Giant and Tunable Optical Nonlinearity via <i>In Situ</i> Electrochemical Control of the Tellurium-Electrolyte Interface.
basic_science · Level V
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- Record sourced from PubMed, PMID 40916197.
- Also identified by DOI 10.1021/acs.nanolett.5c04042.
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Abstract
The semiconductor-electrolyte interface with strong electrical tunability offers a platform for tuning nonlinear optical (NLO) processes and achieving giant optical nonlinearities. However, such a demonstration and fundamental mechanistic understanding of electrochemically tuned NLO properties have not been reported. Here, we developed an <i>in situ</i> electrochemical Z-scan system to characterize the evolution of NLO responses in tellurium nanorod films under bias voltage. Nonlinear absorption (<i>β</i>) and refraction (<i>n</i><sub>2</sub>) indexes change from -6575 cm/GW and -0.238 cm<sup>2</sup>/GW at -0.3 V to -12500 cm/GW and -0.390 cm<sup>2</sup>/GW at 0.3 V, displaying diode-like rectification characteristics. Macroscopically, this tunable third-order nonlinear susceptibility (<i>χ̃</i><sup>(3)</sup>) mainly arises from the contribution of fourth-order nonlinear susceptibility (<i>χ̃</i><sup>(4)</sup><b><i>E</i></b>) under an electric field. Microscopically, the voltage-controlled band bending modulates carrier density, absorption cross-section, and relaxation time, thereby tuning nonlinear absorption and refraction. Our work demonstrates an electrochemical tuning strategy that enables giant and broadly tunable optical nonlinearity in nanomaterial systems.