Chongfan Technology
News
18
2026
-
05
The Shanghai Institute of Optics and Fine Mechanics has made progress in studying the nonlinear optical properties and ultrafast carrier dynamics of In₂Se₃.
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Recently, the research team led by Researcher Jun Wang at the Department of Frontier Interdisciplinary Photonics of the Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, has made significant progress in the nonlinear optical properties and ultrafast carrier dynamics of layered In2Se3 nanosheets. The relevant findings, titled “Tunable Nonlinear Optical Properties and Ultrafast Dynamics in 2D α-In?Se? via Thickness Control,” were published in Optics & Laser Technology.
α‑In₂Se₃, with its direct bandgap, high carrier mobility, room‑temperature ferroelectricity, and broadband optical response, holds great promise for nanophotonic and optoelectronic devices. Its bandgap exhibits a strong thickness dependence, allowing precise tuning of the photon‑energy response window simply by adjusting the number of layers, thereby offering unique design flexibility for high‑performance, customizable photodetectors. However, nonlinear optical studies of this material are still in their infancy, and the underlying mechanisms governing its thickness‑dependent nonlinear optical properties and ultrafast carrier dynamics remain unclear. Systematically investigating the intrinsic relationship between α‑In₂Se₃’s layer thickness, its nonlinear optical response, and its carrier relaxation processes will not only shed light on novel physical mechanisms of light–matter interactions in low‑dimensional semiconductors but also lay a critical theoretical and experimental foundation for advancing its applications in ultrafast photonics, broadband optical modulation, and nonlinear optoelectronic devices.
The research team obtained high‑quality 2H‑phase α‑In₂Se₃ nanosheets via mechanical exfoliation and investigated their steady‑state and transient optical properties as a function of thickness. As the thickness decreases, the optical bandgap continuously widens from 1.57 eV to 2.13 eV, providing direct evidence of quantum confinement effects. Measurements based on micro‑area Z‑scan, I‑scan, and ultrafast pump–probe spectroscopy further reveal that both the material’s nonlinear absorption coefficient and the carrier relaxation lifetime exhibit pronounced variations with thickness. Specifically, carrier relaxation follows a biexponential decay, corresponding to the capture processes associated with shallow and deep defect levels, respectively; the lifetimes of both processes increase as the thickness diminishes. This behavior arises from the upward shift of the conduction band minimum induced by quantum confinement, which raises the energy barrier for carrier trapping by intrinsic defects such as selenium vacancies, thereby reducing the trapping rate. This work demonstrates that thickness engineering enables effective tuning of the two‑dimensional In₂Se₃’s nonlinear optical properties and carrier dynamics, laying a crucial physical foundation for its applications in programmable nonlinear photonic devices and high‑performance photodetectors.
This research was supported by the National Key R&D Program (2024YFA1409400).
Figure 1. Optical absorption, nonlinear optical properties, and carrier dynamics of two-dimensional α-In₂Se₃. (a) Optical bandgap characterization of α-In₂Se₃ with varying thickness; (b) Thickness dependence of the nonlinear absorption coefficient and saturation intensity; (c–d) Transient absorption spectra of In₂Se₃ at different thicknesses.
Source: Shanghai Institute of Optics and Fine Mechanics
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