Ultra-compact lithium niobate photonic chip for high-capacity and energy-efficient wavelength-division-multiplexing transmitters

Recently,high-performance thin-film lithium niobate optical modulators have emerged that,together with advanced multiplexing technologies,are highly expected to satisfy the ever-growing demand for high-capacity optical interconnects utilizing multiple channels.Accordingly,in this study,a compact lithium-niobate-on-insulator(LNOI)photonic chip was adopted to establish four-channel wavelength-division-multiplexing(WDM)transmitters,comprising four optical modulators based on ultracompact 2×2 Fabry-Perot cavities and a four-channel WDM filter based on multimode waveguide gratings.The fabricated chip with four wavelength channels has a total footprint as compact as 0.3×2.8 mm^(2),and exhibits an excess loss of~0.8 dB as well as low inter-channel crosstalk of<–22 dB.Using this LNOI photonic chip,high-capacity data transmissions of 320 Gbps(4×80 Gbps)on-off-keying signals and 400 Gbps(4×100 Gbps)four-level pulse amplitude signals were successfully realized with the ultra-low power consumption of 11.9 fJ/bit.

High-speed 2D beam steering based on a thin-film lithium niobate optical phased array with a large field of view

An on-chip optical phased array (OPA) is considered as a promising solution for next generation solid-state beam steering.However,most of the reported OPAs suffer from low operating bandwidths,making them limited in many applications.We propose and demonstrate a high-speed 2D scanning OPA based on thin-film lithium niobate phase modulators with traveling-wave electrodes.The measured modulation bandwidth is up to 2.5 GHz.Moreover,an aperiodic array combined with a slab grating antenna is also used to suppress the grating lobes of far-field beams,which enables a large field of view (FOV) as well as small beam width.A 16-channel OPA demonstrates an FOV of 50°×8.6°and a beam width of 0.73°×2.8°in the phase tuning direction and the wavelength scanning direction,respectively.

Silicon photonics for high-capacity data communications

In recent years,optical modulators,photodetectors,(de)multiplexers,and heterogeneously integrated lasers based on silicon optical platforms have been verified.The performance of some devices even surpasses the traditional III-V and photonic integrated circuit(PIC)platforms,laying the foundation for large-scale photonic integration.Silicon photonic technology can overcome the limitations of traditional transceiver technology in high-speed transmission networks to support faster interconnection between data centers.In this article,we will review recent progress for silicon PICs.The first part gives an overview of recent achievements in silicon PICs.The second part introduces the silicon photonic building blocks,including low-loss waveguides,passive devices,modulators,photodetectors,heterogeneously integrated lasers,and so on.In the third part,the recent progress on high-capacity silicon photonic transceivers is discussed.In the fourth part,we give a review of high-capacity silicon photonic networks on chip.

Compact electro-optic modulator on lithium niobate

Fast electro-optic modulators with an ultracompact footprint and low power consumption are always highly desired for optical interconnects.Here we propose and demonstrate a high-performance lithium niobate electro-optic modulator based on a new 2×2 Fabry–Perot cavity.In this structure,the input and reflected beams are separated by introducing asymmetric multimode-waveguide gratings,enabling TE_(0)−TE_(1)mode conversion.The measured results indicate that the fabricated modulator features a low excess loss of∼0.9dB,a high extinction ratio of∼21dB,a compact footprint of∼2120μm^(2),and high modulation speeds of 40 Gbps OOK and 80 Gbps PAM4 signals.The demonstrated modulator is promising for high-speed data transmission and signal processing.