Nanowires, Nanoneedles and Sub-Wavelength Structures: Enabling a New Era of Optoelectronic Technologies.
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There are intense interests in semiconductor structures with dimensions at the two ends of the nanometer regime. Materials with size on the order of a few nanometers, close to the de Broglie wavelength, are critical because their physical properties may be altered by its dimensions. On the other hand, materials with dimensions on the order of one hundred nanometer scale are of enormous interests because they open up a new window to re-examine the wave guiding properties in sub-wavelength structures. In this talk, I will discuss recent progress in these two areas.
We will discuss the synthesis and characteristics of III-V compound nanowires and nanoneedles that are monolithically grown on Si and sapphire inspite of a very large lattice mismatches (over 50% for the latter). The structures show excellent crystalline and optical quality. The nanowires are promising for ultra low threshold lasers and high efficiency solar cells. The nanoneedles, on the other hand, have an extremely sharp tip of a few atoms in diameter.
For the hundred-nm regime structures, we recently discovered a novel high index contrast subwavelength grating (HCG) structure, which showed an unprecedented effects on optical wave guiding and reflection properties. By varying the grating parameters, we show a single layer of uniform grating exhibits high-Q (14,000) resonator characteristics – again for surface-normal emission VCSELs.
Connie Chang-Hasnain is the John R. Whinnery Chair Professor of Electrical Engineering and Computer Sciences at the University of California, Berkeley, where she also serves as Director of the Center for Optoelectronic Nanostructured SemiconductoR Technologies (CONSRT) and Chair of Nanoscale Science and Engineering Graduate Group.
Prior to joining the Berkeley faculty, Dr. Chang-Hasnain was a member of the technical staff at Bellcore (1987–1992) and an Associate Professor of Electrical Engineering at Stanford University (1992–1996). Her research interests have been in vertical cavity surface emitting lasers and MEMS tunable optoelectronic devices and, most recently, nanostructured materials and nano-optoelectronic devices. Professor Chang-Hasnain was named a Presidential Faculty Fellow, Packard Fellow, and Sloan Research Fellow. She was awarded with an IEEE LEOS Distinguished Lecturer Award, IEEE LEOS William Streifer Award, National Academy of Engineering Gilbreth Lecturer Award, and OSA Nick Holonyak Jr. Award. She is a Fellow of the IEEE, OSA and IEE, and an Honorary Member of A.F. Ioffe Institute. Since January 2007, she is the Editor-in-Chief of the Journal of Lightwave Technology.