Rossetti Andrea, Hu Huatian, Venanzi Tommaso, Bousseksou Adel, De Luca Federico, Deckert Thomas, Giliberti Valeria, Pea Marialilia, Sagnes Isabelle, Beaudoin Gregoire, Biagioni Paolo, Baù Enrico, Maier Stefan A, Tittl Andreas, Brida Daniele, Colombelli Raffaele, Ortolani Michele, Ciracì Cristian
Department of Physics and Materials Science, University of Luxembourg, 162a avenue de la Faïencerie, Luxembourg, L-1511, Luxembourg.
Center for Biomolecular Nanotechnologies, Istituto Italiano di Tecnologia, via Barsanti 14, Arnesano, 73010, Italy.
Light Sci Appl. 2025 May 13;14(1):192. doi: 10.1038/s41377-025-01783-4.
The efficiency of nanoscale nonlinear elements in photonic integrated circuits is hindered by the physical limits to the nonlinear optical response of dielectrics, which cannot be engineered as it is a fundamental material property. Here, we experimentally demonstrate that ultrafast optical nonlinearities in doped semiconductors can be engineered and can easily exceed those of conventional undoped dielectrics. The electron response of heavily doped semiconductors acquires in fact a hydrodynamic character that introduces nonlocal effects as well as additional nonlinear sources. Our experimental findings are supported by a comprehensive computational analysis based on the hydrodynamic model. In particular, by studying third-harmonic generation from plasmonic nanoantenna arrays made out of heavily n-doped InGaAs with increasing levels of free-carrier density, we discriminate between hydrodynamic and dielectric nonlinearities. Most importantly, we demonstrate that the maximum nonlinear efficiency as well as its spectral location can be engineered by tuning the doping level. Crucially, the maximum efficiency can be increased by almost two orders of magnitude with respect to the classical dielectric nonlinearity. Having employed the common material platform InGaAs/InP that supports integrated waveguides, our findings pave the way for future exploitation of plasmonic nonlinearities in all-semiconductor photonic integrated circuits.
光子集成电路中纳米级非线性元件的效率受到电介质非线性光学响应物理极限的阻碍，由于这是一种基本材料特性，无法对其进行调控。在此，我们通过实验证明，掺杂半导体中的超快光学非线性可以被调控，并且能够轻易超越传统未掺杂电介质的非线性。实际上，重掺杂半导体的电子响应具有流体动力学特性，会引入非局部效应以及额外的非线性源。我们的实验结果得到了基于流体动力学模型的全面计算分析的支持。特别是，通过研究由重n掺杂的InGaAs制成的等离子体纳米天线阵列在自由载流子密度不断增加时的三次谐波产生情况，我们区分了流体动力学非线性和电介质非线性。最重要的是，我们证明了可以通过调整掺杂水平来调控最大非线性效率及其光谱位置。关键在于，相对于经典电介质非线性，最大效率可提高近两个数量级。由于采用了支持集成波导的常见材料平台InGaAs/InP，我们的研究结果为全半导体光子集成电路中未来利用等离子体非线性铺平了道路。
