Abstract
We report, for the first time, on the design and experimental demonstration of fiber-chip surface grating couplers based on subwavelength grating engineered nanostructure operating in the low fiber chromatic dispersion window (around 1.3 μm wavelengths), which is of great interest for short-reach data communication applications. Our coupler designs meet the minimum feature size requirements of large-volume deep-ultraviolet stepper lithography processes. The fiber-chip couplers are implemented in a standard 220-nm-thick silicon-on-insulator (SOI) platform and are fabricated by using a single etch process. Several types of couplers are presented, specifically the uniform, the apodized, and the focusing designs. The measured peak coupling efficiency is -2.5 dB (56%) near the central wavelength of 1.3 μm. In addition, by utilizing the technique of the backside substrate metallization underneath the grating couplers, the coupling efficiency of up to -0.5 dB (89%) is predicted by Finite Difference Time Domain (FDTD) calculations.
Highlights
Silicon-on-insulator (SOI) is a compelling photonic platform for implementation of complex photonic functions and waveguide circuits on a compact optoelectronic chip [1,2]
We report, for the first time, on the design and experimental demonstration of fiber-chip surface grating couplers based on subwavelength grating engineered nanostructure operating in the low fiber chromatic dispersion window, which is of great interest for short-reach data communication applications
The fiber-chip couplers are implemented in a standard 220-nm-thick silicon-on-insulator (SOI) platform and are fabricated by using a single etch process
Summary
Silicon-on-insulator (SOI) is a compelling photonic platform for implementation of complex photonic functions and waveguide circuits on a compact optoelectronic chip [1,2]. A number of different implemenations of surface grating couplers have been reported with a steady progress in increasing the fiber-chip coupling efficiency, by optimizing the grating directionality and the field matching with the optical fiber mode. Short-reach datacom interconnects exhibit substantially relaxed loss requirements They can migrate from the telecommunications C-band (around 1.55 μm wavelengths), where the optical fiber exhibits very low loss, to the O-band (around 1.3 μm wavelengths) to beneficially exploit the zero-dispersion feature of standard single-mode optical fibers. We propose a comprehensive and general design procedure that enables the implementation of optimized subwavelength index engineered grating couplers with minimum feature sizes larger than 100 nm, compatible with large-volume fabrication processes like deep-ultraviolet stepper lithography. The coupler is advantageously implemented in a standard 220 nm SOI photonic platform and fabricated using a single-etch step process
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