Controllable Polarization‐Insensitive and Large‐Angle Beam Switching with Phase‐Change Metasurfaces

Abstract

The development of high‐efficiency compact non‐mechanical beam tuning devices has attracted a lot of attention for light detection and ranging, augmented reality display, and chip‐to‐chip communication. Owing to the fast wavefront manipulation in an ultra‐thin dimension, metasurfaces have been regarded as potential substitutes for traditional tunable optical components toward further miniaturization and low power consumption. However, most beam tuning metasurfaces currently are polarization‐sensitive and designed to work in reflection mode, which limit their applications in integrated optical systems for full‐range steering. In this paper, a transmission mode polarization‐insensitive beam switching metasurface based on nonvolatile phase‐change material Ge2Sb2Te5 is proposed and experimentally demonstrated at the telecommunication wavelength. The high transmission efficiency with a large switching angle of up to 75° is achievable for potentially full‐range beam steering applications. As a proof of concept, the transmitted beam with a switching angle of 15° and directivity of 82.4% is demonstrated. In addition, by controlling the phase transition in the intermediate states, the metasurface can be used as a tunable beam splitter to control the ratio of the beam power between two predesigned transmission angles. The demonstrated phase‐change metasurfaces pave the way for achieving high‐efficiency dynamic beam steering for various important applications.

Recent Advances in Tunable Metasurfaces: Materials, Design, and Applications

“…The inverse method aims to achieve the optimum custom-defined performance. Different inverse design optimization techniques have been developed, including PSO, − GA, , emerging ML , and AI models. , Figure summarizes typical inverse and forward design methodologies, which have been adopted for tunable metasurface design. PSO is a typical swarm-intelligence algorithm that imitates the collective behavior observed in social animals, such as birds and fish .…”

Enabling Active Nanotechnologies by Phase Transition: From Electronics, Photonics to Thermotics

“…Furthermore, exploiting PCMs to control the flow of different polariton waves can further expand their applications and manipulate light on-chip at the nanoscale in a programmable fashion. Therefore, many types of tunable metasurfaces have been demonstrated, including tunable absorbers and filters, ,− phase masks, , beam steering, ,− display, ,, metalens, − and enhanced third-harmonic generation (THG) . On the other side, memory units, , switches and modulators, − programmable neural networks, and arithmetic operations are some of the examples of tunable integrated photonic devices proposed.…”

Optical Properties of Electrochemically Gated La1−xSrxCoO3−δ as a Topotactic Phase‐Change Material

“…[3] While traditional metasurfaces have a fixed geometry and therefore a static optical response, it is possible to add active tunability to these systems by pairing them with materials that undergo controllable refractive index changes to create active metasurfaces. [4,5] Various modulation mechanisms and materials have been used to achieve this tunability, including electrostatic modulation in materials like transparent conducting oxides [6][7][8][9] and graphene, [10,11] thermally-mediated phase changes in Ge x Sb y Te z (GST) [12][13][14][15][16][17][18] and VO 2 , [19][20][21][22][23] electro-and photochromic materials, [24][25][26][27][28] nonlinear materials, [29] and liquid crystals. [30,31] Collectively, these tunable materials systems have enabled dynamic behavior such as reflection [15,19,25] and transmission [8,23] modulations, color switching, [24,31] and high-efficiency beam steering, [9,[12][13][14] with numerous applications in the visible and infrared.…”

“…[4,5] Various modulation mechanisms and materials have been used to achieve this tunability, including electrostatic modulation in materials like transparent conducting oxides [6][7][8][9] and graphene, [10,11] thermally-mediated phase changes in Ge x Sb y Te z (GST) [12][13][14][15][16][17][18] and VO 2 , [19][20][21][22][23] electro-and photochromic materials, [24][25][26][27][28] nonlinear materials, [29] and liquid crystals. [30,31] Collectively, these tunable materials systems have enabled dynamic behavior such as reflection [15,19,25] and transmission [8,23] modulations, color switching, [24,31] and high-efficiency beam steering, [9,[12][13][14] with numerous applications in the visible and infrared. The phasechange materials VO 2 and GST have been especially popular for infrared applications, including telecommunications [12][13][14][19][20][21]…”

“…[30,31] Collectively, these tunable materials systems have enabled dynamic behavior such as reflection [15,19,25] and transmission [8,23] modulations, color switching, [24,31] and high-efficiency beam steering, [9,[12][13][14] with numerous applications in the visible and infrared. The phasechange materials VO 2 and GST have been especially popular for infrared applications, including telecommunications [12][13][14][19][20][21]23] and thermal imaging, [15,16] due to their significant refractive index changes in the near-and mid-infrared. VO 2 undergoes a monoclinic-to-rutile transformation at 68 °C, where the room-temperature insulating phase shows high index and low loss, while the high-temperature metallic phase is highly lossy.…”