中文 |

Research Progress

Researchers Demonstrate Slow and Fast Absorption Saturation of Black Phosphorus

Nov 24, 2016

As an emerging two-dimensional layered material, black phosphorus (BP) has shown superior optical features (saturable absorption (SA) performance) over its counterparts like the family of transition metal dichalcogenides (MoS2, WS2, etc.) and graphene. It has been widely used as a superior saturable absorber in Q-switching and mode-locking. However, the reason why the saturable intensity of BP is much lower than graphene is still to be explored. 

Scientists have demonstrated that excited-state absorption (ESA) exists in BP nanosheets using a two color pump–probe spectroscopy technique, which implies that the ESA and ground-state absorption (GSA) may play an important role in the nonlinear absorption process of BP and need to be taken into account. 

Researchers at Shanghai Institute of Optics and Fines Mechanics (SIOM) of Chinese Academy of Sciences (CAS) found that for BP, the critical parameter of saturable material is the smallest through experiments. They demonstrated that the ground-state transition probability of BP is relatively large and the excited-state transition probability is small, which results in good state-filling in the momentum space of the conduction band due to the Pauli Exclusion Principle. The findings can explain well the superior saturable absorption property of BP in the visible (VIS) to near-infrared (NIR) range. 

During the experiments, researchers have obtained the GSA and ESA cross sections σgs and σes of BP nanosheets, (1.25 ± 0.07) × 10−16 cm2 and (2.97 ± 0.21) × 10−17 cm2 at 515 nm, and (5.95 ± 0.17) ×10−18 cm2 and (5.19 ± 0.71) × 10−19 cm2 at 1030 nm with the slow SA model. The ratio of σesgs is about 0.24 ± 0.03 at 515 nm and 0.09 ± 0.01 at 1030 nm. It is even lower when the fast SA model is applied. The σgs and σes of MoS2 and graphene were also achieved using the slow SA model. It is clear that the ratio σesgs of BP is the smallest among the three two-dimensional layered materials. 

The results fundamentally support that BP can be used as a saturable absorber in nanophotonic devices. The study was published in Nanoscale. 

This work was supported by National Natural Science Foundation of China, the External Cooperation Program of CAS, the Key Research Program of Frontier Science of CAS, and the Strategic Priority Research Program of CAS, etc. 

Contact Us
  • 86-10-68597521 (day)

    86-10-68597289 (night)

  • 86-10-68511095 (day)

    86-10-68512458 (night)

  • cas_en@cas.cn

  • 52 Sanlihe Rd., Xicheng District,

    Beijing, China (100864)

Copyright © 2002 - Chinese Academy of Sciences