Cadmium arsenide (Cd3As2), an emerging three-dimensional Dirac semimetal, has recently generated significant interest in the area of ultrafast optics and optoelectronics. However, its nonlinear susceptibility has not been experimentally studied; thus, it is not yet possible to evaluate its potential in nonlinear optics. In this work, we investigate third harmonic generation (THG) in a 100 nm thick Cd3As2 film using broadband infrared femtosecond lasers (across 1500–2350 nm). The χ3 of Cd3As2 (2.30 × 10−19 m2 V−2) is obtained by comparing the THG spectra with a glass substrate, graphene, and monolayer MoS2. We further demonstrate a simple approach to enhance the THG signal by introducing an underlying planar micro-cavity. An enhancement of about 420 times in the THG signal was recorded at ≃1560 nm. Our results indicate that Cd3As2 thin films can provide a similar platform for nonlinear optics with respect to graphene and may offer unique potential in the mid-infrared due to its broadband light–matter interaction and excellent tunability.

中文翻译：

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狄拉克半金属 Cd3As2 中的三次谐波生成

砷化镉 (Cd3As2) 是一种新兴的三维狄拉克半金属，最近在超快光学和光电子领域引起了极大的兴趣。然而，其非线性磁化率尚未经过实验研究；因此，目前还无法评估其在非线性光学方面的潜力。在这项工作中，我们使用宽带红外飞秒激光器（跨越 1500-2350 nm）在 100 nm 厚的 Cd3As2 薄膜中研究三次谐波的产生（THG）。Cd3As2 (2.30 × 10−19 m2 V−2) 的 χ3 是通过将 THG 光谱与玻璃基板、石墨烯和单层 MoS2 进行比较而获得的。我们进一步展示了一种通过引入底层平面微腔来增强 THG 信号的简单方法。在 ≃1560 nm 处记录到 THG 信号增强了约 420 倍。