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Toward photonic–electronic convergence based on heterogeneous platform of merging lithium niobate into silicon

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The rapid development of fabrication techniques has boosted the resurgence of integrated photonics based on lithium niobate (LN). While thin-film LN is available and has been a promising photonic platform owing to its superior material properties, it is held back by its non-compatibility with complementary metal-oxide-semiconductor (CMOS) processes and the lack of high-density scaling possibilities. Silicon (Si), despite its less favorable intrinsic properties, was the dominant platform for photonic devices with compact footprints, high density, low cost, and high volume. By embedding thin-film LN into the Si platform, heterogeneous Si/LN photonic devices can be integrated on the same chip, simultaneously leveraging the advantages of the two different materials. In parallel with the development of photonic devices, research in photonic–electronic integrated circuits (PEICs) has flourished. This review begins with the material properties of LN and fabrication approaches for heterogeneous integration. We then introduce various photonic devices involving different functionalities. After that, the advances in photonic–electronic convergence are presented. Taking inspiration from PEICs using Si, we envision the contribution of thin-film LN conjunct with Si in the future PEICs. Finally, some conclusions and challenges are discussed.

© 2023 Optica Publishing Group

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Figures (8)

Fig. 1.
Fig. 1. Si/LNOI fabrication processes. Reprinted with permission from [58].
Fig. 2.
Fig. 2. Examples of thin-film LN-based MZMs. (a) Etched LN die bonded on patterned SOI waveguides. Reprinted by permission from Springer Nature: He et al., “High performance hybrid silicon and lithium niobate Mach–Zehnder modulators for 100 Gbits$^{-1}$ and beyond,” Nat. Photonics 13, 359–364 (2019) [60]. (b) The schematic of a SiN/LNOI modulator. Reprinted from [54]. (c) The schematic of a ${\rm{Si}}/{\rm{Si}}{{\rm{O}}_2}/{\rm{LNOI}}$ EOM. Reprinted from [84]. The Si waveguides are shrunk to push the light into the thin film of LN, and vice versa. (d) Etchless LN die bonded on patterned SOI waveguides. Reprinted from [79]. (e) The folded MZM on the etched LNOI platform using CL-TWEs. Reprinted from [91]. (f) The DPIQ modulator on the etched LNOI platform. Reprinted from [76].
Fig. 3.
Fig. 3. (a) Schematic of coupled microdisk and microring. Reprinted from [97]. (b) A laser comprises a pumping laser and a microring on the Er:LN platform. Reprinted from [101]. (c) Processes flow of an EO tunable laser based on the undoped LN platform and Er:LN platform. Reprinted from [102]. (d) Hybrid integrated laser structures with a LN cavity. Reprinted from [105]. (e) Schematic of a III-V-on-LN laser based on stacked layers. Reprinted with permission from Zhang et al., “Heterogeneous integration of III–V semiconductor lasers on thin-film lithium niobite platform by wafer bonding,” Appl. Phys. Lett. 122, 081103 (2023) [106]. Copyright 2023, AIP Publishing LLC.
Fig. 4.
Fig. 4. (a) A four-channel WDM device on the hybrid SRN/LNOI platform. Reprinted from [112]. (b) Illustration of a BIC-based mode (de)multiplexer. Reprinted from [90]. (c) Layout of the proposed reconfigurable two-mode (de)multiplexer. Reprinted from [113]. (d) Schematic of the PBS on etched LNOI. © 2022 IEEE. Reprinted, with permission, from Wu et al., “Lithium niobate thin film polarization beam splitter based on asymmetric directional coupling,” J. Lightwave Technol. 40, 7843–7847 (2022) [114].
Fig. 5.
Fig. 5. (a) Schematic of a chirped LN grating coupler with a metal mirror. Reprinted from [124]. (b) 2D LN grating coupler. Reprinted with permission from [125]. (c) Heterogeneous Si/LNOI grating coupler. Reprinted from [126]. (d) Bilayer inverse taper with the SiON cladding for the edge coupler. Reprinted from [127]. (e) Edge coupler with PLC. The cross view shows the mode distribution. Reprinted from Yang et al., “Efficient and scalable edge coupler based on silica planar light-wave circuits and lithium niobate thin films,” Opt. Laser Technol. 1363, 108867, copyright 2023, with permission from Elsevier [128].
Fig. 6.
Fig. 6. (a) Architecture of a photonic analog-to-digital converter system (reprinted from [169]) and (b) an optical computing system (reprinted from [174]). Both systems are comprised of MZMs, lasers, PDs, and electronic components including digital processor, control, etc.
Fig. 7.
Fig. 7. (a) Integrated photonic–electronic stack. © 2017 IEEE. Reprinted, with permission, from Berkly et al., “Electronic-photonic integrated circuit for 3D microimaging,” IEEE J. Solid-State Circuits 52, 161–172 (2017) [181]. (b) Co-packaged PEICs with a homodyne photodetector and an electronic TIA. Reprinted by permission from Springer Nature: Tasker et al., “Silicon photonics interfaced with integrated electronics for 9 GHz measurement of squeezed light,” Nat. Photonics 15, 11–15 (2021) [182]. (c) Co-packaged PEICs with a laser, Si photonic devices, and an electronic TIA. Reprinted from [183]. (d) Co-packaged PEICs with Si photonic devices and an electronic driver. Reprinted with permission from [184]. (e) SOI CMOS processes (reprinted with permission from [189], © The Optical Society) and (f) bulk Si CMOS processes cross section with relevant devices (reprinted by permission from Springer Nature: Atabaki et al., “Integrating photonics with silicon nano-electronics for the next generation of systems on a chip,” Nature 1479 556, 349–354 (2018) [190]).
Fig. 8.
Fig. 8. Vision of a hybrid PEIC merging thin-film LN with Si, III-V, Ge, and Au materials. The chip includes photonic and electronic components. The photonic components such as GC, EO MZM, EO PM, EO resonator, PD, spiral waveguide, and WDM are built in the Si/LNOI PICs. The III-V laser array is connected with Si/LNOI PICs through photonic wire bonds. While the electronic counterpart comprises digital/analog (D/A) converters, digital signal processor, buffer, microcontroller, and electronic driver.

Tables (5)

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Table 1. List of Key Properties of Some Materials that Are Commonly Used in Photonicsa

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Table 2. Representative EO MZMs Based on Monolithic and Heterogeneous LN Platformsa

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Table 3. Basic Information of Optically Pumped Lasers Based on the Er:LN Platform

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Table 4. Basic Information of Electrically Pumped Lasers Including Thin-Film LNa

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Table 5. Schemes and Performance of Off-Chip Couplers on the Different LN Platformsa

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