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New polymer materials make fabricating optical interconnects easier

New polymer materials make fabricating optical interconnects easier
New polymer materials make optical interface fabrication easier |  Newsletters

The researchers use what they call the SmartPrint process to develop new polymer materials. Credit: Robert Norwood, University of Arizona

Researchers have developed novel polymer materials that are ideal for making the optical connections needed to connect chip-based optical components to board-level circuits or optical fibers. Polymers can be used to easily create links between photonic chips and photovoltaic printed circuit boards, and are the light-based equivalent of printed circuit boards.

“These new materials and the processes that enable them can lead to powerful new photonic modules based on silicon photons,” said research team leader Robert Norwood of the University of Arizona. They can also be useful for visual sensing or for making 3D renderings for augmented and virtual reality applications.

Silicon photonic technology allows light-based components to be integrated into a small chip. Although many of the building blocks for silicon photonic devices have been demonstrated, better methods for fabricating the optical contacts that link these components together are needed to create more complex systems.

in the magazine Optical Express Material, researchers report novel polymer materials that feature a UV-modulated refractive index and low optical losses. These materials allow the single-mode optical junction to be printed directly into a dry film material using a low-cost, high-throughput lithography system compatible with CMOS fabrication techniques used to make chip-based optical components.

“This technology makes the fabrication of optical interfaces, which can be used to make the Internet – and especially the data centers that make it work – more efficient,” Norwood said. “Compared to their electronic counterparts, optical interfaces can increase data throughput while also generating less heat. This reduces power consumption and cooling requirements.”

Replacing wires with light

The research expands on the phenylthiophenol polymer system known as S-BOC that the researchers previously developed. This material has a refractive index that can be adjusted with UV illumination. In the new work, the researchers partially fluoresced S-BOC to improve its optical efficiency. The new material system, called FS-BOC, shows lower optical propagation losses than many other optical interconnection materials.

“With this material, we can use a process we call SmartPrint to write direct optical links between different elements of optical printed circuit boards, such as ion exchange (IOX) glass waveguides provided by our collaborator Lars Brusberg of Corning Incorporated,” Norwood said.

To perform the SmartPrint process, FS-BOC film is applied directly to an optical component. No mechanical alignment is required because the optical interconnection is done using a maskless lithographic system that calculates where the interconnection is located by looking at the components and then writing the optical interconnection into the polymer using exposure. No additional processing is necessary other than briefly heating the polymer film to 90°C. Since the manufacturing method is without a mask, the writing styles can be changed without making a new photomask.

Create a connection

To demonstrate the new materials, the researchers placed them directly on ion exchange glass waveguide arrays, which are commonly used for integrated photonic devices. They then print the coupling features needed to allow light to exit the IOX waveguide, diffuse into the newly synthesized polymer interconnection, and then introduce a second IOX waveguide adjacent to the initial IOX waveguide.

According to the researchers, the polymer photonic junctions worked well and showed low diffusion and coupling losses, which means very little light is lost as it travels within the interface or between it and other components.

The researchers are now working to improve their refractive index contrast and performance at high temperatures. “Higher refractive index anisotropy would make the material more tolerant to fabrication changes while higher temperature performance would likely be necessary for the interconnection to withstand solder reflow processes, which occur above 200°C,” Norwood said.

Ultra-compact optical device can lead to new optical technologies

more information:
Julie I. Frisch et al., Rapid lithographic fabrication of high-density optical junctions using refractive index contrast polymers, Optical Express Material (2022). doi: 10.1364/ome.454195

the quote: New Polymer Materials Make Optical Interconnects Easier (2022, Apr 13) Retrieved on Apr 13, 2022 from

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