Sub-picosecond, strain-tunable, polarization-selective optical switching via anisotropic exciton dynamics in quasi-1D ZrSe3

• Published in: Light, science & applications science & applications, 2024-09, Vol.13 (1), p.240-13, Article 240
• Main Authors: Suk, Sang Ho, Nah, Sanghee, Sajjad, Muhammad, Seo, Sung Bok, Chen, Jianxiang, Sim, Sangwan
• Format: Article
• Language: English
• Subjects: 140/125; 639/624/400/584; 639/766/400/1021; 639/766/400/584; Anisotropy; Electrons; Energy; Lasers; Light; Microscopy; Microwaves; Nanomaterials; Optical and Electronic Materials; Optical Devices; Optical properties; Optics; Photonics; Physics; Physics and Astronomy; Polarization; Polarized light; RF and Optical Engineering
• ISSN: 2047-7538; 2047-7538
• DOI: 10.1038/s41377-024-01585-0

In cutting-edge optical technologies, polarization is a key for encoding and transmitting vast information, highlighting the importance of selectively switching and modulating polarized light. Recently, anisotropic two-dimensional materials have emerged for ultrafast switching of polarization-multiplexed optical signals, but face challenges with low polarization ratios and limited spectral ranges. Here, we apply strain to quasi-one-dimensional layered ZrSe 3 to enhance polarization selectivity and tune operational energies in ultrafast all-optical switching. Initially, transient absorption on unstrained ZrSe 3 reveals a sub-picosecond switching response in polarization along a specific crystal axis, attributed to shifting-recovery dynamics of an anisotropic exciton. However, its polarization selectivity is weakened by a slow non-excitonic response in the perpendicular polarization. To overcome this limitation, we apply strain to ZrSe 3 by bending its flexible substrate. The compressive strain spectrally decouples the excitonic and non-excitonic components, doubling the polarization selectivity of the sub-picosecond switching and tripling it compared to that in the tensile-strained ZrSe 3 . It also effectively tunes the switching energy at a shift rate of ~93 meV % -1 . This strain-tunable switching is repeatable, reversible, and robustly maintains the sub-picosecond operation. First-principles calculations reveal that the strain control is enabled by momentum- and band-dependent modulations of the electronic band structure, causing opposite shifts in the excitonic and non-excitonic transitions. Our findings offer a novel approach for high-performance, wavelength-tunable, polarization-selective ultrafast optical switching. Strain control of quasi-1D ZrSe 3 enables ultrafast, polarization-selective optical switching with enhanced selectivity and tunable switching energies.