Open Access
Add to BibSonomy
Abstract
A Fourier lens can perform the Fourier transform of an incident wavefront at the focal plane. This paper reports a metasurface-based Fourier lens fed by compact plasmonic optical antennas for wide-angle beam steering. The metasurface, composed of six elements with different configurations covering the 2π phase range, features a large field-of-view (FOV) of ±50°. A novel plasmonic optical antenna for broadside radiation is then designed as the feed source of the metasurface. The proposed antenna has ultra-compact size of 0.77λ × 1.4λ, and achieves a high directivity of 9.6 dB and radiation efficiency of over 80% at the wavelength of 1550 nm. Full-wave simulations are carried out to evaluate the performances of the designed metasurface-assisted beam steering device. The results show that this device can achieve a maximum directivity of 21.5 dB at broadside radiation. Compared to conventional Yagi-Uda antenna feed, a directivity enhancement of about 2.7 dB can be obtained, exhibiting a great superiority of the proposed feed antenna. In addition, a large beam steering range of ±50° can be achieved with an acceptable gain drop of 2.83 dB. With the advantages of wide beam steering range, good radiation characteristics, small footprint, and ease of integration, the proposed metasurface-assisted beam steering device would be a promising candidate for integrated photonic applications, including wireless optical communications, light detection and ranging, and augmented reality.
© 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement
1. Introduction
Optical beam scanners are an essential component in various applications, including light detection and ranging (LiDAR) [1,2], free-space communications [3], imaging [4,5], and holographic three-dimensional display [6]. Traditional devices achieve dynamic optical beam scanning by mechanically rotating reflective mirrors, suffering from low operating speed and are vulnerable to vibrations. In recent years, with the rapid development of photonic integrated circuits (PICs), several beam steering technologies have been investigated, such as optical phased arrays (OPAs) [7–9], micro-electro-mechanical systems (MEMS) [10], and liquid-crystal spatial light modulators [11]. OPAs are widely considered an outstanding beam steering technology for their potential in realizing chip-scale systems and all-solid-state inertia-free beam steering. In these OPAs, beamforming and wavefront manipulation can be achieved by independently controlling the amplitude and phase of each antenna element in the array. Generally, a far-field beam with slight divergence is always pursued for a large detection distance. For this purpose, numerous antenna elements are needed to construct a coherent radiation array, leading to the increment of the number of phase shifters, resulting in high power consumption and complex control circuits. For example, an OPA composed of one thousand antenna elements can cost power consumption as large as tens of watts [12].
Lens-based beam-steering devices have been demonstrated with low power consumption [13–15]. By placing an off-lens above an emitter array, the far-field beam can be correspondingly manipulated according to the shape of the lenses. Recently, a variety of lenses with different configurations have been utilized to expand the scanning angles and improve the far-field beam quality [16–18]. However, these devices require bulky lens components, and the mounting fixtures are generally several millimeters or centimeters away from the emitter array, making integration with chips complicated. To tackle this issue, metasurface-based lenses have emerged as a promising alternative to traditional bulky ones due to their advantages in ultrathin profile and planar configurations. For example, an all-dielectric metasurface doublet is proposed to improve the wavelength-tuning efficiency, demonstrating a steering efficiency enhanced factor of 3.1. The enhanced factor is defined as the overall beam steering range ratio with/without the metasurface [19]. Besides, in [20], two-dimensional beam steering is achieved by integrating a metalens above a switchable micro-ring emitter array, where the metalens collimates the radiated energy from these micro-ring emitters, and the light radiated from the emitters in different positions can be correspondingly converted to highly directional beams in different directions. Finally, a FOV of 12.4°×26.8° is obtained. Two major drawbacks in the metalens-assisted beam steering devices are the off-axis aberration of metalens under a large incident angle and blind zones within the FOV due to the discrete beam steering. To implement the aberration correction, doublet metalenses have been proposed in [21,22], with the achromatic aberration in the incident angle range of about 30° achieved. Meanwhile, a one-dimensional (1-D) Fourier metasurface made of dielectric waveguide resonators is introduced to perform 1-D Fourier transform even within an incident angle of 0 ∼ 60° [23], revealing the feasibility of wide-angle operations of the metasurface. On the other hand, to suppress the blind zone, the emitters should be placed as densely as possible [24], which requires the feed antenna to have a small footprint.
The far-field radiation properties of the metasurface-assisted beam steering device are determined by the metasurface's designed parameters (e.g., the phase distributions, aperture sizes, and focal distance) and also by the illumination from the feed structure. Therefore, the feed antenna also plays a crucial role in designing such beam steering devices. For the emitters arranged at the focal plane of the metasurface, the light radiated from the focal point can be converted into a plane wave in a specific direction. The feed antenna should preferably be as small as an ideal point source to obtain a highly directional beam. However, the most commonly used radiators in the optical frequency range are grating antennas, as adopted in [13–17,19,20]. Their typical sizes of several wavelengths in transverse and longitudinal directions are much larger than the focal spot sizes, resulting in the performance deterioration of the device. It is well known that dipole antennas are usually employed as feed antennas in the microwave frequency range due to their subwavelength sizes and stable radiation patterns [25]. Similarly, various optical nano-antennas, e.g., dipole antenna, Yagi-Uda antenna, and bowtie antenna, have been investigated [26]. However, due to the planar terminal-opening structure of these antennas, it is difficult to achieve high broadside radiation efficiency. Therefore, designing a compact antenna with high performance and a small footprint is very meaningful and challenging.
This paper designed and numerically demonstrated a metasurface-based Fourier lens fed by compact plasmonic optical antennas. The metasurface is made of silicon ellipse posts on a silica substrate, which converts the near-field light radiated from different off-center positions to far-field high-directivity beam in different directions. Besides, a novel plasmonic nano-antenna is proposed as the feed source of the metasurface. The designed plasmonic antenna can achieve high-efficiency broadside radiation with ultra-compact sizes of 0.77λ×1.4λ. Simulated results show that the proposed metasurface-assisted beam steering device can achieve a ±50° beam steering range with stable high-directivity radiation patterns by tuning the radiation antenna. Besides, a Yagi-Uda antenna is employed as the feed source of the metasurface for a comparison. It demonstrates that higher device directivity can be obtained using the proposed antenna feed. We believe the proposed antenna and the metasurface-assisted beam steering device with high performances and a small footprint will provide a significant step in developing high-density PICs.
2. Design and results
2.1 Design of the metasurface-based Fourier lens
As verified in [27,28], metasurface elements that provide a two or three-bit transmission phase are sufficient to implement a metasurface antenna with fairly good performance. In this section, six kinds of elements with different configurations are employed to construct a metasurface-based Fourier lens, which can perform 2D Fourier transform within a large incident angle range. As shown in Fig. 1(a), the unit cell consists of a high refractive index polysilicon elliptic nanopillar (refractive index n = 3.67) [29] on top of a semi-infinite silica substrate (refractive index n = 1.444). The period p of the unit cell and the height h of the nanopillar are optimized to 600 nm and 1100 nm, respectively, for high transmissivity and large phase-shifted range under reasonable structural parameter variations (e.g., b and a, the sizes of ellipse nanopillar in x- and y-directions, respectively). For a plane wave incidence, the nanopillar functions as a waveguide, where the nanopillars with different sizes exhibit different propagation constants. Therefore, by adjusting the ellipse parameters a and b, full 0 ∼ 2π phase control can be obtained. To determine the phase and transmission dependences of a and b, parameter studies are carried out by Ansys HFSS, a commercially available finite element method (FEM) simulation software package. In the simulations, periodic boundary conditions along x- and y-directions and Floquet ports along z-direction are applied, respectively. At the operating wavelength of 1550 nm, an x-polarized plane wave is at normal incidence from the bottom of the substrate.
Fig. 1. (a) 3D schematic view and top view of the unit cell of the designed metasurface, with the polysilicon elliptic nanopillar on top of a semi-infinite silica substrate. Under the normal incidence of the x-polarized plane wave at 1550 nm, (b) the transmission as a function of b and a. (c) The phase as a function of b and a. (d) The corresponding transmission and phase of the designed six elliptic nanopillars versus the incident angle. The sizes characterizing the six elements with the phased-shift value from −150° to 150° are: b = 500, 475, 400, 300, 150, and 350 nm, and a = 175, 150, 150, 175, 150, and 375 nm. p = 600 nm and h =1100 nm.
The transmission coefficients and corresponding phases as functions of parameters a and b are shown in Figs. 1(b) and (c), respectively. Benefiting from the all-dielectric element design, full 0 ∼ 2π phase control and high transmission over 90% can be enabled simultaneously. Next, six elliptic nanopillars with an incremental propagating phase of π/3 (numbered from 1 to 6) are elaborately selected as the fundamental metasurface elements to construct a Fourier lens. The parameters characterizing the elements from 1 to 6 are b = 500, 475, 400, 300, 150, and 350 nm, and a = 175, 150, 150, 175, 150, and 375 nm, respectively. Besides, to achieve wide-angle operations, all the metasurface elements must possess high transmissivity even at a large incident angle. Hence, the phase and transmission coefficients of the designed six elements as functions of incident angle are given in Fig. 1(d), where the plane wave is incident in the xoz plane. The results exhibit that the phase variation for all the six elements is below 0.21π and the transmissivity is higher than 85% even when the incident angle is tilted by 40°. These are key factors to achieve metasurface with a wide FOV.
After the design of the metasurface element, the different phase-shifted elements can be arranged at different positions to fit the desired phase profile. In our design, a quadratic phase profile is employed to design a metasurface with a wide FOV, and the phase profile is as follows [30]:
where λ is the free-space wavelength, F is the focal length of the metasurface, nsub represents the substrate's refractive index (SiO2 in our case), and x and y are the coordinate positions along the x- and y-axis. A parabolic phase profile may be more accurate to focusing with high resolution but with a small FOV. By contrast, although the metasurface with a quadratic phase profile may suffer from spherical aberration, which will reducec the resolution, the wide-angle operations can be enabled [31]. The schematic diagram of converting the incident plane waves to the focused beams via the designed metasurface is illustrated in Fig. 2(a). For a plane wave incident at an incident angle θ, a corresponding focal point is located at the focal plane, with the horizontal offset of l = Fsinθ/nsub with respect to the focal position at normal incidence. Conversely, suppose the feed antennas are arranged at different positions in the focal plane. In that case, the metasurface can be illuminated by one of the antennas at a time, thereby obtaining the far-field radiation beams with different scanning angles. It can be inferred that the number of feed antennas determines the resolvable spots in the far-field.Fig. 2. (a) With an incident angle of θ, the focal spot will be shifted by a distance Fsinθ/nsub along the focal plane. (b) The discrete phase distributions of the designed metasurface. At 1550 nm, the corresponding electric-field (E-field) distributions on the xoz plane with the incident angle of (c) 0°, (d) 10°, (e) 20°, (f) 30°, (g) 40°, and (h) 50°. The aperture sizes of the metasurface are 24.6 × 24.6 µm2, and the focal distance is 10 µm.
Next, the metasurface is constructed by the designed six elements. The designed metasurface is composed of 41-unit cells along both x and y directions with the aperture sizes of 24.6×24.6 µm2. The focal length F is designed to be 10 µm, leading to an F/D ratio of about 0.41. Once the aperture sizes and focal length are determined, the phase distributions in the transmitted region can be calculated according to Eq. (1). Since only six-phase states with the quantization phase of 60° can be offered, some approximations should be adopted to make these elements suitable for the metasurface design. The strategy for assigning the phase-correction value for each element of the 6-state metasurface is expressed as follows:
2.2 Design of the feed antenna
Plasmonic slot waveguide can guide waves at a subwavelength scale, making it attractive for high-density optical circuits. In this section, an ultra-compact all-plasmonic nanoantenna based on the plasmonic slot waveguide is proposed for high-performance broadside radiation. The geometry of the proposed structure is depicted in Fig. 3(a). The device is made up of single-layer silver with a thickness t of 100 nm and is embedded in the SiO2 medium. The structure includes three sections: transmission section, radiation section, and a reflector at the end. In the first section, the plasmonic slot mode is excited in the plasmonic slot waveguide, where the width w and s of the silver stripes and the slot are set to 200 nm and 340 nm to minimize the propagation loss, respectively. The corresponding E-field distributions of the plasmonic slot waveguide mode are illustrated in Fig. 3(b), and most of the optical fields are confined within the slot. The slot width is periodically varied along the propagation direction (x-direction) in the second region to radiate the guided waves into free space while always keeping w constant. The varied slot width will result in a periodical modulation of the field intensity in the waveguide. According to [33], spatial amplitude modulation corresponds to shifting the spatial spectrum of the modulating wave up to the carrier spatial frequency. If the spatial frequency falls within the radiation region, the guided wave in the waveguide structure can be radiated into free space. Therefore, the amplitude modulation caused by the varied slot width makes the plasmonic slot waveguide a leaky-wave antenna. It is clear that the operating principle of the proposed antenna is different from traditional dipole antennas, where they rely on the resonance of the arms to radiate the energy into free space. As shown in Fig. 3(a), the sine function is used to characterize the slot width in the second section, which is defined as s’(x) = s-4*Asin(2πx/ps), where A and ps are the modulation index and period, respectively. In our design, A and ps are set to 70 nm and 900 nm for a large radiation rate and perfect broadside radiation. A reflector is placed at the end of the antenna to reduce the size and enhance the gain of the antenna. The dimensions lr and wr of the reflector are 1200 nm and 300 nm, respectively, and the gap g between the reflector and the antenna is 200 nm. The reflector can reflect the electromagnetic waves constructively back to the antenna so that the input energy can be radiated to the broadside direction as much as possible.
Fig. 3. (a) Schematic top view of the proposed plasmonic slot antenna. (b) E-field distributions of the plasmonic slot waveguide at 1550 nm. E-field distributions (c) on the xoy plane and (d) on the xoz plane at 1550 nm. w = 200, s = 340, A = 70, ps = 900, lr = 1200, wr = 300 and g = 200, all in nm.
Numerical calculations are carried out to demonstrate the designed antenna’s performance. In the simulations, the permittivity of silver is fitted using Drude model with ɛinf = 5, ωp = 13.4 × 1015 rad/s and Г = 1.12 × 1014 1/s [34]. At the wavelength of 1550 nm, the E-field distributions of the designed antenna on the xoy plane are depicted in Fig. 3(c). It can be seen that most of the optical fields are confined within the slot, and the field strength inside the slot varies with the slot width. Meanwhile, with the help of the reflector, most energy can be reflected at the end of the antenna so that no apparent end-fire radiation can be observed. However, in the plasmonic slot waveguide with a large slot size, the electromagnetic waves will become fast waves and then radiate into free space. The corresponding E-field distributions on the xoz plane are illustrated in Fig. 3(d). Clear wavefronts in both the upper half-space and the lower half-space can be seen, implying near-perfect broadside radiation. In addition, unidirectional radiation can also be achieved by placing an additional metal ground below the antenna [35].
To evaluate the performances of the designed antenna, the antenna parameters, e.g., port reflection coefficient S11, peak directivity, and radiation efficiency, as a function of wavelength are plotted in Fig. 4(a). Antenna gain is defined as G = 4πηP(θ,φ)/Pe = η*D, and the realized gain is defined as Gr = G*(1-S112), where η, D, P(θ,φ) and Pe represent radiation efficiency, antenna directivity, the radiation power density at the specified angle in free space and total radiated power, respectively. The antenna gain describes the ability of the antenna to convert the input power into free-space radiation in the specified directions, and the radiation efficiency represents system loss. Generally, all-plasmonic antennas will be very lossy due to the high absorption loss of metals, consequently resulting in a low radiation efficiency [36]. Thanks to the compact size of the proposed antenna, over 80% radiation efficiency can be achieved in our design, as seen in Fig. 4(a). Meanwhile, within the wavelength range of 1500 ∼ 1613 nm, the antenna directivity ranges from a minimum value of 8.36 dB to a maximum value of 10.2 dB. The port reflection coefficient remains below −13.8 dB, indicating the high performance of the proposed design. Due to the reduction in antenna sizes, the reflector plays a vital role in achieving high directivity. Figure 4(b) shows the corresponding E-plane (yoz plane) and H-plane (xoz plane) radiation patterns for the antenna with/without the reflector at 1550 nm, respectively. The maximum realized gain achieved in the broadside direction without the reflector is about 6.88 dB. In addition, a relatively high gain of 2.5 dB can be observed in the undesired end-fire direction. With the reflector, the end-fire radiation is reduced, and the gain in the broadside radiation is increased by 1.69 dB, accordingly. Finally, the 3D far-field patterns at the wavelengths of 1500 nm, 1550 nm, and1613 nm are depicted in Fig. 4(c). The ultra-compact sizes, stable radiation patterns, as well as wideband operation characteristics make the proposed antenna suitable as a feed source for various metasurfaces. These characteristics are also very promising for the applications such as wireless optical communications [37], optical links [38], nano-photonic coherent imager [39], and so on.
Fig. 4. (a) Port reflection coefficient S11, peak directivity, and radiation efficiency as a function of wavelength. (b) Corresponding E-plane (yoz plane) and H-plane (xoz plane) radiation patterns at 1550 nm for the antenna with/without the reflector, respectively. (c) 3D far-field patterns at the wavelengths of 1500 nm, 1550 nm, and 1613 nm, respectively.
2.3 Performances of the designed metasurface with the proposed antenna feed
After designing the metasurface and the feed antenna, the wide-angle scanning characteristics of the metasurface-assisted beam steering device at the single wavelength of 1550 nm are also verified by numerical simulations. The 3D schematic view of the proposed device is shown in Fig. 5(a). An airbox encloses the structure in the simulations, and PML absorption boundaries are applied to absorb incident light with minimal reflections. As demonstrated in Section 2.1, the position with maximum E-field is located about 7 ∼ 9 µm away from the metasurface, so in our design, the feed antennas are placed 8.5 µm below the metasurface. To achieve a beam steering range of ±50°, the positions of the feed antenna for different scanning angles should be deviated from the center position along the x-axis by l = Fsinθ/nsub. In this design, the values are l = 0, ±1.2, ±2.37, ±3.46, ±4.45, and ±5.3 µm, respectively. From + x-axis to -x-axis direction, these feed antennas are numbered from #1 to #11, and each antenna element can be individually excited so that 11 beams can be obtained. Furthermore, to show the superiority of the proposed feed antenna, a Yagi-Uda antenna with the same parameters as presented in [26] is also used as a feed source for comparison. The structures and corresponding radiation patterns of the proposed antenna and the referenced Yagi-Uda antenna are illustrated in the inset of Fig. 5(a). Much lower end-fire radiation can be seen in our proposed design.
Fig. 5. (a) 3D schematic view of the proposed metasurface-assisted beam steering device. The inset shows the structure and corresponding far-field distributions of proposed structure and the referenced Yagi-Uda antenna, respectively. (b) Corresponding E- and H-plane radiation patterns of the metasurface fed by the proposed antenna and Yagi-Uda antenna, respectively. (c) Simulated radiation patterns on the xoz plane when antenna #1 to #11 is excited separately.
The corresponding E- and H-plane radiation patterns of the metasurface fed by the proposed antenna and Yagi-Uda antenna are presented in Fig. 5(b), respectively, where centrally-located antenna (#6 element) is excited for broadside radiation. For the Yagi-Uda antenna feed, the device achieves a maximum directivity of 18.8 dB, and nearly the same beamwidth in E-plane and H-plane can be observed. As expected, a higher directivity of 21.5 dB is obtained by using the proposed antenna feed, indicating a 2.7 dB enhancement in device directivity. In addition, it is worth noting that for the proposed feed antenna, the beamwidth in H-plane is much narrow than that in E-plane, as can be seen from Fig. 4(b). However, in the proposed metasurface-assisted beam steering device, it can be seen that the far-field E-plane pattern becomes narrower than H-plane by comparing the black and red solid curves in Fig. 5(b). According to the analysis in [40], for a metasurface with a given aperture size D, power pattern of each feed has an optimal focal length F to obtain maximal directivity. Generally, a narrower feed pattern requires a larger F to achieve this goal. It implies that while keeping D constant, the beamwidth of the H-plane pattern can be reduced by increasing F, thereby further enhancing the gain of the proposed device, which will be discussed in the next section. Figure 5(c) shows the simulated radiation patterns on the xoz plane when antenna #1 to #11 are excited separately. It can be seen that beam steering within the angular range of ±50° can be achieved with the gain variations of less than 2.83 dB. In addition, the first sidelobe level and the cross-polarization level for all the patterns are below −15 dB and −20 dB, respectively.
3. Discussion
The metasurface-assisted beam steering device has been demonstrated a wide-angle beam steering ability beyond ±50° with an increment of discrete scanning angle of 10°. However, due to the large crossover level between adjacent beams, scanning blind zones will also exist. The number of feed antennas can be increased in the focal plane to obtain more discrete beams to solve this problem. Benefiting from the compact size of the proposed feed antenna, the minimum spacing between neighbor feed antennas can be reduced to subwavelength scales, thus enabling high-density integration with a small footprint.
On the other hand, due to the relatively high directivity of the designed feed antenna, it can be inferred that higher directivity of the proposed device can be achieved by further increasing the focus-to-diameter ratio F/D. In this section, simulations are performed to obtain the corresponding directivity of this device at different F/D, where the aperture size D of the metasurface is kept constant throughout, and only F is changed during the simulations. It should be noted that when F changes, the phase distributions across the metasurface should be recalculated according to Eq. (1), and the identical phase approximates are adopted. Finally, the normalized H-plane radiation patterns as a function of F/D are plotted in Fig. 6(a), and the inset shows the partial enlarger details. It can be seen when F/D varies between 0.5 ∼ 1, the beamwidth in H-plane is gradually reduced with the increase of F/D, so that higher device directivity can be obtained. The peak directivity of the device versus F/D is plotted in Fig. 6(b). It can be seen that a maximal directivity of about 27.8 dB can be achieved at F/D = 1.
Fig. 6. (a) Normalized H-plane radiation patterns at the wavelength of 1550 nm as a function of F/D. (b) Directivity of the metasurface-assisted beam steering device versus F/D. (c) Schematic view on the xoz plane of the metasurface with different focal lengths ranging from F to F2, corresponding to a half aperture angle of the triangle from β to β2.
The increasing directivity can be explained by Fig. 6(c). For a given aperture size D, the half aperture angle β of the triangle will decrease accordingly with the increase of F. As β decreases, smaller phase errors and more uniform amplitude distributions can be achieved across the metasurface aperture, leading to a higher illumination efficiency. Meanwhile, the spillover efficiency, which represents the energy that is not intercepted by the metasurface, will decrease with the decrease of β. Therefore, to obtain a high aperture efficiency, there is a tradeoff between the illumination efficiency and the spillover efficiency [41], which exhibits a limitation on the directivity of a metasurface under a given aperture size. On the other hand, as seen in Fig. 6(c), when focal length increases from F to F2, the deviated positions of the feed antenna for different scanning angles satisfy Fsinθ/nsub < F1sinθ/nsub < F2sinθ/nsub. To maintain a high spillover efficiency for the edge feed antenna, the physical aperture of the metasurface should be enlarged.
Therefore, when designing the metasurface-assisted beam steering device, a relatively small F/D is first considered so that the metasurface can intercept the energy radiated by the antennas at different positions. Then, the aperture size D and the focal length F can be increased simultaneously to enhance the device's directivity.
4. Conclusion
A metasurface-assisted beam steering device is proposed in this paper. Firstly, a 2D metasurface-based Fourier lens with a wide FOV is designed at the wavelength of 1550 nm, and numerical simulations verify the focusing characteristics of the designed metasurface at different incident angles. Then, a novel feed antenna with ultra-compact sizes of 0.77λ×1.4λ for broadside radiation is designed, achieving a directivity and radiation efficiency of 9.6 dB and 80%, respectively. Besides, good port reflection coefficients and stable radiation patterns within the wavelength range of 1500 ∼ 1613 nm also ensure wideband operations of the designed antenna. Finally, the full-wave results of the proposed metasurface-assisted beam steering device show that a large beam steering range of ±50° can be achieved under a gain variation of below 2.83 dB. Compared to conventional Yagi-Uda antenna feed, a directivity enhancement of about 2.7 dB can be obtained, exhibiting a significant superiority of the proposed antenna. Besides, the device's directivity as a function of the focal distance F/D is investigated for a given metasurface aperture size D. Due to the small divergence angle of the designed feed antenna, smaller phase errors and more uniform illuminating amplitude across the metasurface can be achieved with the increase of F/D, resulting in the directivity enhancement of the device. In addition, taking advantage of the proposed feed antenna, high-performance 2-D beam steering, and wideband operations would be achieved by elaborately designing the metasurface element. The proposed metasurface-assisted beam steering device, featuring high directivity, wide beam steering range, and minimal footprint, would be attractive for the applications of all-solid-state LiDAR, unmanned driving, 3D imaging etc.
Funding
National Natural Science Foundation of China (U20A20165); Fundamental Research Funds for the Central Universities (ZYGX2019Z005).
Disclosures
The authors declare no conflicts of interest.
Data availability
Data underlying the results presented in this paper are not publicly available at this time but may be obtained from the authors upon reasonable request.
References
1. C. V. Poulton, A. Yaacobi, D. B. Cole, M. J. Byrd, M. Raval, D. Vermeulen, and M. R. Watts, “Coherent solid-state LIDAR with silicon photonic optical phased arrays,” Opt. Lett. 42(20), 4091–4094 (2017). [CrossRef]
2. C. P. Hsu, B. Li, B. Solano-Rivas, A. R. Gohil, P. H. Chan, A. D. Moore, and V. Donzella, “A Review and Perspective on Optical Phased Array for Automotive LiDAR,” IEEE J. Sel. Top. Quantum Electron. 27(1), 1–16 (2021). [CrossRef]
3. C. V. Poulton, M. J. Byrd, P. Russo, E. Timurdogan, M. Khandaker, D. Vermeulen, and M. R. Watts, “Long-Range LiDAR and Free-Space Data Communication with High-Performance Optical Phased Arrays,” IEEE J. Sel. Top. Quantum Electron. 25(5), 1–8 (2019). [CrossRef]
4. M. Raval, A. Yaacobi, and M. R. Watts, “Integrated visible light phased array system for autostereoscopic image projection,” Opt. Lett. 43(15), 3678–3681 (2018). [CrossRef]
5. J. Sun, E. Timurdogan, A. Yaacobi, E. S. Hossein, and M. R. Watts, “Large-scale nanophotonic phased array,” Nature 493(7431), 195–199 (2013). [CrossRef]
6. G. Yang, W. Han, T. Xie, and H. Xie, “Electronic holographic three-dimensional display with enlarged viewing angle using non-mechanical scanning technology,” OSA Continuum 2(6), 1917–1924 (2019). [CrossRef]
7. A. Yaacobi, J. Sun, M. Moresco, G. Leake, D. Coolbaugh, and M. R. Watts, “Integrated phased array for wide-angle beam steering,” Opt. Lett. 39(15), 4575–4578 (2014). [CrossRef]
8. K. Komatsu, Y. Kohno, Y. Nakano, and T. Tanemura, “Large-Scale Monolithic InP-Based Optical Phased Array,” IEEE Photonics Technol. Lett. 33(20), 1123–1126 (2021). [CrossRef]
9. Y. Zhang, Y. Ling, K. Zhang, C. Gentry, D. Sadighi, G. Whaley, J. Colosimo, P. Suni, and S. J. B. Yoo, “Sub-wavelength-pitch silicon-photonic optical phased array for large field-of-regard coherent optical beam steering,” Opt. Express 27(3), 1929–1940 (2019). [CrossRef]
10. Y. Wang, G. Zhou, X. Zhang, K. Kwon, P. A. Blanche, N. Triesault, K. Yu, and M. C. Wu, “2D broadband beamsteering with large-scale MEMS optical phased array,” Optica 6(5), 557–562 (2019). [CrossRef]
11. J. R. Lindle, A. T. Watnik, and V. A. Cassella, “Efficient multibeam large-angle nonmechanical laser beam steering from computer-generated holograms rendered on a liquid crystal spatial light modulator,” Appl. Opt. 55(16), 4336–4341 (2016). [CrossRef]
12. S. Chung, H. Abediasl, and H. Hashemi, “A Monolithically Integrated Large-Scale Optical Phased Array in Silicon-on-Insulator CMOS,” IEEE J. Solid-State Circuits 53(1), 275–296 (2018). [CrossRef]
13. D. Inoue, T. Ichikawa, A. Kawasaki, and T. Yamashita, “Demonstration of a new optical scanner using silicon photonics integrated circuit,” Opt. Express 27(3), 2499–2508 (2019). [CrossRef]
14. C. Li, X. Cao, K. Wu, X. Li, and J. Chen, “Lens-based integrated 2D beam-steering device with defocusing approach and broadband pulse operation for Lidar application,” Opt. Express 27(23), 32970–32983 (2019). [CrossRef]
15. Y. C. Chang, M. C. Shin, C. T. Phare, S. A. Miller, E. Shim, and M. Lipson, “Metalens-enabled low-power solid-state 2D beam steering,” in Conference on Lasers and Electro-Optics, OSA Technical Digest (Optical Society of America, 2019), paper SF3N.5.
16. C. S. Im, S. M. Kim, K. P. Lee, S. H. Ju, J. H. Hong, S. W. Yoon, T. Kim, E. S. Lee, B. Bhandari, C. Zhou, S. Y. Ko, Y. H. Kim, M. C. Oh, and S. S. Lee, “Hybrid Integrated Silicon Nitride–Polymer Optical Phased Array for Efficient Light Detection and Ranging,” J. Lightwave Technol. 39(13), 4402–4409 (2021). [CrossRef]
17. S. M. Kim, E. S. Lee, K. W. Chun, J. Jin, and M. C. Oh, “Compact solid-state optical phased array beam scanners based on polymeric photonic integrated circuits,” Sci Rep 11(1), 10576 (2021). [CrossRef]
18. H. Ito, Y. Kusunoki, J. Maeda, D. Akiyama, N. Kodama, H. Abe, R. Tetsuya, and T. Baba, “Wide beam steering by slow-light waveguide gratings and a prism lens,” Optica 7(1), 47–52 (2020). [CrossRef]
19. W. B. Lee, C. S. Im, C. Zhou, B. Bhandari, D. Y. Choi, and S. S. Lee, “Metasurface doublet-integrated bidirectional grating antenna enabling enhanced wavelength-tuned beam steering,” Photon. Res. 10(1), 248–255 (2022). [CrossRef]
20. Y. C. Chang, M. C. Shin, C. T. Phare, S. A. Miller, E. Shim, and M. Lipson, “2D beam steerer based on metalens on silicon photonics,” Opt. Express 29(2), 854–864 (2021). [CrossRef]
21. C. Kim, S. J. Kim, and B. Lee, “Doublet metalens design for high numerical aperture and simultaneous correction of chromatic and monochromatic aberrations,” Opt. Express 28(12), 18059–18076 (2020). [CrossRef]
22. B. Groever, W. T. Chen, and F. Capasso, “Meta-Lens Doublet in the Visible Region,” Nano Lett. 17(8), 4902–4907 (2017). [CrossRef]
23. W. Liu, Z. Li, H. Cheng, C. Tang, J. Li, S. Zhang, S. Chen, and J. Tian, “Metasurface Enabled Wide-Angle Fourier Lens,” Adv. Mater. 30(23), 1706368 (2018). [CrossRef]
24. C. Li, X. Cao, K. Wu, G. Qiu, M. Cai, G. Zhang, X. Li, and J. Chen, “Blind zone-suppressed hybrid beam steering for solid-state Lidar,” Photon. Res. 9(9), 1871–1880 (2021). [CrossRef]
25. Y. Li, L. Ge, M. Chen, Z. Zhang, Z. Li, and J. Wang, “Multibeam 3-D-Printed Luneburg Lens Fed by Magnetoelectric Dipole Antennas for Millimeter-Wave MIMO Applications,” IEEE Trans. Antennas Propag. 67(5), 2923–2933 (2019). [CrossRef]
26. Q. Gao, S. Liverman, and A. X. Wang, “Design and Characterization of High Efficiency Nanoantenna Couplers with Plasmonic Integrated Circuit,” J. Lightwave Technol. 35(15), 3182–3188 (2017). [CrossRef]
27. F. F. Manzillo, A. Clemente, and J. L. González-Jiménez, “High-Gain D-Band Transmitarrays in Standard PCB Technology for Beyond-5G Communications,” IEEE Trans. Antennas Propag. 68(1), 587–592 (2020). [CrossRef]
28. Y. Ge, C. Lin, and Y. Liu, “Broadband Folded Transmitarray Antenna Based on an Ultrathin Transmission Polarizer,” IEEE Trans. Antennas Propag. 66(11), 5974–5981 (2018). [CrossRef]
29. M. I. Shalaev, J. Sun, A. Tsukernik, A. Pandey, K. Nikolskiy, and N. M. Litchinitser, “High-Efficiency All-Dielectric Metasurfaces for Ultracompact Beam Manipulation in Transmission Mode,” Nano Lett. 15(9), 6261–6266 (2015). [CrossRef]
30. Y. Guo, X. Ma, M. Pu, X. Li, Z. Zhao, and X. Luo, “High-Efficiency and Wide-Angle Beam Steering Based on Catenary Optical Fields in Ultrathin Metalens,” Adv. Opt. Mater. 6(19), 1800592 (2018). [CrossRef]
31. M. Pu, X. Li, Y. Guo, X. Ma, and X. Luo, “Nanoapertures with ordered rotations: symmetry transformation and wide-angle flat lensing,” Opt. Express 25(25), 31471–31477 (2017). [CrossRef]
32. C. Saeidi and D. van der Weide, “A figure of merit for focusing metasurfaces,” Appl. Phys. Lett. 106(11), 113110 (2015). [CrossRef]
33. G. B. Wu, Q. L. Zhang, K. F. Chan, B. J. Chen, and C. H. Chan, “Amplitude-Modulated Leaky-Wave Antennas,” IEEE Trans. Antennas Propag. 69(7), 3664–3676 (2021). [CrossRef]
34. G. Zhou, S. W. Qu, J. Wu, and S. Yang, “High-efficiency unidirectional vertical emitter achieved by an aperture-coupling nanoslot antenna array,” Opt. Express 29(16), 25399–25411 (2021). [CrossRef]
35. A. Yaacobi, E. Timurdogan, and M. R. Watts, “Vertical emitting aperture nanoantennas,” Opt. Lett. 37(9), 1454–1456 (2012). [CrossRef]
36. Y. S. Zeng, S. W. Qu, B. J. Chen, and C. H. Chan, “All-plasmonic Optical Phased Array Integrated on a Thin-film Platform,” Sci Rep 7(1), 9959 (2017). [CrossRef]
37. G. Bellanca, G. Calò, A. E. Kaplan, P. Bassi, and V. Petruzzelli, “Integrated Vivaldi plasmonic antenna for wireless on-chip optical communications,” Opt. Express 25(14), 16214–16227 (2017). [CrossRef]
38. R. Fatemi, P. P. Khial, A. Khachaturian, and A. Hajimiri, “Breaking FOV-Aperture Trade-Off with Multi-Mode Nano-Photonic Antennas,” IEEE J. Sel. Top. Quantum Electron. 27(1), 1–14 (2021). [CrossRef]
39. F. Aflatouni, B. Abiri, A. Rekhi, and A. Hajimiri, “Nanophotonic coherent imager,” Opt. Express 23(4), 5117–5125 (2015). [CrossRef]
40. T. J. Li, G. M. Wang, T. Cai, H. P. Li, J. G. Liang, and J. Lou, “Broadband Folded Transmitarray Antenna with Ultralow-Profile Based on Metasurfaces,” IEEE Trans. Antennas Propag. 69(10), 7017–7022 (2021). [CrossRef]
41. A. Yu, F. Yang, A. Z. Elsherbeni, J. Huang, and Y. Rahmat-Samii, “Aperture efficiency analysis of reflectarray antennas,” Microw. Opt. Technol. Lett. 52(2), 364–372 (2010). [CrossRef]
