Ultrafast Nonlinear Optical Excitation Behaviors of Mono- and Few-Layer Two Dimensional MoS₂

Abstract

The layered MoS₂ has recently attracted significant attention for its excellent nonlinear optical properties. Here, the ultrafast nonlinear optical (NLO) absorption and excited carrier dynamics of layered MoS₂ (monolayer, 3–4 layers, and 6–8 layers) are investigated via Z-scan and transient absorption spectra. Our experimental results reveal that NLO absorption coefficients of these MoS₂ increase from–27 × 10³ cm/GW to–11 × 10³ cm/GW with more layers at 400-nm laser excitation, while the values decrease from 2.0 × 10³ cm/GW to 0.8 × 10³ cm/GW at 800 nm. In addition, at high pump fluence, when the NLO response occurs, the results show that not only the reformation of the excitonic bands, but also the recovery time of NLO response decreases from 150 ps to 100 ps with an increasing number of layers, while the reductive energy of A excitonic band decreases from 191.7 meV to 51.1 meV. The intriguing NLO response of MoS₂ provides excellent potentials for the next-generation optoelectronic and photonic devices.

Keywords

Ultrafast optics / two-dimensional materials / ultrafast photonic devices

References

[1] Mak K. F., He K., Lee C., Lee G. H., Hone J., Heinz T. F., . Tightly bound trions in monolayer MoS₂. Nature Materials, 2013, 12(3): 207-211.

[2] Tsai D. S., Liu K. K., Lien D. H., Tsai M. L., Kang C. F., Lin C. A., . Few-layer MoS₂ with high broadband photogain and fast optical switching for use in harsh environment. ACS Nano, 2013, 7(5): 3905-3911.

[3] Wang K. P., Wang J., Fan J. T., Lotya M., O’Neill A., Fox D., . Ultrafast saturable absorption of two-dimensional MoS₂ nanosheets. ACS Nano, 2013, 7(10): 9260-9267.

[4] Zheng X., Chen R. Z., Shi G., Zhang J. W., Xu Z. J., Cheng X. A., . Characterization of nonlinear properties of black phosphorus nanoplatelets with femtosecond pulsed Z-scan measurements. Optics Letters, 2015, 40, 3480-3483.

[5] Jiang Y. Q., Miao L. L., Jiang G. B., Chen Y., Qi X., Jiang X. F., . Broadband and enhanced nonlinear optical response of MoS₂/graphene nanocomposites for ultrafast photonics applications. Scientific Reports, 2015, 5, 16372-1–16372–12.

[6] Huang Z. Y., Han W. J., Tang H. L., Ren L., Chander D. S., Qi X., . Photoelectrochemical-type sunlight photodetector based on MoS₂/graphene heterostructure. 2D Materials, 2015, 2(3): 035011-1–035011–6.

[7] Dhanabalan S. C., Ponraj J. S., Bao Q., Zhang H.. Present perspectives of broadband photo-detectors based on nanobelts, nanoribbons, nanosheets and the emerging 2D materials. Nanoscale, 2016, 8, 6410-6434.

[8] Liu M., Zheng X. M., Qi Y. L., Liu H., Luo A. P., Luo Z. C., . Microfiber-based few-layer MoS₂ saturable absorber for 2.5 GHz passively harmonic mode-locked fiber laser. Optics Express, 2014, 22(19): 22841-22846.

[9] Ponraj J. S., Xu Z. Q., Dhanabalan S. C., Mu H., Wang Y., Yuan J., . Photonics and optoelectronics of two-dimensional materials beyond graphene. Nanotechnology, 2016, 27, 462001-1–462001–33.

[10] Mao D., Wang Y. D., Ma C. J., Han L., Jiang B. Q., Gan X. T., . WS₂ mode-locked ultrafast fiber laser. Scientific Reports, 2015, 5(7965): 7965-1–7965–7.

[11] Zhang S. F., Dong N. N., Mcevoy N., O’Brien M., Winters S., Berner N. C., . Direct observation of degenerate two-photon absorption and its saturation in WS₂ and MoS₂ monolayer and few-layer films. ACS Nano, 2015, 9, 7142-7150.

[12] Mak K. F., Lee C., Hone J., Shan J., Heinz T. F.. Atomically thin MoS₂: a new direct-gap semiconductor. Physical Review Letters, 2010, 105, 136805-1–136805–15.

[13] Wang H., Zhang C., Rana F.. Ultrafast dynamics of defect-assisted electron-hole recombination in monolayer MoS₂. Nano Letters, 2015, 15(1): 339-345.

[14] Nie Z., Long R., Teguh J. S., Huang C. C., Hewak D. W., Yeow E. K. L., . Ultrafast electron and hole relaxation pathways in few-layer MoS₂. Journal of Physical Chemistry C, 2015, 119, 20698-20708.

[15] Moody G., Schaibley J., Xu X.. Exciton dynamics in monolayer transition metal dichalcogenides. Journal of the Optical Society of America B, 2016, 33(7): C39-C49.

[16] Shi H., Yan R., Bertolazzi S., Brivio J., Gao B., Kis A., . Exciton dynamics in suspended monolayer and few-layer MoS₂ 2D crystals. ACS Nano, 2013, 7(2): 1072-1080.

[17] Tsokkou D., Yu X., Sivula K., Banerji N.. The role of excitons and free charges in the excited-state dynamics of solution-processed few-layer MoS₂ nanoflakes. Journal of Physical Chemistry C, 2016, 120(40): 23286-23292.

[18] Yu Y. F., Li C., Liu Y., Su L. Q., Zhang Y., Cao L. Y.. Controlled scalable synthesis of uniform, high-quality monolayer and few-layer MoS₂ films. Scientific Reports, 2013, 3(5): 01866-1–01866–6.

[19] Ataca C., Şahin H., Ciraci S.. Stable, single-layer MX₂ transition-metal oxides and dichalcogenides in a honeycomb-like structure. Journal of Physical Chemistry C, 2012, 116, 8983-8999.

[20] Li H., Zhang Q., Yap C. C. R., Tay B. K., Edwin T. H. T., Olivier A., . From bulk to monolayer MoS₂: evolution of Raman scattering. Advanced Functional Materials, 2012, 22(7): 1385-1390.

[21] Splendiani A., Sun L., Zhang Y., Li T., Kim J., Chim C. Y., . Emerging photoluminescence in monolayer MoS₂. Nano Letters, 2010, 10(4): 1271-1275.

[22] Ramasubramaniam A.. Large excitonic effects in monolayers of molybdenum and tungsten dichalcogenides. Physical Review B Condensed Matter, 2012, 86(11): 2757-2764.

[23] Jiang T., Chen R. Z., Zheng X., Xu Z. J., Tang Y. H.. Photo-induced excitonic structure renormalization and broadband absorption in monolayer tungsten disulphide. Optics Express, 2018, 26(2): 859-869.