao, H. Zhu, Z. Sun, C. Yang, "Broadband Graphene Saturable Absorber for Pulsed Fiber Lasers at 1, 1.5, and 2 μm", IEEE J. Selected Topics in Quant. Electron. 20(5), 411 (2014). CrossRef S.N.M. Halim, S.N.F. Zuikafly, M.F.M. Taib, F. Ahmad, "First Principles Study on Electronic and Optical Properties of Graphene/MoS2 for Optoelectronic Application", IEEE International Conference on Semiconductor Electronics (ICSE), 29-32, (2020), CrossRef Z. Wang, H. Mu, J. Yuan, C. Zhao, Q. Bao, H. Zhang, "Graphene-Bi2Te3 Heterostructure as Broadband Saturable Absorber for Ultra-Short Pulse Generation in Er-Doped and Yb-Doped Fiber Lasers", Quant. Electron. 23(1), 195 (2016). CrossRef E.P. Randviir, D.A. Brownson, C.E. Banks, "A decade of graphene research: production, applications and outlook", Materials Today 17(9), 426 (2014). CrossRef S.N.F. Zuikafly, N.F. Razak, R.M. Rosnan, S.W. Harun, F. Ahmad, "Graphene slurry based passive Q-switcher in erbium doped fiber laser", Bull. Electr. Engin. Informat. 8(4), 1351 (2019). CrossRef W.M.F.W. Nawawi, K.-Y. Lee, E. Kontturi, R.J. Murphy, A. Bismarck, "Chitin Nanopaper from Mushroom Extract: Natural Composite of Nanofibers and Glucan from a Single Biobased Source", ACS Sustainable Chem. Engin. 7(7), 6492 (2019). CrossRef