Optical Metamaterials


At Phoebus Optoelectronics, my work took a turn from the academic to the intensely applied. Funded by SBIR Phase I and II grants, the company had a full understanding of the technical assets it had available, and was in search of markets for the technology it had developed. As a fabrication engineer, I was tasked with quickly prototyping test structures for prospective products, and evaluating the feasibility of entering production and scaling yields. As a project manager, I was focused on evaluating how our technology might shape particular markets, and developing marketing strategies for the products we were to develop.

When I arrived at Phoebus, the company had just initiated an effort on demonstrating enhanced solar cell performance with a metamaterial top layer. Simulation results, funded by a Phase I SBIR, had shown that deliberately designed metamaterials would be more effective in enhancing carrier generation in silicon – especially less expensive amorphous silicon – than heretofore developed solutions involving unstructured depositions of metallic nanoparticles. With this in mind, we set out to develop demonstration devices and characterize the scope of our opportunity.

This work was particularly interesting, since we had to develop fabrication protocols for a solar cell from scratch, and very quickly. While not technically novel, this technical challenge was a spectacular demonstration of how to quickly and effectively understand a field’s literature, extract from it the relevant unexpected morsels, and create functioning devices. The efficiency of the baseline cells we had made merely a month after getting started was similar to the work of more established groups!

In working so closely with an academic group, I had the opportunity to contribute to academic projects as well. One of the projects we completed was a demonstration of Babinet’s principle in subwavelength optical systems. The split-ring resonator (SRR) is a well-understood unit cell geometry for artificial magnetic metamaterials, used in both microwave and THz work. However, extending this mode of operation to the optical has proven difficult, since quantization and carrier confinement effects begin to play a larger role in structures of the requisite size. With that in mind, a complementary split ring resonator (cSRR) was proposed, with the logic that Babinet’s principle would provide bandpass where before there was a bandstop. We fabricated this device, and measured its performance.

Also, I we developed a suite of approaches to using diamond-phase carbon as a metamaterial dielectric. These results, under A. Golvin, are pending publication.

More important than these technical accomplishments were the meta-technical lessons extracted from this experience. Torn out of academic work, it was eye-opening to consider closely what the ecosystems looked like for the devices we were building, and to be motivated by a market (and not just a market of ideas).

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