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Two dimensional (2D) materials such as graphene and transition metal dichalcogenides (TMDs) are promising for optical modulation, detection, and light emission since their material properties can be tuned on-demand via electrostatic doping1–21. The optical properties of TMDs have been shown to change drastically with doping in the wavelength range near the excitonic resonances22–26. However, little is known about the effect of doping on the optical properties of TMDs away from these resonances, where the material is transparent and therefore could be leveraged in photonic circuits. Here, we probe the electro-optic response of monolayer TMDs at near infrared (NIR) wavelengths (i.e. deep in the transparency regime), by integrating them on silicon nitride (SiN) photonic structures to induce strong light -matter interaction with the monolayer. We dope the monolayer to carrier densities of (7.2 ± 0.8) × 1013 cm-2, by electrically gating the TMD using an ionic liquid [P14+] [FAP-]. We show strong electro-refractive response in monolayer tungsten disulphide (WS2) at NIR wavelengths by measuring a large change in the real part of refractive index ∆n = 0.53, with only a minimal change in the imaginary part ∆k = 0.004. We demonstrate photonic devices based on electrostatically gated SiN-WS2 phase modulator with high efficiency ( ) of 0.8 V · cm. We show that the induced phase change relative to the change in absorption (i.e. ∆n/∆k) is approximately 125, that is significantly higher than the ones achieved in 2D materials at different spectral ranges and in bulk materials, commonly employed for silicon photonic modulators such as Si and III-V on Si, while accompanied by negligible insertion loss. Efficient phase modulators are critical for enabling large-scale photonic systems for applications such as Light Detection and Ranging (LIDAR), phased arrays, optical switching, coherent optical communication and quantum and optical neural networks27–30.
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This content will become publicly available on December 1, 2027
Hybrid tungsten oxyselenide/graphene electrodes for near-lossless 2D semiconductor phase modulators
Abstract Optical phase modulators are critical components in integrated photonics, but conventional designs suffer from a trade-off between modulation efficiency and optical loss. Two-dimensional materials like graphene offer strong electro-optic effects, yet their high optical absorption at telecom wavelengths leads to significant insertion losses. Although monolayer transition metal dichalcogenides (TMDs) provide exceptional telecom-band transparency for low-loss electro-refractive response, their practical implementation in phase modulators requires top electrodes to enable vertical electric field tuning, which typically introduces parasitic absorption. Here, we address this challenge by developing hybrid tungsten oxyselenide/graphene (TOS/Gr) electrodes that minimize optical loss while enabling efficient phase modulation in TMD-based devices. The UV-ozone-converted TOS (from WSe2) acts as a heavy p-type dopant for graphene, making the graphene transparent in the NIR region while enhancing its conductivity. Our complete device integrates a hybrid TOS/graphene transparent electrode with a hexagonal boron nitride dielectric spacer and monolayer WS2electro-optic material on a SiN microring platform. This achieves a high modulation efficiency of 0.202 V·cm while maintaining an exceptionally low extinction ratio change of just 0.08 dB, demonstrating superior performance compared to modulators employing conventional electrodes. Our breakthrough in near-lossless phase modulation opens new possibilities for energy-efficient optical communications, photonic computing, and fault-tolerant quantum networks.
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- Award ID(s):
- 2309000
- PAR ID:
- 10695549
- Author(s) / Creator(s):
- ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; more »
- Publisher / Repository:
- Light: Science & Applications
- Date Published:
- Journal Name:
- Light: Science & Applications
- Volume:
- 15
- Issue:
- 1
- ISSN:
- 2047-7538
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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