Thu, Nov 15, 2012 @ 02:00 PM - 03:00 PM
Ming Hsieh Department of Electrical Engineering
Conferences, Lectures, & Seminars
Speaker: Connie J. Chang-Hasnain, University of California, Berkeley
Talk Title: Flat Photonics Using High Contrast Metastructures
Abstract: A new class of planar optics has emerged using near-wavelength period gratings with a large refractive index contrast. This seemingly simple structure lends itself to extraordinary properties, which can be designed top-down based for integrated optics on a silicon substrate. In particular, the near-wavelength gratings with large index contrast wiht its surrounding materials are referred as high-contrast gratings (HCG). The extraordinary features include an ultra broadband (Δλ/λ>30%) high reflectivity (>99%) reflector for surface-normal incident light. Another feature is a high quality-factor resonance (Q>107) with surface-normal emission. We incorporated HCG as a replacement of conventional distributed Bragg reflectors (DBR) in vertical cavity surface emitting lasers (VCSELs) over a wide wavelength range from 850-nm to 1550-nm. We also demonstrated high-Q cavity with surface-normal input/output beam using a single HCG layer. This resonator is formed without a Fabry-Perot cavity!
By varying HCG dimensions, the reflection phase can be changed, which can be used to control the VCSEL wavelength. Most interestingly, a curved wave front can be obtained by locally changing each grating dimension. This leads to planar, single-layer lens and focusing reflectors with high focusing power, or arbitrary transmitted wavefront generator which can be used to split or route light.
The HCG can be designed to provide reflection and resonances for incident light at an oblique angle as well. A hollow-core waveguide can be made with two parallel HCGs with light guided in-between. The phase of reflection coefficient can be designed such that slow light can be obtained in a hollow-core waveguide. Finally, light propagation can be switched efficiently from surface-normal direction to an in-plane index-guided waveguide and vice versa.
In this talk, I will review the physical insights of the extraordinary properties and show that HCG can be easily designed using simple guidelines for chip-scale optics.
Biography: Connie Chang-Hasnain is the John R. Whinnery Chair Professor in the Electrical Engineering and Computer Sciences Department and Chair of the Nanoscale Science and Engineering (NSE) Graduate Group at the University of California, Berkeley. She received her Ph.D. from the same university in 1987. Prior to joining the Berkeley faculty, Dr. Chang-Hasnain was a member of the technical staff at Bellcore (1987–1992) and Associate Professor of Electrical Engineering at Stanford University (1992–1996). She is an Honorary Member of A.F. Ioffe Institute, a Chang Jiang Scholar Endowed Chair Professor at Tsinghua University, a Visiting Professor of Peking University and National Chiao Tung University.
Professor Chang-Hasnain’s research interests range from semiconductor optoelectronic devices to materials and physics, with current foci on nano-photonic materials and devices for chip-scale integrated optics. She has been honored with the IEEE David Sarnoff Award (2011), the OSA Nick Holonyak Jr. Award (2007), the IEEE LEOS William Streifer Award for Scientific Achievement (2003), and the Microoptics Award from Japan Society of Applied Physics (2009). Additionally, she has been awarded with a National Security Science and Engineering Faculty Fellowship by the Department of Defense (2008), a Humboldt Research Award (2009), and a Guggenheim Fellowship (2009). She was a member of the USAF Scientific Advisory Board, the IEEE LEOS Board of Governors, OSA Board of Directors, and the Board on Assessment of NIST Programs, National Research Council. She has been the Editor-in-Chief Journal of Lightwave Technology since 2007.
Location: Seeley G. Mudd Building (SGM) - 101
Audiences: Everyone Is Invited
Posted By: Marilyn Poplawski