Aug 8, 2014
Low-cost printable photonic integrated devices
By directly printing devices onto a functional resist with a high refractive index, optical components can be created without the use of any etching steps. This new low-cost fabrication technique can produce printable integrated circuits, as reported by researchers at aBeam Technologies, the Molecular Foundry and NanoOptic Devices. Presenting in Nanotechnology, several optical components are demonstrated, including ridge waveguides, light splitters and digital planar holograms that operate in the visible wavelength range. The approach could revolutionize the development of integrated photonic devices.
Printable photonic chip. a) optical picture of a photonic chip, b) SEM picture of a planar hologram. c) Optical picture of an integrated chip excited with a red laser at the input.
The nanoimprint lithography (NIL) of functional materials is a powerful approach to develop low-cost photonic devices with high optical performance. Supported by the US Air Force STTR Program, researchers at aBeam Technologies, the Molecular Foundry (a DOE-funded user facility for nanoscience at Lawrence Berkeley National Laboratory) and NanoOptic Devices have collaborated. They demonstrate a novel approach to fabricate low-cost, printable photonic integrated devices that work in the visible wavelength range.
The devices are printed directly onto a functional NIL resist and their optical properties (transparency and refractive index) are tuned by post-annealing. “We wanted to simplify the fabrication of photonic devices as much as possible by printing them onto a functional material in one single step, thereby avoiding any etching steps,” says Christophe Peroz.
High refractive index
The method combines the advantages of top-down (NIL) and bottom-up (sol-gel chemistry) approaches. After annealing at high temperatures, the photonic structures shrink and reach a refractive index up to 2.1. “Conventional lithography is very challenging for high refractive index materials, particularly at few nanometer resolution, but now we have shown that it can be easy” said lead author Carlos Pina-Hernandez.
The printed structures on the top of a waveguide core are used to create planar lightwave circuits. To demonstrate the practicality of this process, elementary optical structures like multi-mode ridge waveguides, light splitters and more complex devices like digital planar holograms (DPH) are fabricated. Printable wavelength demultiplexer-on-chips were also created and their performance was comparable to current devices fabricated by standard and more expensive technologies.
Nanofabrication team. From left to right: Giuseppe Calafiore, Stefano Cabrini, Carlos Pina- Hernandez, Scott Dhuey, Christophe Peroz at The Molecular Foundry – LBNL. Picture by A. Schwartzberg.
The road is open
This work demonstrates the high potential of nanoimprint technology for fabricating novel photonic devices at low-cost and high throughput. According to the Molecular Foundry’s Stefano Cabrini, “Direct nanoimprinting of functional materials is just beginning and I have no doubt that a lot of applications will emerge in the near future.”
More information about the research can be found in the journal Nanotechnology.
About the author
The work was led by Christophe Peroz (aBeam Tech.) and Stefano Cabrini (Molecular Foundry) and performed at the Molecular Foundry, Lawrence Berkeley National Laboratory, in Berkeley, California. The Molecular Foundry is one of five United States Department of Energy (DOE) Nanoscale Science Research Centers, national user facilities for interdisciplinary research at the nanoscale, supported by the DOE Office of Science. The nanoimprint technology was developed by Carlos Pina Hernandez (aBeam Tech.), Scott Dhuey (Molecular Foundry) and Giuseppe Calafiore (aBeam Tech.). Optical characterization of the printed structures were carried out by Alexander Koshelev, Alexander Goltsov and Vladimir Yankov, at NanoOptic Devices.
Work at the Molecular Foundry was supported by the Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under contract no. DE-AC02- 05CH11231. The work is supported by the Air Force Office of Scientific Research (AFOSR), Air Force Material Command, USAF, under grant/contract number FA9550-14-C-0020 in the framework of a STTR project.