Subwavelength gratings engineered 90-degree optical hybrid for coherent detection

Minu Sunny; Winnie N. Ye

doi:10.1117/12.3001938

12 March 2024 Subwavelength gratings engineered 90-degree optical hybrid for coherent detection

Minu Sunny, Winnie N. Ye

Proceedings Volume 12889, Integrated Optics: Devices, Materials, and Technologies XXVIII; 128890G (2024) https://doi.org/10.1117/12.3001938
Event: SPIE OPTO, 2024, San Francisco, California, United States

Abstract

Coherent detection plays a major role in optical communications for data transfer. The data extraction is performed by acquiring phase, amplitude, and frequency information from an intermediate frequency signal generated by combining a low-power incoming optical signal with a high-power optical signal from a local oscillator laser with known phase and frequency. Heterodyne or balanced detection is the most popular method to convert the received optical signal into an electrical form due to several advantages over the homodyne technique including high receiver sensitivity, frequency selectivity, spectral efficiency, ease of data extraction, and good tolerance to fiber impairments. One of the key components in a heterodyne detection system is a 90- degree optical hybrid, which separates incoming signals into an in-phase and a quadrature component for coherent demodulation. Multimode Interferometers (MMIs), especially 2 x 4 MMIs, are usually employed to realize an optical hybrid due to their fabrication tolerance and passive nature. MMIs with subwavelength gratings (SWGs) can offer low loss and broad bandwidth in ultracompact size. In this study, we propose a 2 x 4 tapered MMI that operates at a center wavelength of 1550nm with SWGs on a silicon-on-insulator platform. The period of SWG is chosen as 215 nm and has a duty cycle of 0.55. We demonstrate an MMI with a total length of 57.91 μm, i.e multimode section of 34.62 μm long and width of 11.79 μm gradually increasing to 12.813 μm, while offering a broadband performance from 1450 nm to 1650nm with transmission power variations within ± 1 dB.

Conference Presentation

Citation Download Citation

Minu Sunny and Winnie N. Ye "Subwavelength gratings engineered 90-degree optical hybrid for coherent detection", Proc. SPIE 12889, Integrated Optics: Devices, Materials, and Technologies XXVIII, 128890G (12 March 2024); https://doi.org/10.1117/12.3001938

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