Sandia National Laboratories, Albuquerque, NM, 87185, USA.
Institute of Applied Physics, Abbe Center of Photonics, Friedrich Schiller University Jena, Albert-Einstein-Str. 15, 07745, Jena, Germany.
Nat Commun. 2018 Jun 28;9(1):2507. doi: 10.1038/s41467-018-04944-9.
A frequency mixer is a nonlinear device that combines electromagnetic waves to create waves at new frequencies. Mixers are ubiquitous components in modern radio-frequency technology and microwave signal processing. The development of versatile frequency mixers for optical frequencies remains challenging: such devices generally rely on weak nonlinear optical processes and, thus, must satisfy phase-matching conditions. Here we utilize a GaAs-based dielectric metasurface to demonstrate an optical frequency mixer that concurrently generates eleven new frequencies spanning the ultraviolet to near-infrared. The even and odd order nonlinearities of GaAs enable our observation of second-harmonic, third-harmonic, and fourth-harmonic generation, sum-frequency generation, two-photon absorption-induced photoluminescence, four-wave mixing and six-wave mixing. The simultaneous occurrence of these seven nonlinear processes is assisted by the combined effects of strong intrinsic material nonlinearities, enhanced electromagnetic fields, and relaxed phase-matching requirements. Such ultracompact optical mixers may enable a plethora of applications in biology, chemistry, sensing, communications, and quantum optics.
混频器是一种将电磁波组合以产生新频率的非线性器件。混频器是现代射频技术和微波信号处理中无处不在的组件。开发用于光学频率的多功能混频器仍然具有挑战性：此类设备通常依赖于较弱的非线性光学过程，因此必须满足相位匹配条件。在这里，我们利用基于 GaAs 的介电超表面来演示一种光学频率混频器，该混频器可以同时产生新的 11 个频率，涵盖紫外到近红外。GaAs 的偶数阶和奇数阶非线性使我们能够观察到二次谐波、三次谐波和四次谐波产生、和频产生、双光子吸收诱导的光致发光、四波混频和六波混频。这些七个非线性过程的同时发生得益于强固有材料非线性、增强的电磁场和放宽的相位匹配要求的综合影响。这种超紧凑的光学混频器可能在生物学、化学、传感、通信和量子光学等领域实现多种应用。
