Nanophotonics highlights Stanford meeting

The challenge for nanophotonics is not simply one of fabricating nanostructures, according to Frank Schellenberg, a strategic marketer for photolithography software at Mentor Graphics (San Jose, CA).

PALO ALTO, CA - The challenge for nanophotonics is not simply one of fabricating nanostructures, according to Frank Schellenberg, a strategic marketer for photolithography software at Mentor Graphics (San Jose, CA). Chemists have been creating nanostructures and dispensing them in beaker-sized quantities for some time. The challenge lies in positioning nanostructures where you want them and in having them do specific things.

Schellenberg made his comments during a nanophotonics panel discussion on the first day of the annual meeting of the Stanford Photonics Research Center. As usual, topics covered in the three-day multidisciplinary meeting ranged from the farthest reaches of fundamental optical sciences, such as quantum computing with linear optics, to everyday commercial realities, such as the technical challenges of meeting explosive consumer demand for cameras in cell phones.

So nanophotonics, a field in which fundamental enabling research continues at the same time as companies and products are beginning to appear on the market, seemed an apt topic choice for the annual industry panel session. Schellenberg, who sponsored several optical proximity correction (OPC) software startup companies while previously working at SEMATECH (Austin, Texas) and also directed the SEMATECH J111 OPC validation project, discussed the challenges of nanophotonics from the perspective of semiconductor lithography in which techniques such as OPC, phase-shifting masks and off-axis illumination enable the fabrication of circuit elements with feature sizes smaller than the wavelength of light they are written with.

Optical lithography manufacturing methods are not likely to extend much below 30-nm, despite the demand for even smaller components, he said. So the future of semiconductor manufacturing is likely to move toward hybrid fabrication methodology in which lithographic methods extend down to a threshold in the 30-nm region, and self-assembly of molecular or atomic-sized components builds upwards towards the lower limits of optical lithography.

Warren Packard, a managing director at Draper Fisher Jurvetson (Menlo Park, CA) discussed similar issues, but from the perspective of a venture capitalist who has begun to invest in startup nanotechnology companies. Packard characterized the transition to nanotechnology as a material shift from the current silicon “world” to a carbon or polymer material world, in which people envisage building things “atom by atom” but don’t necessarily appreciate the magnitude of the proposed task.

To place it in perspective, Packard pointed out that the number of molecules in just one drop of water (Avogadro’s number or 6x1023) dwarfs the total number of transistors ever made (on the order of 1019). So ultimately building products based on nanostructures will first require the development of a vertically integrated infrastructure similar to the one that has enabled and continues to enable the growth of electronics technology into an industry full of electronic products.

In a scientific presentation prior to the panel discussion, and again during the panel discussion, Harry Atwater, a professor of applied physics and materials science at California Institute of Technology (Pasadena, CA) discussed his work with subwavelength scale optoelectronic devices that enable spatial confinement of light at dimensions less than 10% of the free-space wavelength, as well as propagation around sharp corners and through nanoscale networks, by exploiting the dipole-dipole coupling at the plasmon frequency between nanoscale metal particles in particle chain arrays.

Resistive heating leads to relatively high losses during plamonic transmission but very small device dimensions enable design tradeoffs of localization versus loss, as researchers pursue performance goals that include transport of light on a chip over distances on the order of a centimeter, he said. Long-term goals include design of subwavelength-scale optoelectronic components such as waveguides, sources, detectors and modulators, as well as plasmonic gain components that Atwater calls “plasmonsters” and a recently developed FET-LED.

Of the four panelists, Stan Williams, a senior Hewlett-Packard (HP) Fellow and director of quantum science research at HP Labs (Palo Alto, CA), drew the lion’s share of audience question and commentary after he revealed the unfolding research and development strategy for nanophotonics at HP.

Williams said that during these years of rapid nanophotonic development, HP has been quietly building a research team and patent portfolio focused on technologies to exert quantum-level control over photons, and that he expects these ongoing efforts to yield an important source of intellectual property and royalty revenues to the company over the next 10 years. HP hopes that these nanophotonics moves will allow it to emulate successes achieved historically through a similar approach to molecular electronics. The proposed 10-year time frame is “too short for academics and too long for venture capitalists, but works for a big company,” Williams said.

- Hassaun A. Jones-Bey

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