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Christopher Evans

Submicrometer-width TiO2 waveguides, at CLEO (San Jose, CA), Monday, May 7, 2012:
talk_1961.pdf
We fabricate submicrometer-width TiO2 strip waveguides and measure optical losses at 633, 780, and 1550 nm. Losses of 30, 13, and 4 dB/cm (respectively) demonstrate that TiO2 is suitable for visible-to-infrared on-chip microphotonic devices.
Reinventing the light switch: logic with photons, at Physics Colloquium, University of Massachusetts, Lowell (Lowell, MA), Wednesday, April 25, 2012:
talk_1927.pdf
Future computers and communications systems will require extremely fast logic operations that cannot be achieve efficiently using electronics. By using nonlinear optical materials with nano-scale structuring, we will show how to replace these “slow” electrons with photons to achieve logic operations on an ultrafast time scale.
Simultaneous multiphoton absorption in rutile (TiO2) across the half-bandgap, at Photonics West 2012 (San Francisco, CA), Thursday, January 26, 2012:
talk_1876.pdf
Future optical systems require compact, ultra-fast devices capable of switching and logic across a wide range of wavelengths. To realize this goal, ultrafast nonlinearities must be exploited while maintaining manageable linear losses and nonlinear absorption. We present TiO2 as a nonlinear material to meet these needs. TiO2 is highly transparent for wavelengths > 400 nm and possesses both high linear and nonlinear refractive indices. We measurements the nonlinear index and multiphoton absorption in bulk TiO2 (rutile) using the z-scan technique near the half bandgap (800 nm). Using... Read more about Simultaneous multiphoton absorption in rutile (TiO2) across the half-bandgap
TiO2 nanophotonic waveguides for on-chip nonlinear optical devices, at Photonics West 2012 (San Francisco, CA), Monday, January 23, 2012:
talk_1875.pdf
Titanium dioxide (TiO2) is a promising material for nonlinear photonic applications. Its large bandgap (> 3 eV) means it is highly transparent and has minimal two photon absorption over a wide wavelength range. TiO2’s high linear and nonlinear refractive indices (> 2 and 25 × that of silica at 800 nm, respectively) allow for high optical confinement in nanophotonic structures, such as waveguides, photonic crystals and resonators, and efficient nonlinear interactions. Thus, TiO2 is a potential platform for on-chip nonlinear optical devices operating across the three traditional... Read more about TiO2 nanophotonic waveguides for on-chip nonlinear optical devices
Nonlinear optics at the nanoscale, at 22nd General Congress of the International Commission for Optics (ICO-22) (Puebla, Mexico), Monday, August 15, 2011:
talk_1696.pdf
We explore nonlinear optical phenomena at the nanoscale by launching femtosecond laser pulses into long silica nanowires. Using evanescent coupling between wires we demonstrate a number of nanophotonic devices. At high intensity the nanowires produce a strong supercontinuum over short interaction lengths (less than 20 mm) and at a very low energy threshold (about 1 nJ), making them ideal sources of coherent white-light for nanophotonic applications. The spectral broadening reveals an optimal fiber diameter to enhance nonlinear effects with minimal dispersion. We also present a device that... Read more about Nonlinear optics at the nanoscale
Thermally managed Z-scan measurements of titanium dioxide thin films, at Photonics West (San Francisco, CA), Thursday, January 27, 2011:
talk_1697.pdf
We will present measurements of the complex nonlinear response of sputtered amorphous and polycrystalline titanium dioxide (TiO2) thin films using the thermally managed z-scan technique. Using a Ti:Sapphire laser with 100-fs pulses at 800 nm, we observe ultrafast electronic effects near TiO2's half band-gap. We explore the relation between material processing parameters and observed nonlinearity. In addition, we will discuss the consequences for applications such as all-optical switching.
TiO2 as a material platform for all-optical logic, at Horizons of Nanophotonics and Nanoelectronics, Harvard University (Cambridge, MA), Monday, December 20, 2010:
talk_1703.pdf
As the volume of internet traffic worldwide explodes and processing demands continually increase, solutions are required to overcome the inherent speed limitations of electronic devices. In particular, there is a need for all-optical devices, with their higher bandwidth and transmission rate, to replace various electronic functions such as routing data between processors and logic operations. We identified TiO2 as a promising yet unexplored material platform for ultrafast, on-chip nonlinear optical devices. TiO2 has a high nonlinear index of refraction (n2), enabling such operations as all-... Read more about TiO2 as a material platform for all-optical logic

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