Photonic and Optical Devices

State of the evidence

The evidence establishes a strong trend toward increasing data capacity through Mode-Division Multiplexing (MDM), Wavelength-Division Multiplexing (WDM), and Polarization-Division Multiplexing (PDM) 1,3,5. Silicon photonics and Lithium Niobate on Insulator (LNOI) are the primary platforms for integrating these functions, with LNOI offering ultra-low propagation loss (0.4 dB/cm) 6. While high-speed chiplets and reconfigurable add-drop multiplexers (ROADMs) have been demonstrated 1,8, challenges remain in reducing inter-modal crosstalk and insertion losses 5,7. Fiber laser technology is well-matured across rare-earth doping and mode-locking for diverse industrial applications 4.

Key findings

• Integration of MDM and WDM on a silicon photonic chiplet can achieve 200G data rates within a 1.65 mm² footprint 1. 1
• LNOI platforms enable high-speed modulators and low-loss waveguides (0.4 dB/cm), bridging the gap between nonlinear properties and high-complexity circuits 6. 6
• Mode- and polarization-selective switches can route four data channels simultaneously with inter-modal crosstalk below -23.2 dB 5. 5
• Three-dimensional asymmetric waveguide branches allow for ultra-broadband mode multiplexers operating across the C+L band 7. 7
• Monolithically integrated ROADMs on silicon can freely add or drop mode channels using thermo-optic Mach-Zehnder switches 8. 8
• Rare-earth-doped fibers (Nd3+, Er3+) provide the basis for tunable, broadband, and Q-switched fiber lasers 4. 4

Where the evidence disagrees

• Trade-off between high-density integration (chiplets) and signal integrity (insertion loss and crosstalk) 1,5.
• LNOI offers superior material properties but has historically faced fabrication challenges regarding sidewall angles and loss, though recent results show significant improvement 6.

Open opportunities

What the research supports that no idea in the catalog takes yet.

• LNOI-based Quantum Photonic Integrated Circuit (QPIC) for low-loss state routing.

  P5 establishes ultra-low loss (0.4 dB/cm) in LNOI, which is critical for quantum states that cannot be amplified, yet no listed idea targets quantum routing.

• Ultra-broadband C+L band mode-selective interface for few-mode fiber networks.

  P6 demonstrates 3D asymmetric waveguides for C+L band operation with low crosstalk, but existing ideas focus on narrow-band chiplets rather than broadband network interfaces.

• Reconfigurable MDM-based Optical Neural Network (ONN) hardware.

  P2 explicitly mentions MDM's potential for complex optical neural networks, and P7 provides the mechanism for reconfigurable add-drop routing, but no idea implements an ONN.

References

1. 1.Chinese Optics Letters2026 · 1438 citations
2. 2.Best wavelet packet bases in a rate-distortion senseKannan Ramchandran, Martin Vetterli · 1993 · 679 citations
3. 3.Mode and Polarization‐Division Multiplexing Based on Silicon Nitride Loaded Lithium Niobate on Insulator PlatformXu Han, Yongheng Jiang, Andreas Frigg et al. · 2021 · 138 citations
4. 4.Rare-Earth-Doped Fiber Lasers and AmplifiersMichel J. F. Digonnet · 2026 · 814 citations
5. 5.On-chip silicon photonic 2 × 2 mode- and polarization-selective switch with low inter-modal crosstalkYong Zhang, Yu He, Qingming Zhu et al. · 2017 · 77 citations
6. 6.Ultra-low loss photonic circuits in lithium niobate on insulatorInna Krasnokutska, Jean-Luc Tambasco, Gordon Li (8558871) et al. · 2024 · 163 citations
7. 7.Ultra-broadband mode multiplexers based on three-dimensional asymmetric waveguide branchesYunfei Wu, Kin Seng Chiang · 2017 · 68 citations
8. 8.Monolithically integrated reconfigurable add-drop multiplexer for mode-division-multiplexing systemsShipeng Wang, Hao Wu, Hon Ki Tsang et al. · 2016 · 62 citations
9. 9.Engineering Non-Linear Decay Dynamics: Pulse-Level Control and Software-Defined Qubit Rescue on Superconducting ProcessorsK S, Unnikuttan · 2025 · 737 citations
10. 10.Proceedings of the American Mathematical SocietyExt A La, Yoneda Without, The Schanuel Lemma et al. · 2026 · 1257 citations