Completely Anisotropic Ultrafast Optical Switching and Direction-Dependent Photocarrier Diffusion in Layered ZrTe5

Sung Bok Seo, Sanghee Nah, Muhammad Sajjad, Jiacheng Song, Nirpendra Singh, Sang Ho Suk, Hionsuck Baik, Sanghoon Kim, Geun Ju Kim, Jung Il Kim, Sangwan Sim

Research output: Contribution to journalArticlepeer-review

7 Scopus citations

Abstract

Layered nanomaterials with in-plane anisotropy exhibit unique orientation-dependent responses to external stimuli, enabling the development of novel devices with additional degrees of freedom. In particular, their anisotropic optical properties enable ultrafast nanophotonic modulators to be controlled by light polarization. However, achieving high controllability is still challenging due to incomplete optical anisotropy in most materials. Here, this work presents a completely anisotropic, ultrafast optical modulation in zirconium pentatelluride (ZrTe5), a layered nanomaterial that has recently attracted renewed attention. The transient absorption (TA) microscopy reveals anisotropic ultrafast picosecond optical modulation in a broad range of 1.2–2.2 eV. In particular, at a certain photon-energy of 1.62 eV, complete on/off switching with a near-unity degree of anisotropy is achieved solely by changing the light polarization, suggesting that ZrTe5 is a promising material for polarization-selective high-speed optical modulators. The theoretical analysis of the transition dipole moments attributes this sharp anisotropy to strongly polarization-dependent excited-state absorption. Furthermore, this work directly observes direction-dependent photocarrier transport using scanning TA microscopy. It yields the anisotropic diffusivity, mobility, and diffusion lengths of the photocarriers, which are essential parameters for designing devices. Therefore, this work provides a comprehensive understanding of the anisotropic optical characteristics of ZrTe5 on ultrafast timescales.

Original languageBritish English
Article number2201544
JournalAdvanced Optical Materials
Volume11
Issue number3
DOIs
StatePublished - 3 Feb 2023

Keywords

  • anisotropic layered materials
  • anisotropic polarization dependence
  • photocarrier diffusion
  • ultrafast optical modulation
  • zirconium pentatelluride

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