Saturable Absorption in 2D Ti3 C2 MXene Thin Films for Passive Photonic Diodes

Yongchang Dong; Sergii Chertopalov; Kathleen Maleski; Babak Anasori; Longyu Hu; Sriparna Bhattacharya; Apparao M Rao; Yury Gogotsi; Vadym N Mochalin; Ramakrishna Podila

doi:10.1002/adma.201705714

Saturable Absorption in 2D Ti₃ C₂ MXene Thin Films for Passive Photonic Diodes

Adv Mater. 2018 Mar;30(10). doi: 10.1002/adma.201705714. Epub 2018 Jan 15.

Authors

Affiliations

¹ Department of Physics and Astronomy and Clemson Nanomaterials Institute, Clemson University, Clemson, SC, 29634, USA.
² Department of Chemistry, Missouri University of Science and Technology, Rolla, MO, 65409, USA.
³ Department of Materials Science and Engineering and A.J. Drexel Nanomaterials Institute, Drexel University, Philadelphia, PA, 19104, USA.
⁴ Materials Science and Engineering and A.J. Drexel Nanomaterials Institute, Drexel University, Philadelphia, PA, 19104, USA.
⁵ Department of Materials Science and Engineering, Missouri University of Science and Technology, Rolla, MO, 65409, USA.

PMID: 29333627
DOI: 10.1002/adma.201705714

Abstract

MXenes comprise a new class of 2D transition metal carbides, nitrides, and carbonitrides that exhibit unique light-matter interactions. Recently, 2D Ti₃ CNT_x (T_x represents functional groups such as OH and F) was found to exhibit nonlinear saturable absorption (SA) or increased transmittance at higher light fluences, which is useful for mode locking in fiber-based femtosecond lasers. However, the fundamental origin and thickness dependence of SA behavior in MXenes remain to be understood. 2D Ti₃ C₂ T_x thin films of different thicknesses are fabricated using an interfacial film formation technique to systematically study their nonlinear optical properties. Using the open aperture Z-scan method, it is found that the SA behavior in Ti₃ C₂ T_x MXene arises from plasmon-induced increase in the ground state absorption at photon energies above the threshold for free carrier oscillations. The saturation fluence and modulation depth of Ti₃ C₂ T_x MXene is observed to be dependent on the film thickness. Unlike other 2D materials, Ti₃ C₂ T_x is found to show higher threshold for light-induced damage with up to 50% increase in nonlinear transmittance. Lastly, building on the SA behavior of Ti₃ C₂ T_x MXenes, a Ti₃ C₂ T_x MXene-based photonic diode that breaks time-reversal symmetry to achieve nonreciprocal transmission of nanosecond laser pulses is demonstrated.

Keywords: 2D materials; MXenes; nonlinear optics; optical diodes; thin films; titanium carbide.