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Realization of a wide steering end-fire facet optical phased array using silicon rich silicon nitride

https://doi.org/10.1364/OL.476819

Nejadriahi, Hani; Gaur, Prabhav; Johnson, Karl; Pappert, Steve; Fainman, Yeshaiahu; Yu, Paul (January 2023, Optics Letters)

The design, fabrication, and characterization of a 16-element optical phased array (OPA) using a high index (n = 3.1) silicon-rich silicon nitride (SRN) is demonstrated. We present one-dimensional beam steering with end-fire facet antennas over a wide steering range of >115° at a fixed wavelength of 1525 nm. A beam width of 6.3° has been measured at boresight, consistent with theory. We demonstrate SRN as a viable material choice for chip-scale OPA applications due to its high thermo-optic coefficient, high optical power handling capacity [negligible two-photon absorption (TPA)], wide transparency window, and CMOS compatibility.
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Efficient and compact thermo-optic phase shifter in silicon-rich silicon nitride

https://doi.org/10.1364/OL.431757

Nejadriahi, Hani; Pappert, Steve; Fainman, Yeshaiahu; Yu, Paul (September 2021, Optics Letters)

The design, fabrication, and characterization of low-loss ultra-compact bends in high-index ( $n = 3.1$ at $λ<#comment/> = 1550 n m$ ) plasma-enhanced chemical vapor deposition silicon-rich silicon nitride (SRN) were demonstrated and utilized to realize efficient, small footprint thermo-optic phase shifter. Compact bends were structured into a folded waveguide geometry to form a rectangular spiral within an area of $65 \times<#comment/> 65 µ<#comment/> m^{2}$ , having a total active waveguide length of 1.2 mm. The device featured a phase-shifting efficiency of $8 m W / π<#comment/>$ and a 3 dB switching bandwidth of 15 KHz. We propose SRN as a promising thermo-optic platform that combines the properties of silicon and stoichiometric silicon nitride.
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Thermo-optic properties of silicon-rich silicon nitride for on-chip applications

https://doi.org/10.1364/OE.396969

Nejadriahi, Hani; Friedman, Alex; Sharma, Rajat; Pappert, Steve; Fainman, Yeshaiahu; Yu, Paul (August 2020, Optics Express)

We demonstrate the thermo-optic properties of silicon-rich silicon nitride (SRN) films deposited using plasma-enhanced chemical vapor deposition (PECVD). Shifts in the spectral response of Mach-Zehnder interferometers (MZIs) as a function of temperature were used to characterize the thermo-optic coefficients of silicon nitride films with varying silicon contents. A clear relation is demonstrated between the silicon content and the exhibited thermo-optic coefficient in silicon nitride films, with the highest achievable coefficient being as high as (1.65±0.08) ×10⁻⁴K^-1. Furthermore, we realize an SRN multi-mode interferometer (MMI) based thermo-optic switch with over 20 dB extinction ratio and total power consumption for two-port switching of 50 mW.
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Programmable plasmonic phase modulation of free-space wavefronts at gigahertz rates

https://doi.org/10.1038/s41566-019-0360-3

Smolyaninov, Alexei; El Amili, Abdelkrim; Vallini, Felipe; Pappert, Steve; Fainman, Yeshaiahu (February 2019, Nature Photonics)

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