Dr. Ganapathi S. Subramania Profile

Dr. Ganapathi S. Subramania

Technical Staff at Sandia National Labs

SPIE Involvement:

Conference Chair | Editorial Board Member: Journal of Nanophotonics | Editor | Author

Area of Expertise:

Photonic Crystals , Nanophotonics , Nanofabrication , Metamaterials , III-nitride photonics , Three dimensional photonic crystals

Proceedings Article | 13 March 2024 Presentation

Photonics with nanostructured III-nitride semiconductors

Ganapathi Subramania

Proceedings Volume PC12896, PC128960Q (2024) https://doi.org/10.1117/12.3012021

KEYWORDS: Photonic nanostructures, Laser nanostructuring, Semiconductors, Quantum photonics, Ultraviolet radiation, Quantum wells, Quantum light, Quantum control, Photonic crystals, Nanowires

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Proceedings Article | 3 August 2021 Presentation

Low refractive cladding in III-nitride photonics

Ganapathi Subramania, Nicholas Karl, Keshab Sapkota, George Wang, Igal Brener, Zachary Meinelt, Daniel Feezell

Proceedings Volume 11796, 117960C (2021) https://doi.org/10.1117/12.2596419

KEYWORDS: Cladding, Photonics, Gallium nitride, Refractive index, Photonic crystals, Nanowires, Laser optics, Etching, Electrochemical etching, Visible radiation

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Proceedings Article | 20 August 2020 Presentation

Opening Remarks by Conference Chairs

Stavroula Foteinopoulou, Ganapathi Subramania

Proceedings Volume 11461, 1146104 (2020) https://doi.org/10.1117/12.2580567

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Proceedings Article | 17 September 2018 Presentation

Voltage tuning of reflectance from a strongly coupled metasurface-semiconductor hybrid structure (Conference Presentation)

Raktim Sarma, Salvatore Campione, Michael Goldflam, Joshua Shank, Sean Smith, Jinhyun Noh, Peide Ye, Michael Sinclair, Ganapathi Subramania, Isaac Ruiz, Stephen Howell, Joel Wendt, Igal Brener

Proceedings Volume 10721, 107211E (2018) https://doi.org/10.1117/12.2321256

KEYWORDS: Reflectivity, Modulation, Beam steering, Dielectric polarization, Electronics, Semiconductors, Gold, Indium gallium arsenide, Doping, Scattering

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Proceedings Article | 26 July 2016 Presentation

Highly-efficient all-dielectric Huygens' surface holograms (Conference Presentation)

Katie Chong, Lei Wang, Isabelle Staude, Anthony James, Jason Dominguez, Ganapathi Subramania, Sheng Liu, Manuel Decker, Dragomir Neshev, Igal Brener, Yuri Kivshar

Proceedings Volume 9883, 988308 (2016) https://doi.org/10.1117/12.2227089

KEYWORDS: Holograms, Holography, Silicon, Optical design, Metamaterials, Resonators, Dielectrics

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Optical metasurfaces have developed as a breakthrough concept for advanced wave-front. Key to these “designer metasurfaces”[1] is that they provide full 360 degree phase coverage and that their local phase can be precisely controlled. The local control of phase, amplitude and polarization on an optically thin plane will lead to a new class of flat optical components in the areas of integrated optics, flat displays, energy harvesting and mid-infrared photonics, with increased performance and functionality. However, reflection and/or absorption losses as well as low polarization-conversion efficiencies pose a fundamental obstacle for achieving high transmission efficiencies that are required for practical applications. A promising way to overcome these limitations is the use of metamaterial Huygens’ surfaces [2-4], i.e., reflection-less surfaces that can also provide full 360 degree phase coverage in transmission. Plasmonic implementations of Huygens’ surfaces for microwave [2] and the mid-infrared spectral range [3], where the intrinsic losses of the metals are negligible, have been suggested, however, these designs cannot be transferred to near-infrared or even visible frequencies because of the high dissipative losses of plasmonic structures at optical frequencies. Here, we demonstrate the first holographic metasurface utilizing the concept of all-dielectric Huygens’ surfaces thereby achieving record transmission efficiencies of approximately 82% at 1477nm wavelength. Our low-loss Huygens’ surface is realized by two-dimensional subwavelength arrays of loss-less silicon nanodisks with both electric and magnetic dipole resonances [4]. By controlling the intrinsic properties of the resonances, i.e. their relative electric and magnetic polarizabilities, quality factors and spectral position, we can design silicon nanodisks to behave as near-ideal Huygens’ particles. This allows us to realize all-dielectric Huygens’ surfaces providing full 360 degree phase coverage that lack dissipative losses and also suppress unwanted reflections without relying on cross-polarization schemes that additionally suffer from polarization-conversion losses. We now use such Huygens’ surfaces in order to create a highly-efficient phase masks for the generation of optical holograms. By varying only one geometrical parameter, namely the lattice periodicity that can be controlled easily during the fabrication process we can effectively generate arbitrary hologram images from a 4-level phase discretization. In order to design the arrangement of the pixels in the metasurfaces, we calculate the phase mask required for a hologram generating the letters ‘hv’ in the hologram plane. In the next step the Huygens’ hologram is fabricated on a back-side polished SOI wafer by electron-beam lithography followed by a reactive-ion etching process. Then, we measure the phase of the generated hologram using a home-built Mach-Zehnder interferometer and perform a phase retrieval process to compare the experimental phase with the designed phase. Finally, we record the holographic image in the hologram plane and demonstrate that the device functionality is completely polarization insensitive with a transmission efficiency of 82%, in contrast to all the earlier works utilizing geometric phase. References [1] Yu et al., Nat. Mater. 13, 139 (2014). [2] Pfeiffer et al., Phys. Rev. Lett. 110, 197401 (2013). [3] Monticone et al., Phys. Rev. Lett. 110, 203903 (2013). [4] Decker et al., Adv. Opt. Mater. 3, 813 (2015).

Proceedings Article | 15 February 2012 Paper

Gallium-nitride-based logpile photonic crystals for visible lighting

G. Subramania, Q. Li, Y.-J. Lee, J. Figiel, C. Sanchez, G. Wang, A. Fischer, R. Biswas

Proceedings Volume 8249, 82490V (2012) https://doi.org/10.1117/12.915778

KEYWORDS: Gallium nitride, Photonic crystals, Refractive index, Light emitting diodes, Silica, Light sources and illumination, Solid state lighting, Electromagnetism, Visible radiation, Crystals

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Proceedings Article | 11 September 2006 Paper

Complete three dimensional gap photonic crystals in the near infrared and visible wavelengths for sensing applications

G. Subramania, Y. Lee, J. Verley, J. Fleming, I. El-Kady, T. Luk, P. Clem, I. Brener

Proceedings Volume 6322, 632204 (2006) https://doi.org/10.1117/12.682490

KEYWORDS: Photonic crystals, Silicon, Optical microcavities, Tungsten, Etching, Electron beams, Gold, Reflectivity, Sensors, Oxides

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Proceedings Article | 5 September 2006 Paper

New infrared photonic lattice coating

C. Schmidt, W. Sweatt, I. El-Kady, F. McCormick, D. Peters, S. Kravitz, J. Verley, U. Krishnamoorthy, D. Ingersoll, W. Yelton, G. Subramamia, J. Williams

Proceedings Volume 6289, 628912 (2006) https://doi.org/10.1117/12.679875

KEYWORDS: Gold, Reflectivity, Lithography, Refractive index, Thermography, Metals, Mirrors, Infrared coatings, Infrared photography, Infrared radiation

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