New polymer materials make fabricating optical interconnects easier
New technology poised to make silicon photonics more practical, which
could boost efficiency of Internet data centers

Date:
April 13, 2022
Source:
Optica
Summary:
Researchers have developed new polymer materials that are ideal for
making the optical links necessary to connect chip-based photonic
components with board-level circuits or optical fibers. These
materials can be used to easily create interconnects between
photonic chips and optical printed circuit boards, the light-based
equivalent of electronic printed circuit boards.



FULL STORY ========================================================================== Researchers have developed new polymer materials that are ideal for
making the optical links necessary to connect chip-based photonic
components with board- level circuits or optical fibers. The polymers
can be used to easily create interconnects between photonic chips and
optical printed circuit boards, the light-based equivalent of electronic printed circuit boards.


========================================================================== "These new materials and the processes they enable could lead to powerful
new photonic modules based on silicon photonics," said research team
leader Robert Norwood from the University of Arizona. "They could
also be useful for optical sensing or making holographic displays
for augmented and virtual reality applications." Silicon photonics
technology allows light-based components to be integrated onto a tiny
chip. Although many of the basic building blocks of silicon photonic
devices have been demonstrated, better methods are needed to fabricate
the optical connections that link these components together to make more complex systems.

In the journal Optical Materials Express, the researchers report new
polymer materials that feature a refractive index that can be adjusted
with ultraviolet (UV) light and low optical losses. These materials
allow a single-mode optical interconnect to be printed directly into a
dry film material using a low cost, high throughput lithography system
that is compatible with the CMOS manufacturing techniques used to make chip-based photonic components.

"This technology makes it more practical to fabricate optical
interconnects, which can be used to make the Internet -- especially the
data centers that make it run -- more efficient," said Norwood. "Compared
to their electronic counterparts, optical interconnects can increase
data throughput while also generating less heat. This reduces power
consumption and cooling requirements." Replacing wires with light The
research expands on a vinylthiophenol polymer material system known as
S- BOC that the investigators developed previously. This material has
a refractive index that can be modified using UV illumination. In the
new work, the researchers partially fluorinated S-BOC to improve its
light efficiency. The new material system, called FS-BOC, exhibits lower optical propagation losses than many other optical interconnect materials.



========================================================================== "With this material we can use a process that we call SmartPrint to
directly write optical interconnections between different optical printed circuit board elements, such as ion-exchange (IOX) glass waveguides
provided by our collaborator Lars Brusberg from Corning Incorporated,"
said Norwood.

To perform the SmartPrint process, a FS-BOC film is applied directly
to a photonic component. No mechanical alignment is needed because
the optical interconnect is made using a maskless lithography system
that calculates where the interconnect is required by looking at the
components and then writing the optical interconnect into the polymer
using photoexposure. No additional processing is necessary other than
briefly heating the polymer film to 90 DEGC.

Because the fabrication approach is maskless, writing patterns can be
changed without making a new photomask.

Creating a connection To demonstrate the new materials, the researchers deposited them directly onto ion-exchange glass waveguide arrays, which
are commonly used for integrated photonic devices. They then printed
the coupling features needed to allow light to travel out of one IOX
waveguide, propagate into the newly fabricated polymer interconnect, and
then enter a second IOX waveguide adjacent to the initial IOX waveguide.

According to the researchers, the polymer optical interconnects worked
well and showed low propagation and coupling losses, which means very
little light was lost as it traveled within the interconnect or between
it and the other components.

The researchers are now working to improve the material's refractive index contrast and performance at high temperatures. "A higher refractive index contrast would make the material more tolerant to manufacturing variations while high temperature performance is likely needed for the interconnect
to withstand solder reflow processes, which take place above 200 DEGC,"
said Norwood.


========================================================================== Story Source: Materials provided by Optica. Note: Content may be edited
for style and length.


========================================================================== Journal Reference:
1. Julie I. Frish, Tristan S. Kleine, Roland Himmelhuber, Sasaan
Showghi,
Abhinav Nishant, Kyung-Jo Kim, Linan Jiang, Kaitlyn P. Martin,
Lars Brusberg, Stanley Pau, Thomas L. Koch, Jeffrey Pyun, Robert
A. Norwood.

Rapid photolithographic fabrication of high density optical
interconnects using refractive index contrast polymers. Optical
Materials Express, 2022; 12 (5): 1932 DOI: 10.1364/OME.454195 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/04/220413131210.htm

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