Recent advancements in nonlinear optical metasurfaces have the potential to redefine communication technologies and medical diagnostics. These uniquely engineered surfaces, which are smaller than light’s wavelength, signify a promising direction for future developments such as quantum light sources and innovative diagnostic devices. Led by Professor Jongwon Lee from the Department of Electrical Engineering at UNIST, a pivotal study showcased experimental realizations of electrically tunable third-harmonic generation (THG) using intersubband polaritonic metasurfaces in conjunction with multiple quantum wells (MQWs).
This research, published in *Light: Science & Applications*, presents remarkable results. The team achieved a modulation depth for the THG signal reaching an impressive 450%, while successfully suppressing zero-order THG diffraction by 86%. The capacity for local phase tuning exceeded 180 degrees, enabling exquisite control over the light propagation. Furthermore, they demonstrated THG beam steering capabilities leveraging phase gradients, paving the way for electrically adjustable and flat nonlinear optical components with diverse functionalities.
Nonlinear optics is a field that investigates the complex interactions between light and matter, allowing for the generation of multiple wavelengths from a single light source. This multi-wavelength capability can significantly boost information transmission rates compared to conventional methods that rely on single-wavelength lasers. A familiar application of nonlinear optics is the ubiquitous green laser pointer, which provides a glimpse into the practical utility of such technologies.
The metasurface technology developed by Professor Lee’s team holds the promise of compact and lightweight optical instruments. Imagine laser devices that are no thicker than a sheet of paper or materials denser than human hair—a vision that aligns with the incoming paradigm of miniaturization in technology. Previous endeavors faced barriers regarding electrical control; this new approach overcomes those hurdles, representing a breakthrough in the field of nonlinear optics.
Arguably one of the most groundbreaking aspects of this research is the introduction of the world’s first voltage-controlled second-harmonic generation (SHG) technology. This innovation allows for independent modulation of both intensity and phase of the THG signal, equipping the metasurface with the ability to control not only wavelength but also light’s intensity and phase. Professor Lee encapsulates the significance of their findings succinctly, stating, “This advancement allows for unprecedented control of light.”
The implications of this technology are vast and varied. By harnessing the intensity and phase of nonlinear THG through electric means, new frontiers emerge for applications ranging from cryptography and dynamic holography to advanced quantum sensors and communication systems. The research underscores the importance of the semiconductor layer and metallic structure in defining the properties of the optical metasurface. Researchers like Seongjin Park emphasize that the limit of this technology could extend far beyond current applications, heralding a new era in optical engineering.
The breakthroughs in nonlinear optical metasurfaces reveal vital insights into the future of optical technology, with implications that could extend to diverse fields and applications. As we stand at the forefront of these technological advancements, the potential for innovation appears boundless.