Quantum-Enhanced Tunable Second-Order Optical Nonlinearity in Bilayer Graphene

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• 作者：Sanfeng Wu ; Li Mao ; Aaron M. Jones ; Wang Yao ; Chuanwei Zhang ; Xiaodong Xu
• 刊名：Nano Letters
• 出版年：2012
• 出版时间：April 11, 2012
• 年：2012
• 卷：12
• 期：4
• 页码：2032-2036
• 全文大小：323K
• 年卷期：v.12,no.4(April 11, 2012)
• ISSN：1530-6992

文摘

Second order optical nonlinear processes involve the coherent mixing of two electromagnetic waves to generate a new optical frequency, which plays a central role in a variety of applications, such as ultrafast laser systems, rectifiers, modulators, and optical imaging. However, progress is limited in the mid-infrared (MIR) region due to the lack of suitable nonlinear materials. It is desirable to develop a robust system with a strong, electrically tunable second order optical nonlinearity. Here, we demonstrate theoretically that AB-stacked bilayer graphene (BLG) can exhibit a giant and tunable second order nonlinear susceptibility 蠂⁽²⁾ once an in-plane electric field is applied. 蠂⁽²⁾ can be electrically tuned from 0 to 10⁵ pm/V, 3 orders of magnitude larger than the widely used nonlinear crystal AgGaSe₂. We show that the unusually large 蠂⁽²⁾ arise from two different quantum enhanced two-photon processes thanks to the unique electronic spectrum of BLG. The tunable electronic bandgap of BLG adds additional tunability on the resonance of 蠂⁽²⁾, which corresponds to a tunable wavelength ranging from 2.6 to 3.1 渭m for the up-converted photon. Combined with the high electron mobility and optical transparency of the atomically thin BLG, our scheme suggests a new regime of nonlinear photonics based on BLG.

Keywords:

Bilayer graphene; second harmonic generation; double resonance enhancement; perturbation theory; tunability; polarization