Abstract
1. INTRODUCTION
The advancement of nanofabrication, coupled with the attainment of a high level of complexity in photonic integrated circuits (PICs), triggered tremendous interest toward realizing miniaturized all-optical interconnects that are superior to electronic circuits in terms of bandwidth density, speed, and energy efficiency as well as mitigating the von Neumann data transmission bottleneck [1–3]. Particularly, the reconfigurable control of light propagating in PICs is crucially important for many emerging applications such as programmable PIC [4], neuro-inspired computing [5,6], quantum information processing [7,8], optical communication [9,10], microwave photonics [11], and sensor applications [12,13].
Reconfigurable photonic computing cores are conventionally implemented using waveguide meshes of Mach–Zehnder interferometers (MZIs) where the interference is controlled via two phase shifters that are independently tuned through volatile and weak modulation of the waveguide refractive index commonly using electro-optic or thermo-optic effects [4], leading to devices with a limited tunability, high energy consumption [several milliwatts (mW)], and large footprints [hundreds of micrometers (μm)] [14]. On the other hand, micro-ring resonators (MRRs) [15–20] and micro-electromechanical systems (MEMS) [21,22] offer high modulation depth and a relatively small footprint. Still, they suffer from a narrow operational bandwidth (less than 3 dB) [20], low tolerance to temperature variations and fabrication errors, as well as a large actuation voltage () [23]. Notably, systems based on exciting surface plasmon resonances (SPRs) enjoy the highest switching rates and smallest footprints. However, they suffer from high insertion and propagation losses as they require coupling from/to a photonic waveguide [24,25], and plasmonic metals are highly lossy [25], which hinder their widespread usage. The common volatility of these schemes necessitates an “always-on” power supply to retain the switching state, rendering them energy inefficient [14,26].
To circumvent these hurdles, phase-change materials (PCMs) emerged as candidates to demonstrate photonic reconfigurability owing to their unique tunable properties [27,28]. PCMs possess high contrasts in the electrical resistivity and refractive index between the resonant-bonded crystalline and covalent-bonded amorphous phase states over a wide spectral range. They are non-volatile, reversible, and they provide fast and low energy actuation ( [29]) by ultrashort electrical or optical pulses (up to subnanosecond) [30] and stable switching ability of more than cycles [31]. In addition, the scalability of PCMs makes their nanofabrication relatively approachable and compatible with other substrates, as their amorphous state is used during deposition [23]. Several PCM-based integrated photonic devices were recently demonstrated, e.g., photonic memories [32,33], optical modulators [34,35], optical switches [14–20], and optical computing [36,37]. In these applications, a top-cladding layer of (GST) and, recently, (GSST) was deposited onto a waveguide. However, the high absorption losses in one of the phases of such materials fundamentally restrict their use in phase modulation schemes for large-area PICs [4] and deep-neural networks [5,6], where light would propagate through several PCM-based interconnects. Although losses can be alleviated in devices working at the telecom wavelengths, this comes with the cost of sacrificing the device footprint. In addition, such approach is impractical at the visible and near-visible wavelengths due to the large intrinsic losses. Finally, the use of large-area PCMs creates a considerable barrier to the actuation mechanism (see Appendix A for more details).
Sign up for Photonics Research TOC. Get the latest issue of Photonics Research delivered right to you!Sign up now
On the other hand, optical metasurfaces enable unprecedented flexibility in controlling the propagation of light through a spatially dependent and abrupt phase change at an interface that is imposed by ultrathin artificial arrays of engineered subwavelength nanoantennas [38]. Metasurfaces have realized a plethora of ultracompact, broadband, and efficient on-chip photonic devices, such as mode converters [39], polarization rotators [39], mode-pass polarizers [40], power splitters [41], asymmetric power transmitters [39], second-harmonic generators [42], remote near-field controllers [43], and guided waves to free space wave couplers [44–46]. However, these devices are passive and application specific because the optical properties of the constitutional meta-atoms are permanent once fabricated. To actively tune the optical properties of metasurfaces, several approaches have been introduced [47,48] with considerable interest in using PCMs [28,49] due to their advantages as discussed above. So far, such investigations on reconfigurable metasurfaces are focusing on controlling light propagating in free space, e.g., for bichromatic and multifocus Fresnel zone plates [50], beam steering [31], tunable color generators [51], dynamic spectrum controllers [52], switchable spectral filters [53], information processing [54], communication [55], imaging [56], hologram and augmented reality [57–59], vortex beam generators, and illusion and cloaking [60].
In this paper, we extend the concept of reconfigurable metasurfaces to PICs by reporting a novel dynamic near-visible nanophotonic () switch enabled by combining two nanorod arrays of and a novel ultralow-loss PCM (antimony trisulfide ) superimposed on silicon nitride waveguide. Our designed device provides unprecedented functionality as it facilitates the non-volatile dynamic routing of light inside a multimode waveguide toward predefined outputs. The device shows a wide bandwidth of 22.6 THz, low loss (), and low cross talk () with a compact active length (5.5 μm). To the extent of our knowledge, our design enjoys a record footprint compared to PCM-based optical switches, which would overcome the challenges associated with large-area PCM actuation. Table 1 compares the design principles, the type of PCM designs, and performance of the reported () PCM-based switches and of our metasurface PCM-based switch. Appendix B discusses the need for visible/near-visible PICs. Comparison of Previously Reported PCM-Based (Design Principle PCM Design Bandwidth (THz) Cross Talk (dB) Operating Wavelength Range Reference Directional coupler GST layer 3.74 IR [ Directional coupler GSST layer 4.4 IR [ Contra-directional coupler GST-Si grating 0.275 IR [ Micro-ring resonator GST layer 0.125 IR [ Micro-ring resonator GST layer 0.125 IR [ Micro-ring resonator GST layer 0.125 IR [ Micro-ring resonator GST layer 0.125 IR [ Micro-ring resonator GST nanodisk 0.125 IR [ Micro-ring resonator GST layer 0.125 IR [ Micro-ring resonator 0.125 NA Visible [
2. MATERIALS AND METHODS
Figure 1(a) schematically illustrates the structure and functionality of our device, which is a Y-branch waveguide with a metasurface located on the surface of its stem. From bottom to top, the waveguide is formed by a silicon substrate, a 3 μm thick layer, and a ridge SiN waveguide. The metasurface consists of two sets of nanorods. Each set includes 28 equally spaced nanorods with a length and a center-to-center distance between neighbor nanorods . These two sets are aligned to form two adjacent rectangles separated by a gap . The total footprint of the metasurface is .
Figure 1.Design of the proposed metasurface-based reconfigurable (
The materials are chosen to realize a device appropriate for near-visible integrated photonics. The SiN waveguide has the advantages of thermodynamic stability, wide spectral range of transparency (), higher fabrication flexibility, and lower propagation losses compared to silicon waveguides [64]. The materials of the two sets of nanorods are chosen as PCM antimony trisulfide () for one set and amorphous titanium dioxide () for the other. Compared to the prototypical PCM (GST), the new class of PCM () has a bandgap tunable from 2.0 eV (crystalline) to 1.7 eV (amorphous), and thus it works in the near-visible spectrum with a low absorption coefficient and a relatively higher contrast in the change of the real part of its refractive index [65–67]. is chosen because it is lossless in the near-visible range and enjoys a high refractive index to provide strong guided light–nanorod interaction [68]. The top middle inset in Fig. 1(a) shows the reversible optical switching of the from the crystalline to amorphous phases. The optical switching [65–67] can be done using a 630 nm laser source with a power of up to 90 mW. This laser source provides stable performance and cycling durability of during the experiment [67]. The reversible switching between both structural states of is realized by controlling the width and focus of the laser pulse [67]. The crystallization process requires pulses with long time duration (100 ms) [67] to reach the glass transition temperature at 270°C [67]. In contrast, the re-amorphization process requires pulses with shorter time duration (400 ns) [67] to reach the melting temperature at 527.85°C [67] and then quickly cool it at a rate [53,67,69].
In our designed metasurface, the nanorod antennas cause a spatial linear phase shift of the optical mode in the waveguide in addition to the propagation phase along the propagation direction ( axis). The accumulative local phase shifts from the two nanorod sets result in a constructive interference that focuses the input fundamental mode in the stem multimode waveguide. Following that, the focused input mode partially converts the input fundamental mode to higher-order modes, creating an effective asymmetric multimode interferometer (MMI). Consequently, an image of the input mode is formed at the end of the stem multimode waveguide due to the self-imaging principle of the MMI [70]. The produced image is then routed in one of the predefined output ports depending on the phase of the PCM nanorods (specifically depending on the effective refractive index of the nanorod arrays). Therefore, when is in the crystalline state, it has a significantly higher effective index, causing a larger phase delay at the side where the PCM nanorods are located. In contrast, when the is in the amorphous state, the causes a larger phase delay at the other side of the waveguide, leading to the field constructively interfering at the opposite side.
The optical properties of the device were simulated using the finite-difference time-domain method (FDTD, Mode Solutions, Lumerical Ansys Inc.). The simulation domain was enclosed by eight standard perfectly matched layers as boundary conditions. To minimize the numerical dispersion and to enhance the interfaces’ resolution, we chose the nonuniform auto mesh setting with a minimum size of conformal mesh cell of 2.5 nm. The fundamental TE mode was launched into the stem SiN waveguide using a broadband mode source and enabling multifrequency calculations. The frequency-domain time power monitors were used to record the profile of the normalized electric field intensity, transmission at output ports, reflection, and scattering. For calculating the effective indices as well as the dispersion in the SiN waveguide, the finite-difference eigenmodes solver (FDE, Mode Solutions, Lumerical Ansys Inc.) was used. To estimate the effective indices of metasurface nanorod arrays, the effective medium theory was considered by using Rytov’s approximations.
To optimize the device performance, the ridge SiN multimode waveguide is chosen to have a rectangular shape with a height , a thickness of under-etched layer , and a sufficiently large width to support the multimode interference and to reduce the cross talk between the output ports [70] [see Fig. 1(b)]. Note that the two output waveguides are narrower to match the spot size of the produced single self-images and optimize the device cross talk. The mode of the output waveguides can be coupled with other devices with arbitrary widths using techniques such as waveguide tapers [71–74] or integrated mode size converters [75–77]. Appendix C shows the dependence of effective refractive indices and dispersion of modes on the width of the SiN waveguide. The two output ports have a width and are attached to the end of the stem waveguide at a position where the self-image is formed. During the simulation, the complex optical constants of SiN, , Si, and are obtained from the database of Palik [78], while the experimental values of are taken from Refs. [67,79]. Figures 1(c) and 1(d) list the optical constants of , SiN, and two phases of . To compromise between the absorption coefficient (k) and the refractive index contrast (), the operating bandwidth is set around 800 nm as shown in the red bars in Figs. 1(c) and 1(d).
The performance metrics of a waveguide optical switch are the cross talk and the transmission, where the former is defined as the contrast transmission ratio between the two output ports [14]. Although it is not easy to define a qualitative quantity for the performance metric, an efficient optical switch should exhibit low cross talk and high transmission. The metasurface was engineered adopting the direct design approach [80]. To obtain the target performance, first, the width () and height () of nanorods were fixed at (, ) to support Mie resonant modes in the nanoantennas [39,42,81,82] and to meet the current state of manufacturing capacity [65,66]. The period () was set at 200 nm to avoid diffraction effects [83,84]. Following that, the dimensions of -nanorods (width and height) were optimized to realize the desired optical routing response (see Appendix D for further details). The gap width () between the two nanorod sets was kept at 180 nm to bring about degrees of freedom to the metasurface fabrication. Finally, , , , and were parametrically swept in sequential order as shown in Figs. 2(a)–2(d). The final dimensions of the metasurface are as follows: the TiO2 nanorods have a width of 72 nm and a thickness of 250 nm; , , , and , indicating an ultracompact footprint (Fig. 2, inset). The suggested fabrication method and working setup of the proposed device are provided in Appendix E.
Figure 2.Metasurface parametric sweep. (a)–(d) Device cross talk as a function of metasurface footprint (
3. RESULTS AND DISCUSSION
Before presenting the functionality of the metasurface, it is instructive to characterize how the single metasurface nanoantenna confines the light inside the waveguide. Figures 3(a) and 3(b) show the calculated field distribution ( components) and the electric field intensity distribution in the nanorods and for both phases of . In our design, the dimensions of the nanorods are larger than those of the nanorods in order to increase the magnitude of phase delay (i.e., effective refractive index) and compensate for its lower refractive index compared to . Therefore, for , the field is mostly confined in the nanorod. When the PCM changes its state to , the field becomes strongly confined in the rods. Figure 3(c) shows the length dependence of the calculated effective refractive index for different nanorod antennas positioned on the SiN substrate at . The FDE method was implemented to obtain the effective refractive indices caused by metasurface nanoantennas. A significant difference is obtained between and antennas due to their high refractive index contrast. The of lies between the of and , which in turn partly explains the switching functionality of our device. Appendix F discusses the method used for calculating the equivalent effective indices of the and nanorod arrays. These results show that employing high-index dielectric/PCM nanoantennas on a waveguide offers a unique ability to independently and dynamically tune the localization of guided light by engineering the relative effective indices induced by the metasurface nanoantennas.
Figure 3.Characterization of nanoantenna structure. (a) Profile (
Figure 4(a) shows the normalized electric field intensity profile in the switch for at a wavelength 800 nm in the xy plane, when the fundamental TE mode is launched from the stem multimode waveguide to the Y branches along the propagation direction ( axis). In this case, the field is localized in the nanoantennas as shown in the enlarged view of the inset of Fig. 4(a); the result is consistent with Fig. 3(a), where TiO2 nanorods show stronger confinement than a-Sb2S3 nanorods. Figure 4(b) shows the calculated transmission spectra from to and from to . The average simulated insertion loss in the target port is . The insertion losses are caused mainly by the reflected optical power resulting from the impedance mismatch with the metasurface nanoantennas and the scattering losses are due to the strong light–antenna interactions at subwavelength intervals. The average value of the cross talk is found to be throughout the operating bandwidth.
Figure 4.Simulated device performance for
To further characterize the device performance, Fig. 4(c) shows the spectra of total transmission (T, ), reflection (R), and scattering (S) over the simulated wavelength region.
Figures 4(d)–4(f) show the functionality of the switch for . In this case, the field is localized in the nanorods because of its stronger light confinement than TiO2 nanorods [see Fig. 3(b)]. From the calculated transmission spectra in Fig. 4(e), the average value of cross talk is throughout the operating bandwidth. The average calculated insertion loss is , which is lower than the efficiency when the switch is in the . The higher insertion losses are due to increased reflection and scattering losses are because of the higher refractive index of compared to . Figure 4(f) shows the spectra of total transmission (T, ), reflection (R), and scattering (S) over the simulated wavelength region. We note that the produced modes at and maintain the polarization of the input mode and do not experience any polarization rotation (see Fig. 12 in Appendix G).
4. CONCLUSION
In conclusion, we have proposed a conceptually novel approach for devices that dynamically control guided light using a reconfigurable metasurface. We have demonstrated a broadband compact and low-loss () switch for near-visible wavelengths by integrating a metasurface consisting of two nanorod arrays of and on a silicon nitride waveguide. Our demonstrated device enjoys a record high bandwidth (22.6 THz) compared to other phase-change-material-based switches while having low loss (), low cross talk (), and ultracompact active length (5.5 μm). The proposed device could be a reliable component in the meshes of future energy-efficient large-scale PICs. Moreover, we believe that integrating active metasurfaces with photonic waveguides, as demonstrated in our example, may provide a step change toward realizing several tunable, efficient, and non-volatile chip-scale devices for applications in neuromorphic computing [5,6], quantum information processing [7,8], optical communication [9,10], microwave photonics [11], and biomedical sensing [12,13].
Acknowledgment
Acknowledgment. A. A. acknowledges the CAS-TWAS Presidents Fellowship Program. M. E. initiated the project and conceived the approach. C. G., W. L., M. E., and J. C. supervised the project. A. A. designed the metasurface and performed simulations. A. A., M. E., W. L., J. C., and G. V. analyzed the data. C. S. contributed to the discussions. A. A. wrote the paper with input from all the authors. All authors discussed the research.
APPENDIX A: THE DRAWBACKS OF USING LARGE-AREA PCMs FOR DEVICES’ ACTUATION MECHANISMS
The use of large-area PCMs creates a considerable barrier to the actuation mechanism because of the following reasons: first, the lack of optimization for additional scaling and integration because of the inaccurate, slow, and diffraction-limited alignment process [
A practical solution is reducing the PCMs’ volume to the subwavelength scale [
APPENDIX B: THE NEED FOR VISIBLE/NEAR-VISIBLE PHOTONIC INTEGRATED DEVICES
The PCM-based integrated devices reported thus far are restricted to the infrared region, where the silicon waveguide exhibits optical transparency and where the PCM (GST and GSST) shows low absorption and high [
APPENDIX C: THE DESIGN OF A STEM MULTIMODE WAVEGUIDE
To study the MMI effect that takes place in our SiN waveguide, it is vital to check the properties of the supported modes in the waveguide. Therefore, in Mode Solutions (Lumerical Ansys Inc), the FDE method was used to calculate the dependence of stem waveguide width () on the effective refractive index () and of different modes as shown in Figs.
Figure 5.Multimode waveguide characterization. The dependence of waveguide width on the (a)
APPENDIX D: THE ROLE OF OPTIMIZING THE HEIGHT AND WIDTH OF TiO2 IN THE DEVICE PERFORMANCE
To justify the selected dimensions for , in Fig.
Figure 6.Parametric sweep of
Figure 7.Full-wave simulation showing the optical field intensity
APPENDIX E: THE SUGGESTED FABRICATION METHOD AND EXPERIMENTAL SETUP OF RECONFIGURABLE METASURFACE-BASED (1×2) WAVEGUIDE SWITCH
The fabrication of nanorod arrays on top of nanophotonic waveguides was previously described by Yu
Figure 8.Suggested fabrication method employing three steps of electron beam lithography: (a) two positive resists followed by LPCVD to transfer the desired patterns of the nanorod arrays onto the developed gaps and (b) a negative resist followed by reactive ion etching (RIE) to define the SiN waveguide.
Figure 9.Device fabrication tolerance. (a) and (b) Simulated device cross talk for the fundamental mode operating at
Figure 10.Schematic illustration of the experimental setup suggested for characterizing the performance of the proposed reconfigurable switch. Here, PPG is a programmable pulse generator, PC is a power controller, and M is a mirror.
APPENDIX F: THE EFFECTIVE INDICES OF A NANOROD-ARRAY-LOADED SiN WAVEGUIDE
The effective refractive indices of each nanorod array in our metasurface were calculated using Rytov’s approximation [
The effective indices of nanorod arrays in the amorphous () and crystalline () states can be given by
The effective index of a nanorod array can be described as
Figures
Figure 11.Sketches showing
Figure 12.Modes in the input and output ports of SiN waveguides. Simulated
APPENDIX G: MODAL PROFILES AT THE DEVICE INPUT AND OUTPUT PORTS
It is important to note that the produced modes at the output ports of the device maintain the polarization of the input TE00 mode in both Sb2S3 phases. Figure
References
[1] B. J. Shastri, A. N. Tait, T. Ferreira de Lima, W. H. P. Pernice, H. Bhaskaran, C. D. Wright, P. R. Prucnal. Photonics for artificial intelligence and neuromorphic computing. Nat. Photonics, 15, 102-114(2021).
[2] Z. Chen, M. Segev. Highlighting photonics: looking into the next decade. eLight, 1, 2(2021).
[3] G. Wetzstein, A. Ozcan, S. Gigan, S. Fan, D. Englund, M. Soljačić, C. Denz, D. A. B. Miller, D. Psaltis. Inference in artificial intelligence with deep optics and photonics. Nature, 588, 39-47(2020).
[4] W. Bogaerts, D. Pérez, J. Capmany, D. A. B. Miller, J. Poon, D. Englund, F. Morichetti, A. Melloni. Programmable photonic circuits. Nature, 586, 207-216(2020).
[5] J. Feldmann, N. Youngblood, C. D. Wright, H. Bhaskaran, W. H. P. Pernice. All-optical spiking neurosynaptic networks with self-learning capabilities. Nature, 569, 208-214(2019).
[6] J. Torrejon, M. Riou, F. A. Araujo, S. Tsunegi, G. Khalsa, D. Querlioz, P. Bortolotti, V. Cros, K. Yakushiji, A. Fukushima, H. Kubota, S. Yuasa, M. D. Stiles, J. Grollier. Neuromorphic computing with nanoscale spintronic oscillators. Nature, 547, 428-431(2017).
[7] J. Wang, F. Sciarrino, A. Laing, M. G. Thompson. Integrated photonic quantum technologies. Nat. Photonics, 14, 273-284(2020).
[8] A. Blais, S. M. Girvin, W. D. Oliver. Quantum information processing and quantum optics with circuit quantum electrodynamics. Nat. Phys., 16, 247-256(2020).
[9] S. Leedumrongwatthanakun, L. Innocenti, H. Defienne, T. Juffmann, A. Ferraro, M. Paternostro, S. Gigan. Programmable linear quantum networks with a multimode fibre. Nat. Photonics, 14, 139-142(2020).
[10] Q. Ma, L. Chen, H. B. Jing, Q. R. Hong, H. Y. Cui, Y. Liu, L. Li, T. J. Cui. Controllable and programmable nonreciprocity based on detachable digital coding metasurface. Adv. Opt. Mater., 7, 1901285(2019).
[11] D. Marpaung, J. Yao, J. Capmany. Integrated microwave photonics. Nat. Photonics, 13, 80-90(2019).
[12] Y. Wang, W. Li, M. Li, S. Zhao, F. De Ferrari, M. Liscidini, F. G. Omenetto. Biomaterial-based ‘structured opals’ with programmable combination of diffractive optical elements and photonic bandgap effects. Adv. Mater., 31, 1805312(2019).
[13] Z. Li, J. Zou, H. Zhu, B. T. T. Nguyen, Y. Shi, P. Y. Liu, R. C. Bailey, J. Zhou, H. Wang, Z. Yang, Y. Jin, P. H. Yap, H. Cai, Y. Hao, A. Q. Liu. Biotoxoid photonic sensors with temperature insensitivity using a cascade of ring resonator and Mach–Zehnder interferometer. ACS Sens., 5, 2448-2456(2020).
[14] P. Xu, J. Zheng, J. K. Doylend, A. Majumdar. Low-loss and broadband nonvolatile phase-change directional coupler switches. ACS Photon., 6, 553-557(2019).
[15] M. Rudé, J. Pello, R. E. Simpson, J. Osmond, G. Roelkens, J. J. G. M. van der Tol, V. Pruneri. Optical switching at 1.55 μm in silicon racetrack resonators using phase change materials. Appl. Phys. Lett., 103, 141119(2013).
[16] M. Stegmaier, C. Ríos, H. Bhaskaran, C. D. Wright, W. H. P. Pernice. Nonvolatile all-optical 1 × 2 switch for chipscale photonic networks. Adv. Opt. Mater., 5, 1600346(2017).
[17] J. Zheng, A. Khanolkar, P. Xu, S. Colburn, S. Deshmukh, J. Myers, J. Frantz, E. Pop, J. Hendrickson, J. Doylend, N. Boechler, A. Majumdar. GST-on-silicon hybrid nanophotonic integrated circuits: a non-volatile quasi-continuously reprogrammable platform. Opt. Mater. Express, 8, 1551-1561(2018).
[18] Y. Zhang, J. B. Chou, J. Li, H. Li, Q. Du, A. Yadav, S. Zhou, M. Y. Shalaginov, Z. Fang, H. Zhong, C. Roberts, P. Robinson, B. Bohlin, C. Ríos, H. Lin, M. Kang, T. Gu, J. Warner, V. Liberman, K. Richardson, J. Hu. Broadband transparent optical phase change materials for high-performance nonvolatile photonics. Nat. Commun., 10, 4279(2019).
[19] C. Wu, H. Yu, H. Li, X. Zhang, I. Takeuchi, M. Li. Low-loss integrated photonic switch using subwavelength patterned phase change material. ACS Photon., 6, 87-92(2019).
[20] C. Zhang, M. Zhang, Y. Xie, Y. Shi, R. Kumar, R. R. Panepucci, D. Dai. Wavelength-selective 2 × 2 optical switch based on a Ge2Sb2Te5-assisted microring. Photon. Res., 8, 1171-1176(2020).
[21] T. J. Seok, N. Quack, S. Han, R. S. Muller, M. C. Wu. Large-scale broadband digital silicon photonic switches with vertical adiabatic couplers. Optica, 3, 64-70(2016).
[22] T. J. Seok, J. Luo, Z. Huang, K. Kwon, J. Henriksson, J. Jacobs, L. Ochikubo, R. S. Muller, M. C. Wu. Silicon photonic wavelength cross-connect with integrated MEMS switching. APL Photon., 4, 100803(2019).
[23] J. Zheng, S. Zhu, P. Xu, S. Dunham, A. Majumdar. Modeling electrical switching of nonvolatile phase-change integrated nanophotonic structures with graphene heaters. ACS Appl. Mater. Interfaces, 12, 21827-21836(2020).
[24] M. Ono, M. Hata, M. Tsunekawa, K. Nozaki, H. Sumikura, H. Chiba, M. Notomi. Ultrafast and energy-efficient all-optical switching with graphene-loaded deep-subwavelength plasmonic waveguides. Nat. Photonics, 14, 37-43(2020).
[25] M. Thomaschewski, V. A. Zenin, C. Wolff, S. I. Bozhevolnyi. Plasmonic monolithic lithium niobate directional coupler switches. Nat. Commun., 11, 748(2020).
[26] D. Pérez, I. Gasulla, P. Das Mahapatra, J. Capmany. Principles, fundamentals, and applications of programmable integrated photonics. Adv. Opt. Photon., 12, 709-786(2020).
[27] M. Wuttig, H. Bhaskaran, T. Taubner. Phase-change materials for non-volatile photonic applications. Nat. Photonics, 11, 465-476(2017).
[28] S. Abdollahramezani, O. Hemmatyar, H. Taghinejad, A. Krasnok, Y. Kiarashinejad, M. Zandehshahvar, A. Alù, A. Adibi. Tunable nanophotonics enabled by chalcogenide phase-change materials. Nanophotonics, 9, 1189-1241(2020).
[29] N. Farmakidis, N. Youngblood, X. Li, J. Tan, J. L. Swett, Z. Cheng, C. D. Wright, W. H. P. Pernice, H. Bhaskaran. Plasmonic nanogap enhanced phase-change devices with dual electrical-optical functionality. Sci. Adv., 5, eaaw2687(2019).
[30] D. Loke, T. H. Lee, W. J. Wang, L. P. Shi, R. Zhao, Y. C. Yeo, T. C. Chong, S. R. Elliott. Breaking the speed limits of phase-change memory. Science, 336, 1566(2012).
[31] C. R. de Galarreta, A. M. Alexeev, Y.-Y. Au, M. Lopez-Garcia, M. Klemm, M. Cryan, J. Bertolotti, C. D. Wright. Nonvolatile reconfigurable phase-change metadevices for beam steering in the near infrared. Adv. Funct. Mater., 28, 1704993(2018).
[32] C. Rios, P. Hosseini, C. D. Wright, H. Bhaskaran, W. H. P. Pernice. On-chip photonic memory elements employing phase-change materials. Adv. Mater., 26, 1372-1377(2014).
[33] Z. Cheng, C. Ríos, N. Youngblood, C. D. Wright, W. H. P. Pernice, H. Bhaskaran. Device-level photonic memories and logic applications using phase-change materials. Adv. Mater., 30, 1802435(2018).
[34] M. A. Kats, D. Sharma, J. Lin, P. Genevet, R. Blanchard, Z. Yang, M. M. Qazilbash, D. N. Basov, S. Ramanathan, F. Capasso. Ultra-thin perfect absorber employing a tunable phase change material. Appl. Phys. Lett., 101, 221101(2012).
[35] H. Liang, R. Soref, J. Mu, A. Majumdar, X. Li, W.-P. Huang. Simulations of silicon-on-insulator channel-waveguide electrooptical 2 × 2 switches and 1 × 1 modulators using a Ge2Sb2Te5 self-holding layer. J. Lightwave Technol., 33, 1805-1813(2015).
[36] J. Feldmann, M. Stegmaier, N. Gruhler, C. Ríos, H. Bhaskaran, C. D. Wright, W. H. P. Pernice. Calculating with light using a chip-scale all-optical abacus. Nat. Commun., 8, 1256(2017).
[37] M. Xu, X. Mai, J. Lin, W. Zhang, Y. Li, Y. He, H. Tong, X. Hou, P. Zhou, X. Miao. Recent advances on neuromorphic devices based on chalcogenide phase-change materials. Adv. Funct. Mater., 30, 2003419(2020).
[38] A. H. Dorrah, N. A. Rubin, A. Zaidi, M. Tamagnone, F. Capasso. Metasurface optics for on-demand polarization transformations along the optical path. Nat. Photonics, 15, 287-296(2021).
[39] Z. Li, M.-H. Kim, C. Wang, Z. Han, S. Shrestha, A. C. Overvig, M. Lu, A. Stein, A. M. Agarwal, M. Lončar, N. Yu. Controlling propagation and coupling of waveguide modes using phase-gradient metasurfaces. Nat. Nanotechnol., 12, 675-683(2017).
[40] B. Wang, S. Blaize, R. Salas-Montiel. Nanoscale plasmonic TM-pass polarizer integrated on silicon photonics. Nanoscale, 11, 20685-20692(2019).
[41] A. Alquliah, M. Elkabbash, J. Zhang, J. Cheng, C. Guo. Ultrabroadband, compact, polarization independent and efficient metasurface-based power splitter on lithium niobate waveguides. Opt. Express, 29, 8160-8170(2021).
[42] C. Wang, Z. Li, M.-H. Kim, X. Xiong, X.-F. Ren, G.-C. Guo, N. Yu, M. Lončar. Metasurface-assisted phase-matching-free second harmonic generation in lithium niobate waveguides. Nat. Commun., 8, 2098(2017).
[43] V. Ginis, M. Piccardo, M. Tamagnone, J. Lu, M. Qiu, S. Kheifets, F. Capasso. Remote structuring of near-field landscapes. Science, 369, 436-440(2020).
[44] X. Guo, Y. Ding, X. Chen, Y. Duan, X. Ni. Molding free-space light with guided wave–driven metasurfaces. Sci. Adv., 6, eabb4142(2020).
[45] R. Guo, M. Decker, F. Setzpfandt, X. Gai, D.-Y. Choi, R. Kiselev, A. Chipouline, I. Staude, T. Pertsch, D. N. Neshev, Y. S. Kivshar. High–bit rate ultra-compact light routing with mode-selective on-chip nanoantennas. Sci. Adv., 3, e1700007(2017).
[46] S. Sun, Q. He, S. Xiao, Q. Xu, X. Li, L. Zhou. Gradient-index meta-surfaces as a bridge linking propagating waves and surface waves. Nat. Mater., 11, 426-431(2012).
[47] A. M. Shaltout, V. M. Shalaev, M. L. Brongersma. Spatiotemporal light control with active metasurfaces. Science, 364, eaat3100(2019).
[48] O. Tsilipakos, A. C. Tasolamprou, A. Pitilakis, F. Liu, X. Wang, M. S. Mirmoosa, D. C. Tzarouchis, S. Abadal, H. Taghvaee, C. Liaskos, A. Tsioliaridou, J. Georgiou, A. Cabellos-Aparicio, E. Alarcón, S. Ioannidis, A. Pitsillides, I. F. Akyildiz, N. V. Kantartzis, E. N. Economou, C. M. Soukoulis, M. Kafesaki, S. Tretyakov. Toward intelligent metasurfaces: the progress from globally tunable metasurfaces to software-defined metasurfaces with an embedded network of controllers. Adv. Opt. Mater., 8, 2000783(2020).
[49] F. Ding, Y. Yang, S. I. Bozhevolnyi. Dynamic metasurfaces using phase-change chalcogenides. Adv. Opt. Mater., 7, 1801709(2019).
[50] Q. Wang, E. T. F. Rogers, B. Gholipour, C.-M. Wang, G. Yuan, J. Teng, N. I. Zheludev. Optically reconfigurable metasurfaces and photonic devices based on phase change materials. Nat. Photonics, 10, 60-65(2016).
[51] S. G.-C. Carrillo, L. Trimby, Y.-Y. Au, V. K. Nagareddy, G. Rodriguez-Hernandez, P. Hosseini, C. Ríos, H. Bhaskaran, C. D. Wright. A nonvolatile phase-change metamaterial color display. Adv. Opt. Mater., 7, 1801782(2019).
[52] Z. Zhu, P. G. Evans, R. F. Haglund, J. G. Valentine. Dynamically reconfigurable metadevice employing nanostructured phase-change materials. Nano Lett., 17, 4881-4885(2017).
[53] C. Ruiz de Galarreta, I. Sinev, A. M. Alexeev, P. Trofimov, K. Ladutenko, S. G.-C. Carrillo, E. Gemo, A. Baldycheva, J. Bertolotti, C. D. Wright. Reconfigurable multilevel control of hybrid all-dielectric phase-change metasurfaces. Optica, 7, 476-484(2020).
[54] T. J. Cui, M. Q. Qi, X. Wan, J. Zhao, Q. Cheng. Coding metamaterials, digital metamaterials and programmable metamaterials. Light Sci. Appl., 3, e218(2014).
[55] L. Zhang, M. Z. Chen, W. Tang, J. Y. Dai, L. Miao, X. Y. Zhou, S. Jin, Q. Cheng, T. J. Cui. A wireless communication scheme based on space- and frequency-division multiplexing using digital metasurfaces. Nat. Electron., 4, 218-227(2021).
[56] L. Li, Y. Shuang, Q. Ma, H. Li, H. Zhao, M. Wei, C. Liu, C. Hao, C.-W. Qiu, T. J. Cui. Intelligent metasurface imager and recognizer. Light Sci. Appl., 8, 97(2019).
[57] R.-B. Hwang. Binary meta-hologram for a reconfigurable holographic metamaterial antenna. Sci. Rep., 10, 8586(2020).
[58] C. Liu, W. M. Yu, Q. Ma, L. Li, T. J. Cui. Intelligent coding metasurface holograms by physics-assisted unsupervised generative adversarial network. Photon. Res., 9, B159-B167(2021).
[59] J. Xiong, S.-T. Wu. Planar liquid crystal polarization optics for augmented reality and virtual reality: from fundamentals to applications. eLight, 1, 3(2021).
[60] X. G. Zhang, W. X. Jiang, H. L. Jiang, Q. Wang, H. W. Tian, L. Bai, Z. J. Luo, S. Sun, Y. Luo, C.-W. Qiu, T. J. Cui. An optically driven digital metasurface for programming electromagnetic functions. Nat. Electron., 3, 165-171(2020).
[61] Q. Zhang, Y. Zhang, J. Li, R. Soref, T. Gu, J. Hu. Broadband nonvolatile photonic switching based on optical phase change materials: beyond the classical figure-of-merit. Opt. Lett., 43, 94-97(2018).
[62] H. Hu, H. Zhang, L. Zhou, J. Xu, L. Lu, J. Chen, B. M. A. Rahman. Contra-directional switching enabled by Si-GST grating. Opt. Express, 28, 1574-1584(2020).
[63] Z. Fang, J. Zheng, A. Saxena, J. Whitehead, Y. Chen, A. Majumdar. Non-volatile reconfigurable integrated photonics enabled by broadband low-loss phase change material. Adv. Opt. Mater., 9, 2002049(2021).
[64] X. Li, N. Youngblood, Z. Cheng, S. G.-C. Carrillo, E. Gemo, W. H. P. Pernice, C. D. Wright, H. Bhaskaran. Experimental investigation of silicon and silicon nitride platforms for phase-change photonic in-memory computing. Optica, 7, 218-225(2020).
[65] W. Dong, H. Liu, J. K. Behera, L. Lu, R. J. H. Ng, K. V. Sreekanth, X. Zhou, J. K. W. Yang, R. E. Simpson. Wide bandgap phase change material tuned visible photonics. Adv. Funct. Mater., 29, 1806181(2019).
[66] K. V. Sreekanth, Q. Ouyang, S. Sreejith, S. Zeng, W. Lishu, E. Ilker, W. Dong, M. ElKabbash, Y. Ting, C. T. Lim, M. Hinczewski, G. Strangi, K.-T. Yong, R. E. Simpson, R. Singh. Phase-change-material-based low-loss visible-frequency hyperbolic metamaterials for ultrasensitive label-free biosensing. Adv. Opt. Mater., 7, 1900081(2019).
[67] M. Delaney, I. Zeimpekis, D. Lawson, D. W. Hewak, O. L. Muskens. A new family of ultralow loss reversible phase-change materials for photonic integrated circuits: Sb2S3 and Sb2Se3. Adv. Funct. Mater., 30, 2002447(2020).
[68] W. Zhu, R. Yang, G. Geng, Y. Fan, X. Guo, P. Li, Q. Fu, F. Zhang, C. Gu, J. Li. Titanium dioxide metasurface manipulating high-efficiency and broadband photonic spin Hall effect in visible regime. Nanophotonics, 9, 4327-4335(2020).
[69] M. Wuttig, N. Yamada. Phase-change materials for rewriteable data storage. Nat. Mater., 6, 824-832(2007).
[70] K. R. Safronov, D. N. Gulkin, I. M. Antropov, K. A. Abrashitova, V. O. Bessonov, A. A. Fedyanin. Multimode interference of Bloch surface electromagnetic waves. ACS Nano, 14, 10428-10437(2020).
[71] P. Sethi, A. Haldar, S. K. Selvaraja. Ultra-compact low-loss broadband waveguide taper in silicon-on-insulator. Opt. Express, 25, 10196-10203(2017).
[72] Y. Fu, T. Ye, W. Tang, T. Chu. Efficient adiabatic silicon-on-insulator waveguide taper. Photon. Res., 2, A41-A44(2014).
[73] J. Zhang, J. Yang, H. Xin, J. Huang, D. Chen, Z. Zhaojian. Ultrashort and efficient adiabatic waveguide taper based on thin flat focusing lenses. Opt. Express, 25, 19894-19903(2017).
[74] C. Sun, Y. Yu, X. Zhang. Ultra-compact waveguide crossing for a mode-division multiplexing optical network. Opt. Lett., 42, 4913-4916(2017).
[75] Y. Zhang, Y. He, H. Wang, L. Sun, Y. Su. Ultra-broadband mode size converter using on-chip metamaterial-based Luneburg lens. ACS Photon., 8, 202-208(2021).
[76] J. M. Luque-González, R. Halir, J. G. Wangüemert-Pérez, J. de-Oliva-Rubio, J. H. Schmid, P. Cheben, Í. Molina-Fernández, A. Ortega-Moñux. An ultracompact GRIN-lens-based spot size converter using subwavelength grating metamaterials. Laser Photon. Rev., 13, 1900172(2019).
[77] C. Yao, S. C. Singh, M. ElKabbash, J. Zhang, H. Lu, C. Guo. Quasi-rhombus metasurfaces as multimode interference couplers for controlling the propagation of modes in dielectric-loaded waveguides. Opt. Lett., 44, 1654-1657(2019).
[78] E. D. Palik. Handbook of Optical Constants of Solids(2012).
[79] M. Delaney, I. Zeimpekis, D. Lawson, D. Hewak, O. Muskens. A new family of ultra-low loss reversible phase change materials for photonic integrated circuits: Sb2S3 and Sb2Se3. Adv. Funct. Mater., 30, 2002447(2020).
[80] M. M. R. Elsawy, S. Lanteri, R. Duvigneau, J. A. Fan, P. Genevet. Numerical optimization methods for metasurfaces. Laser Photon. Rev., 14, 1900445(2020).
[81] K. Koshelev, Y. Kivshar. Dielectric resonant metaphotonics. ACS Photon., 8, 102-112(2021).
[82] I. Staude, T. Pertsch, Y. S. Kivshar. All-dielectric resonant meta-optics lightens up. ACS Photon., 6, 802-814(2019).
[83] R. Halir, P. J. Bock, P. Cheben, A. Ortega-Moñux, C. Alonso-Ramos, J. H. Schmid, J. Lapointe, D.-X. Xu, J. G. Wangüemert-Pérez, Í. Molina-Fernández, S. Janz. Waveguide sub-wavelength structures: a review of principles and applications. Laser Photon. Rev., 9, 25-49(2015).
[84] P. Cheben, R. Halir, J. H. Schmid, H. A. Atwater, D. R. Smith. Subwavelength integrated photonics. Nature, 560, 565-572(2018).
[85] J. Zheng, Z. Fang, C. Wu, S. Zhu, P. Xu, J. K. Doylend, S. Deshmukh, E. Pop, S. Dunham, M. Li, A. Majumdar. Nonvolatile electrically reconfigurable integrated photonic switch enabled by a silicon PIN diode heater. Adv. Mater., 32, 2001218(2020).
[86] Y. Zhang, C. Ríos, M. Y. Shalaginov, M. Li, A. Majumdar, T. Gu, J. Hu. Myths and truths about optical phase change materials: a perspective. Appl. Phys. Lett., 118, 210501(2021).
[87] K. Shportko, S. Kremers, M. Woda, D. Lencer, J. Robertson, M. Wuttig. Resonant bonding in crystalline phase-change materials. Nat. Mater., 7, 653-658(2008).
[88] Y. Wang, P. Landreman, D. Schoen, K. Okabe, A. Marshall, U. Celano, H. S. P. Wong, J. Park, M. L. Brongersma. Electrical tuning of phase-change antennas and metasurfaces. Nat. Nanotechnol., 16, 667-672(2021).
[89] Y. Zhang, C. Fowler, J. Liang, B. Azhar, M. Y. Shalaginov, S. Deckoff-Jones, S. An, J. B. Chou, C. M. Roberts, V. Liberman, M. Kang, C. Ríos, K. A. Richardson, C. Rivero-Baleine, T. Gu, H. Zhang, J. Hu. Electrically reconfigurable non-volatile metasurface using low-loss optical phase-change material. Nat. Nanotechnol., 16, 661-666(2021).
[90] T. Akiyama, M. Uno, H. Kitaura, K. Narumi, R. Kojima, K. Nishiuchi, N. Yamada. Rewritable dual-layer phase-change optical disk utilizing a blue-violet laser. Jpn. J. Appl. Phys., 40, 1598-1603(2001).
[91] W. Zhang, R. Mazzarello, M. Wuttig, E. Ma. Designing crystallization in phase-change materials for universal memory and neuro-inspired computing. Nat. Rev. Mater., 4, 150-168(2019).
[92] C. R. De Galarreta Fanjul. Reconfigurable phase-change optical metasurfaces: novel design concepts to practicable devices(2020).
[93] P. Trofimov, A. P. Pushkarev, I. S. Sinev, V. V. Fedorov, S. Bruyère, A. Bolshakov, I. S. Mukhin, S. V. Makarov. Perovskite–gallium phosphide platform for reconfigurable visible-light nanophotonic chip. ACS Nano, 14, 8126-8134(2020).
[94] B. Desiatov, A. Shams-Ansari, M. Zhang, C. Wang, M. Lončar. Ultra-low-loss integrated visible photonics using thin-film lithium niobate. Optica, 6, 380-384(2019).
[95] H. M. Mbonde, H. C. Frankis, J. D. B. Bradley. Enhanced nonlinearity and engineered anomalous dispersion in TeO2-coated Si3N4 waveguides. IEEE Photon. J., 12, 2200210(2020).
[96] H. El Dirani, L. Youssef, C. Petit-Etienne, S. Kerdiles, P. Grosse, C. Monat, E. Pargon, C. Sciancalepore. Ultralow-loss tightly confining Si3N4 waveguides and high-
[97] R. R. Grote, L. C. Bassett. Single-mode optical waveguides on native high-refractive-index substrates. APL Photon., 1, 071302(2016).
[98] K. Bi, Q. Wang, J. Xu, L. Chen, C. Lan, M. Lei. All-dielectric metamaterial fabrication techniques. Adv. Opt. Mater., 9, 2001474(2021).
[99] S. Rytov. Electromagnetic properties of a finely stratified medium. J. Exp. Theor. Phys., 2, 466-475(1956).
Set citation alerts for the article
Please enter your email address