volume | PIER Journals

Abstract

All-optical nonlinear modulators, capable of femtosecond-scale signal modulation, are pivotal for high-speed data transmission in next-generation space optical communications. However, the inherently weak third-order optical nonlinearity of conventional materials remains a significant bottleneck for efficient nonlinear signal processing. In this work, we unveil the extraordinary third-order nonlinear susceptibility χ⁽³⁾ of atomically thin two-dimensional (2D) indium tin oxide (ITO) films within the 1550-nm telecommunications band. By leveraging quantum confinement effects, these 2D ITO layers form discrete electronic subbands that dramatically enhance intersubband transition dipole moments and thus the optical responses. Experimental measurements reveal a record-high angle-averaged χ⁽³⁾ value of 2.0 × 10^-(14) m²/V², representing an approximately 300-fold enhancement over bulk ITO and surpassing graphene by a factor of five. Furthermore, the 2D ITO films maintain high transparency and possess the potential for ultrafast response speeds inherent to electronic nonlinear processes, making them ideal candidates for compact nonlinear photonic integration. These findings demonstrate that 2D ITO, as a representative example of bandgap-engineered transparent conductive oxides (TCOs), provides a versatile platform for high-performance all-optical switching and signal processing in optical networks.

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Dr. Zhuoer Chen

Dr. Yiyun Zhang

Dr. Junru Niu

Dr. Lian Shen

Dr. Yeon Ui Lee

Professor Hongsheng Chen

Dr. Bingtao Gao

Professor Shilong Li