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CUE 2004

ELECTRICAL AND COMPUTER ENGINEERING
Overcoming the Obstacles in Nanophotonics Manufacturing

Graduate student Wenjian Cai works on the alignment of a solid state pump laser used in 3D submicron machining of dielectric materials.

Nanoscience is one of the unexplored frontiers of science that offers the most exciting prospects for technological innovation. In particular, nanophotonics has a distinctive role to play because of the unique properties of photons as well as the established use of optics for data transmission and storage.

New materials called photonic crystals are showing promise for a revolution in photonics. Photonic crystals are structured materials that exhibit bandgaps permitting only certain wavelengths to propagate. A key aspect is the possibility of introducing defects that can control the propagation of light within very small volumes, which is a critical need for large-scale photonic integration.

Today, developing techniques for fabricating nanostructures inexpensively and in very large quantities is an area that requires substantial effort, yet nanoscience will not be fully successful until it has provided the base for manufacturing technologies that are economically viable. It is thus necessary to develop an entire new suite of manufacturing methods for nanostructures.

After a decade of intense theoretical research, photonics crystals have been created by various techniques. The most widely used approaches are nano-scale patterning of optical materials using lithographic techniques and self-assembly of nanoparticles. Nanolithography is well suited for the fabrication of planar structures on semiconductor materials such as silicon and gallium arsenide. While lithography can be extended to fabricate three-dimensional structures, it becomes extremely complex because it requires multiple processes of pattern generation, thin layer deposition, alignment, and pattern transfer. Issues such as processing time, tolerances, and cost still hinder its application. Conversely, self-assembly techniques use spontaneous crystallization of colloids to create periodic systems. Nanoparticle self-assembly provides a simple, cost-effective, and fast method for creating three-dimensional photonic crystals; however, self-assembled crystals become useful only after intentionally designed defects are introduced into the lattice, which is a problem that remains unresolved.

In an effort to address these issues, the National Science Foundation has recently awarded CU-Boulder a grant to develop fundamental processing methodologies for large-scale nanofabrication of photonic structures. The research team is led by Professor Rafael Piestun and includes professors Bart VanZeghbroeck, Wounjhang Park, and Steven George from the departments of Electrical and Computer Engineering and Chemical and Biological Engineering. To create a successful program, the CU team also has established partnerships with the National Institute of Standards and Technologies and with Agilent Technologies.

The new project is directed to overcome the main obstacles currently found in nanophotonics manufacturing: performance, scalability, and flexibility. The research team will address these needs by synergistically combining traditionally unrelated techniques to integrate dielectrics, metals, and semiconductors.

Fabricating photonic nanostructures in three dimensions opens a myriad of possibilities in science and technology. Chip-to-chip and on-chip optical interconnects could benefit because of the large number of interconnects that can be integrated on a single substrate. Long haul optical communication systems could integrate waveguides with sharp bends, directional couplers, add-drop filters, detectors, and sources. Micro-integrated optical sensors could be fabricated with this new process because it will be possible to integrate resonance filters and interferometers with silicon microelectronics. Smart parallel biosensors also can be envisioned where different optical channels perform different analyses on a sample placed on top of the integrated photonic circuit.

Scientists believe that nanophotonics will have an impact on areas such as communications and sensing similar to the impact semiconductors had on the microelectronics revolution.

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Student Profile: Brian Schwartz
As a child, Brian Schwartz was drawn to hands-on experiments with physical phenomena both in and out of the classroom, such as toying with balloon-propelled rockets or a magnifying glass on a sunny day. >> More