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A wide-spectrum mid-infrared electro-optic intensity modulator employing a two-point coupled lithium niobate racetrack resonator
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- Authors
- Hyeon Hwang, Kiyoung Ko, Mohamad Reza Nurrahman, Kiwon Moon, Jung Jin Ju, Sang-Wook Han, Hojoong Jung, Min-Kyo Seo, Hansuek Lee
- Issue Date
- 2025-01
- Citation
- APL Photonics, v.10, pp.1-12
- ISSN
- 2378-0967
- Publisher
- American Institute of Physics
- Language
- English
- Type
- Journal Article
- Abstract
- Optical intensity modulators (OIMs) are essential for mid-infrared (mid-IR) photonics, enabling applications such as bond-selective molecular sensing, and free-space communications via atmospheric windows. Integrated photonics offers a compact and cost-effective solution, yet on-chip mid-IR OIMs significantly underperform compared to their near-IR counterparts. Furthermore, despite the potential benefits for system reconfiguration in accessing various communication frequencies and molecular absorption bands, developing a single OIM capable of operating across a broad spectral range remains a challenge. In this study, we introduce an on-chip OIM that operates over a wide wavelength range in the mid-IR, implemented using a racetrack resonator structure in thin film lithium niobate (TFLN). The modulator employs a two-point coupling scheme, allowing active control of the coupling strength to maintain critical coupling and thereby ensuring high modulation extinction across a wide spectral region. This approach not only achieves high modulation performance but also relaxes the design constraints and fabrication precision typically associated with resonator-based modulators, as confirmed through an analytic model. Implemented in TFLN having a wide transmission spectrum and strong electro-optic coefficient, the OIM demonstrates a modulation extinction ratio exceeding 20 dB with an electro-optic efficiency of 7.7 V cm over the wavelength range of 3.3-3.8 μm, which falls within the first atmospheric transmission widow in the mid-IR. This approach can be adapted to other spectral regions, providing a versatile solution for diverse photonic applications.
- KSP Keywords
- Absorption bands, Active control, Analytic model, Atmospheric transmission, Atmospheric windows, Coupling scheme, Design constraints, Electro-optic coefficient, Extinction Ratio(ER), Lithium niobate(LN), Mid-IR