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Device layout of CMOS color sensors based on anti-Hermitian metasurfaces a Top- and b side-view of color sensor device layout including electrical contacts. c Oblique view of scanning electron micrograph, just after nano patterning of PIN Si rods. d Side cross-section view and e top view of nanocylinder array, after SiO2 gap-filling and ITO electrode deposition. The white scale bar corresponds to 500 nm in c–e. The diagonal red line in c and e indicates the cross-section presented in d.
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The demand for essential pixel components with ever-decreasing size and enhanced performance is central to current optoelectronic applications, including imaging, sensing, photovoltaics and communications. The size of the pixels, however, are severely limited by the fundamental constraints of lightwave diffraction. Current development using transmi...
Citations
... Optical image sensors are increasingly gaining widespread use in diverse applications, including mobile devices, augmented reality glasses, and sensors for autonomous vehicles and robots. The demand for high-quality image sensors has driven rapid evolution in various aspects, such as increased image resolution [1]- [9], improved low-light imaging capabilities [10]- [12], and pixel miniaturization [13]- [15]. Currently, complementary metal-oxide-semiconductor (CMOS) image sensors (CIS) have mainly utilized silicon (Si)-based photodetectors with additional components, such as color filters [16], [17], microlenses, and antireflection coatings [18], to facilitate color separation and efficient light collection, as illustrated in Figure 1(a). ...
... Hence, recent research has aimed to reduce the overall thickness of devices by simultaneously integrating the functionalities of microlenses, color filters, antireflection coatings, and Si photodetectors into a single metasurface. For example, anti-Hermitian Si metasurface [13], [14], Si-Al hybrid nanoantennas [15], and filterfree image sensor pixels comprising Si nanowire [21] have been proposed as miniaturized CMOS-compatible image sensors. Additionally, advanced design like stacked silicon and germanium nanopillars [22] shows promise for the next generation of compact CMOS image sensors. ...
Silicon is the dominant material in complementary metal-oxide-semiconductor (CMOS) imaging devices because of its outstanding electrical and optical properties, well-established fabrication methods, and abundance in nature. However, with the ongoing trend toward electronic miniaturization, which demands smaller pixel sizes in CMOS image sensors, issues, such as crosstalk and reduced optical efficiency, have become critical. These problems stem from the intrinsic properties of Si, particularly its low absorption in the long wavelength range of the visible spectrum, which makes it difficult to devise effective solutions unless the material itself is changed. Recent advances in optical metasurfaces have offered new possibilities for solving these problems. In this study, we propose color arrestor pixels (CAPs) as a new class of color image sensors whose composite spectral responses directly mimic those of the human eye. The key idea is to employ linearly independent combinations of standardized color matching functions. These new basis functions allow our device to reproduce colors more accurately than the currently available image sensors with red-green-blue filters or other metasurface-based sensors, demonstrating an average CIEDE2000 color difference value of only 1.79 when evaluating 24 colors from the Gretag-Macbeth chart under standard illuminant D65. Owing to their high fidelity to the human eye response, CAPs consistently exhibit exceptional color reproduction accuracy under various spectral illumination compositions. With a small footprint of 860 nm height and 221 nm full-color pixel pitch, the CAPs demonstrated high absorption efficiencies of 79 %, 81 %, and 63 % at wavelengths of 452 nm, 544 nm, and 603 nm, respectively, and good angular tolerance. With such a high density of pixels efficiently capturing accurate colors, CAPs present a new direction for optical image sensor research and their applications.
... In particular, dielectric metasurfaces constructed from the subwavelength array of lossless nanomaterials have been used to develop practical optical applications, including optical elements and imaging devices. Research on developing lenses [1]- [9], color printing [10]- [12], and color filters [13]- [16] using nanoscaled structures has been extensively conducted, and metasurface-based devices such as polarimeters [17]- [20] and photodetectors [21]- [24] and ultrathin imaging elements [25], [26] have been demonstrated. Furthermore, to overcome the aforementioned limit on the loss of light in the CIS system, the concept of a nanophotonic color router has been proposed and intensively studied recently [27]- [35]. ...
CMOS image sensor (CIS) plays a crucial role in diverse optical applications by facilitating the capture of images in the visible and near-infrared spectra. The enhancement of image resolution in CIS by an increase in pixel density is becoming more significant and realizable with the recent progress of nanofabrication. However, as pixel size decreases towards the diffraction limit, there is an inevitable trade-off between the scale-down of pixel size and the enhancement of optical sensitivity. Recently, to overcome this, an entirely new concept of spectral sensing using a nanophotonic-based color router has been proposed. In this work, we present a metasurface-based spectral router to effectively split the spectrum from visible to near-infrared and redirect through the four optical channels to the targeted pixel surfaces. We optimize the metasurface that simultaneously controls the phases of the transmitted light of targeted spectra, i.e. red (R), green (G), blue (B), and near-infrared (NIR), which is the largest number of channels reported based on a single layered metasurface and has an optical efficiency that surpasses the efficiency of conventional color filter systems.
... Over the past decade, various photonic crystal slab filters, plasmonic and metasurface filters were also proposed to be integrated with CMOS camera chips (e.g., refs. [4][5][6]. It was believed that these thin film optical filters can be integrated with each pixel of the camera chip and enable various spectroscopy analysis functionalities, including miniaturized spectrometers (e.g., ref. 7), polarimetric sensing/imaging (e.g., ref. 8) and compressing spectroscopic sensing 9 . ...
Compact, lightweight, and on-chip spectrometers are required to develop portable and handheld sensing and analysis applications. However, the performance of these miniaturized systems is usually much lower than their benchtop laboratory counterparts due to oversimplified optical architectures. Here, we develop a compact plasmonic “rainbow” chip for rapid, accurate dual-functional spectroscopic sensing that can surpass conventional portable spectrometers under selected conditions. The nanostructure consists of one-dimensional or two-dimensional graded metallic gratings. By using a single image obtained by an ordinary camera, this compact system can accurately and precisely determine the spectroscopic and polarimetric information of the illumination spectrum. Assisted by suitably trained deep learning algorithms, we demonstrate the characterization of optical rotatory dispersion of glucose solutions at two-peak and three-peak narrowband illumination across the visible spectrum using just a single image. This system holds the potential for integration with smartphones and lab-on-a-chip systems to develop applications for in situ analysis.
... If the metal patterns of metasurfaces are etched on the silicon wafer by chemical vapor deposition or electroplating and connected with the field effect transistor manufactured by the CMOS technique, the structures of the metasurfaces can be changed and various functions can be realized by controlling the on-off states of the FETs. Another advantage of the CMOS technique is that even the circuits fabricated by the outdated 90 nm or 65 nm technique is still relatively small compared with the micron size in the terahertz band, so it is convenient to design multi-bit metasurface unit cells with this technique [258,259]. ...
Metasurfaces have shown their great capability to manipulate electromagnetic waves. As a new concept, reconfigurable metasurfaces attract researchers’ attention. There are many kinds of reconfigurable components, devices and materials that can be loaded on metasurfaces. When cooperating with reconfigurable structures, dynamic control of the responses of metasurfaces are realized under external excitations, offering new opportunities to manipulate electromagnetic waves dynamically. This review introduces some common methods to design reconfigurable metasurfaces classified by the techniques they use, such as special materials, semiconductor components and mechanical devices. Specifically, this review provides a comparison among all the methods mentioned and discusses their pros and cons. Finally, based on the unsolved problems in the designs and applications, the challenges and possible developments in the future are discussed.
... It may further realize the fully chip-integrated optical sensing and detecting functions and be readily integrated with numerous functionalities [10]. The silicon material device technology is established, affordable, and compatible with the CMOS process [38,39]. Thus, researchers' interest has been drawn to silicon-based high refractive index sensor chips. ...
Quasi-bound states in the continuum (quasi-BIC) in all-dielectric metasurfaces provide a crucial platform for sensing due to its ability to enhance strong matter interactions between light-waves and analytes. In this study, a novel high-sensitivity all-dielectric sensor composed of a periodic array of silicon (Si) plates with square nanoholes in the continuous near-infrared band is theoretically proposed. By adjusting the position of the square nanohole, the symmetry-protected BIC and Friedrich–Wintgen BIC (FW–BIC) can be excited. The torodial dipole (TD) and electric quadruple (EQ) are demonstrated to play a dominating role in the resonant modes by near-field analysis and multipole decomposition. The results show that the sensitivity, the Q-factor, and the corresponding figure of merit (FOM) can simultaneously reach 399 nm/RIU (RIU is refractive index unit), 4959, and 1281, respectively. Compared with other complex nanostructures, the proposed metasurface is more feasible and practical, which may open up an avenue for the development of ultrasensitive sensors.
... Nevertheless, this approach is generally limited in scalability and miniaturization. Alternatively, other CMOS compatible color sensor designs are based on p-i-n anti-Hermitian Si metasurface (34) or the aluminum (Al)-Si junction with a large pixel size of~10 μm (21). In addition, both designs (21,34) exhibit substantial dark current, which induces a large background signal for photodetection. ...
... Alternatively, other CMOS compatible color sensor designs are based on p-i-n anti-Hermitian Si metasurface (34) or the aluminum (Al)-Si junction with a large pixel size of~10 μm (21). In addition, both designs (21,34) exhibit substantial dark current, which induces a large background signal for photodetection. ...
Digital camera sensors use color filters on photodiodes to achieve color selectivity. As the color filters and photosensitive silicon layers are separate elements, these sensors suffer from optical cross-talk, which sets limits to the minimum pixel size. Here, we report hybrid silicon-aluminum nanostructures in the extreme limit of zero distance between color filters and sensors. This design could essentially achieve submicrometer pixel dimensions and minimize the optical cross-talk arising from tilt illuminations. The designed hybrid silicon-aluminum nanostructure has dual functionalities. Crucially, it supports a hybrid Mie-plasmon resonance of magnetic dipole to achieve color-selective light absorption, generating electron hole pairs. Simultaneously, the silicon-aluminum interface forms a Schottky barrier for charge separation and photodetection. This design potentially replaces the traditional dye-based filters for camera sensors at ultrahigh pixel densities with advanced functionalities in sensing polarization and directionality, and UV selectivity via interband plasmons of silicon.
... Metasurfaces composed of subwavelength antenna arrays promote the development of light optical devices 1 . The flourishing researches of metasurfaces have been extensively applicated in the field of waveplates 2,3 , holographic imaging [4][5][6][7] , optical information encryption 8,9 , and quantum communications [10][11][12] . In particular, metalenses, kinds of metasurfaces, have great application potential as a means to replace and surpass traditional optical lenses. ...
Metalenses as miniature flat lenses exhibit a substantial potential in replacing traditional optical component. Although the metalenses have been intensively explored, their functions are limited by poor active ability, narrow operating band and small depth of field (DOF). Here, we show a dielectric metalens consisting of TiO2 nanofins array with ultrahigh aspect ratio to realize active multiband varifocal function. Regulating the orbital angular momentum (OAM) by the phase assignment covering the 2π range, its focal lengths can be switched from 5 mm to 35 mm. This active optical multiplexing uses the physical properties of OAM channels to selectively address and decode the vortex beams. The multiband capability and large DOFs with conversion efficiency of 49% for this metalens are validated for both 532 nm and 633 nm, and the incidence wavelength can further change the focal lengths. This non-mechanical tunable metalens demonstrates the possibility of active varifocal metalenses.
... Nevertheless, this approach is generally limited by its potential scalability and miniaturization. Alternatively, other CMOS compatible color sensor designs are based on p-i-n anti-Hermitian Si metasurface 31 or the Al-Si junction with a large pixel size of ~10 µm. 19 In addition, both of these designs 19,31 exhibit significant dark current, which induces a large background signal for photodetection. ...
... Alternatively, other CMOS compatible color sensor designs are based on p-i-n anti-Hermitian Si metasurface 31 or the Al-Si junction with a large pixel size of ~10 µm. 19 In addition, both of these designs 19,31 exhibit significant dark current, which induces a large background signal for photodetection. ...
Digital camera sensors utilize color filters on photodiodes to achieve color selectivity. As color filters and photosensitive silicon layers are separate elements, these sensors suffer from optical cross-talk, which sets limits to the minimum pixel size. In this paper, we report hybrid silicon-aluminum nanostructures in the extreme limit of zero distance between color filters and sensors. This design could essentially achieve sub micron pixel dimensions and minimize the optical cross-talk originated from tilt illuminations. The designed hybrid silicon-aluminum nanostructure has dual functionalities. Crucially, it supports a hybrid Mie-plasmon resonance of magnetic dipole to achieve the color-selective light absorption, generating electron hole pairs. Simultaneously, the silicon-aluminum interface forms a Schottky barrier for charge separation and photodetection. This design could potentially replace the traditional dye based filters for camera sensors at ultra-high pixel densities with advanced functionalities in sensing polarization and directionality, as well as UV selectivity via interband plasmons of silicon.
... Zhang et al., further demonstrated sub-wavelength scale color pixels in a CMOS compatible platform based on Anti-Hermitian metasurfaces (Figure 7p) [60]. The AH Silicon metasurfaces, with two-dimensional arrays of three differently sized nanocylinders, are coupled with a shallow PIN junction for efficient carrier transport and electrical readout. ...
Photodetectors are the essential building blocks of a wide range of optical systems. Typical photodetectors only convert the intensity of light electrical output signals, leaving other electromagnetic parameters, such as the frequencies, phases, and polarization states unresolved. Metasurfaces are arrays of subwavelength structures that can manipulate the amplitude, phase, frequency, and polarization state of light. When combined with photodetectors, metasurfaces can enhance the light-matter interaction at the pixel level and also enable the detector pixels to resolve more electromagnetic parameters. In this paper, we review recent research efforts in merging metasurfaces with photodetectors towards improved detection performances and advanced detection schemes. The impacts of merging metasurfaces with photodetectors, on the architecture of optical systems, and potential applications are also discussed.
... Metallic nanostructures, such as 2D nanoholes and one-dimensional (1D) gratings, are well-known structures for implementing high-efficiency light control using SPPs, such as in extraordinary optical transmission (EOT) [38][39][40] and wavelength-selective perfect absorption/emission [41][42][43]. In addition, spectral filters using SPPs are highly promising for a wide range of applications, such as spectral imaging [44][45][46][47] and complementary metal oxide semiconductor sensors [48,49]. ...
Hexagonal boron nitride (hBN) exhibits natural hyperbolic dispersion in the infrared (IR) wavelength spectrum. In particular, the hybridization of its hyperbolic phonon polaritons (HPPs) and surface plasmon resonances (SPRs) induced by metallic nanostructures is expected to serve as a new platform for novel light manipulation. In this study, the transmission properties of embedded hBN in metallic one-dimensional (1D) nanoslits were theoretically investigated using a rigorous coupled wave analysis method. Extraordinary optical transmission (EOT) was observed in the type-II Reststrahlen band, which was attributed to the hybridization of HPPs in hBN and SPRs in 1D nanoslits. The calculated electric field distributions indicated that the unique Fabry–Pérot-like resonance was induced by the hybridization of HPPs and SPRs in an embedded hBN cavity. The trajectory of the confined light was a zigzag owing to the hyperbolicity of hBN, and its resonance number depended primarily on the aspect ratio of the 1D nanoslit. Such an EOT is also independent of the slit width and incident angle of light. These findings can not only assist in the development of improved strategies for the extreme confinement of IR light but may also be applied to ultrathin optical filters, advanced photodetectors, and optical devices.
