Research Bits: May 21

Photonics: Lithium tantalate PIC; programmable processor for RF; high-speed signal processing.


Lithium tantalate PICs

Researchers at EPFL and Shanghai Institute of Microsystem and Information Technology developed scalable photonic integrated circuits (PICs) based on lithium tantalate (LiTaO3). Lithium tantalate can provide excellent electro-optic qualities and is used in telecom 5G RF filters.

The team developed a wafer-bonding method for lithium tantalate, which is compatible with silicon-on-insulator production lines. They then masked the thin-film lithium tantalate wafer with diamond-like carbon and used DUV photolithography and dry-etching techniques to create optical waveguides, modulators, and ultra-high quality factor microresonators.

Using the method, they fabricated high-efficiency lithium tantalate PICs with an optical loss rate of 5.6 dB/m at telecom wavelength. They also built an electro-optic Mach-Zehnder modulator (MZM), used in high-speed optical fiber communication, that offers a half-wave voltage-length product of 1.9 V cm and an electro-optical bandwidth reaching 40 GHz.

“While maintaining highly efficient electro-optical performance, we also generated soliton microcomb on this platform,” said Chengli Wang, a post-doctoral researcher at EPFL, in a press release. “These soliton microcombs feature a large number of coherent frequencies and, when combined with electro-optic modulation capabilities, are particularly suitable for applications such as parallel coherent LiDAR and photonic computing.” [1]

Programmable processor for RF

Researchers from the Universitat Politècnica de València and the company iPRONICS built a multifunctional photonic chip for interconnecting the wireless and photonic segments of communication networks in telecommunications, data centers, AI infrastructure, and autonomous vehicles.

The photonic processor integrates a silicon photonic programmable core along with an electronic monitoring and controlling layer and a software layer for resource control and programming. It can provide the reconfigurable filtering, frequency conversion, arbitrary waveform generation, and beamforming functionality needed for 5/6 G wireless systems and typically provided by a microwave photonic subsystem.

“It can implement the twelve basic functionalities required by these systems and can be programmed on demand, thus increasing the efficiency of the circuit,” said José Capmany, a professor at UPV, in a statement. Next, the team plans to scale the chip for management of data flows in data centers and networks for AI systems. [2]

High-speed signal processing

Researchers from the City University of Hong Kong and Chinese University of Hong Kong built a microwave photonic chip based on a thin-film lithium niobate platform. The microwave photonics system combines ultrafast electro-optic conversion with low-loss, multifunctional signal processing on a single integrated chip. The team claims it is 1,000 times faster and consumes less energy than a traditional electronic processor.

“The chip can perform high-speed analog computation with ultrabroad processing bandwidths of 67 GHz and excellent computation accuracies,” said Feng Hanke, PhD student at CityUHK, in a statement. Applications include 5/6G wireless communication systems, high-resolution radar systems, artificial intelligence, computer vision, and image/video processing. [3]


[1] Wang, C., Li, Z., Riemensberger, J. et al. Lithium tantalate photonic integrated circuits for volume manufacturing. Nature (2024).

[2] Pérez-López, D., Gutierrez, A., Sánchez, D. et al. General-purpose programmable photonic processor for advanced radiofrequency applications. Nat Commun 15, 1563 (2024).

[3] Feng, H., Ge, T., Guo, X. et al. Integrated lithium niobate microwave photonic processing engine. Nature 627, 80–87 (2024).

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