ARTICLES https://doi.org/10.1038/s41565-020-00787-y 1 Samsung Advanced Institute of Technology, Samsung Electronics, Suwon, Republic of Korea. 2 Department of Physics, Hanyang University, Seoul, Republic of Korea. 3 Geballe Lab for Advanced Materials, Stanford University, Stanford, CA, USA. 4 School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon, Republic of Korea. 5 Present address: Department of Physics, Dankook University, Cheonan, Republic of Korea. 6 These authors contributed equally: Junghyun Park, Byung Gil Jeong, Sun Il Kim. ✉ e-mail: jhy.park@samsung.com; hyuck.choo@samsung.com; choibl@skku.edu S patial light modulators (SLMs) regulate the amplitude, phase and polarization of light and serve as the core components of many optical applications, such as digital holographic sys- tems, optical communication modules and biomedical imaging systems 1–4 . The recent emergence of new applications, such as wear- able displays for augmented reality or light detection and ranging (LiDAR) sensors for autonomous vehicles, demands the develop- ment of new SLMs with an improved field of view, speed and reli- ability compared with those of the conventional devices that rely on liquid crystals 5,6 and microelectromechanical systems 7,8 . To meet this demand, the use of active metasurfaces has been explored 9 . Metasurfaces were first investigated as assemblies of pas- sive, static nanoscale optical elements that provided control over the amplitude, phase and polarization of transmitted or reflected light 10–14 , and then evolved into active metasurfaces that could enable ultrafast wavefront manipulation and a wide field of view in a compact form factor 15 . Pioneering studies exploited various tun- able materials and designs, which included transparent conduct- ing oxides 16–19 , phase-change materials 20–22 , semiconductors 23,24 , two-dimensional (2D) materials 25–28 , micromechanical actuators 29 , frequency-gradient sources 30 and liquid crystals 6 . The active metasurfaces reported to date, however, show incom- plete phase modulation below 360° and undesired cross-modulation of the amplitude and phase. This limitation mainly arises from the use of a single control parameter to modulate 2D phenomena, such as transmission or reflection described by complex coefficients that consist of real (r real ) and imaginary (r imag ) parts 9–13 . Complex modulation is a 2D phenomenon, and its control requires the use of two control parameters. This intuitive principle can be verified for most of the passive metasurfaces that successfully demonstrate static wavefront manipulation because these metasurfaces exploit at least two in-plane geometric parameters, such as the width and length or the orientation angle and diameter 11–13,31,32 . To extend the phase modulation range, a recent study reported the use of dual gates in which two identical or opposite voltages were applied; by this approach, a modulation of 300° was reported 19 (Supplementary Section 1 and Supplementary Fig. 1). Here we present an all-solid-state SLM composed of an electri- cally tunable metasurface array (Fig. 1a) designed to demonstrate the two-control-parameter approach in the near infrared (NIR) regime. The array consists of plasmonic nanoresonators whose reflection coefficient can be tuned by applying separate electrical biases V t and V b to the top and bottom electrodes of the nanoresona- tors (Fig. 1b). Detailed numerical and experimental investigations revealed that a careful selection of the operating ranges for V t and V b allowed us to assign one of the two voltages to adjust the real part of the reflection coefficient (r), whereas the other voltage was used to control the imaginary part. Utilizing V t and V b as two separate control knobs, we achieved a completely independent control of the amplitude and phase over 360° and demonstrated an increased All-solid-state spatial light modulator with independent phase and amplitude control for three-dimensional LiDAR applications Junghyun Park  1,6 ✉ , Byung Gil Jeong 1,6 , Sun Il Kim 1,6 , Duhyun Lee 1 , Jungwoo Kim 1 , Changgyun Shin 1 , Chang Bum Lee 1 , Tatsuhiro Otsuka 1 , Jisoo Kyoung  1,5 , Sangwook Kim 1 , Ki-Yeon Yang 1 , Yong-Young Park 1 , Jisan Lee 1 , Inoh Hwang  1 , Jaeduck Jang  1 , Seok Ho Song  2 , Mark L. Brongersma  3 , Kyoungho Ha 1 , Sung-Woo Hwang  1 , Hyuck Choo  1 ✉ and Byoung Lyong Choi  4 ✉ Spatial light modulators are essential optical elements in applications that require the ability to regulate the amplitude, phase and polarization of light, such as digital holography, optical communications and biomedical imaging. With the push towards miniaturization of optical components, static metasurfaces are used as competent alternatives. These evolved to active meta- surfaces in which light-wavefront manipulation can be done in a time-dependent fashion. The active metasurfaces reported so far, however, still show incomplete phase modulation (below 360°). Here we present an all-solid-state, electrically tunable and reflective metasurface array that can generate a specific phase or a continuous sweep between 0 and 360° at an estimated rate of 5.4 MHz while independently adjusting the amplitude. The metasurface features 550 individually addressable nanoresona- tors in a 250 × 250 μm 2 area with no micromechanical elements or liquid crystals. A key feature of our design is the presence of two independent control parameters (top and bottom gate voltages) in each nanoresonator, which are used to adjust the real and imaginary parts of the reflection coefficient independently. To demonstrate this array’s use in light detection and ranging, we performed a three-dimensional depth scan of an emulated street scene that consisted of a model car and a human figure up to a distance of 4.7 m. NATURE NANOTECHNOLOGY | www.nature.com/naturenanotechnology