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Ultrashort Lasers to Increase Efficiency in Solar Energy Harvesting via Intermediate States, at 2014 High Power Laser Ablation and Beamed Energy Propulsion Conference (Santa Fe, NM), Wednesday, April 23, 2014:
talk_2309.pdf
Shining intense, ultrashort laser pulses on the surface of a crystalline silicon wafer drastically changes the optical, material and electronic properties of the wafer. The process has two effects: it structures the surface and incorporate dopants into the sample to a concentration highly exceeding the equilibrium solubility limit. This femtosecond laser "hyperdoping technique" enables the fabrication of defect- and bandgap engineered semiconductors, and laser texturing further enhances the optical density through excellent light trapping. Hyperdoped silicon opens the door for novel... Read more about Ultrashort Lasers to Increase Efficiency in Solar Energy Harvesting via Intermediate States
Black silicon, at 2014 International High Power Laser Ablation Conference (Santa Fe, NM), Monday, April 21, 2014:
talk_2141.pdf
Shining intense, ultrashort laser pulses on the surface of a crystalline silicon wafer drastically changes the optical, material and electronic properties of the wafer. The resulting textured surface is highly absorbing and looks black to the eye. The properties of this 'black silicon' make it useful for a wide range of commercial devices. In particular, we have been able to fabricate highly-sensitive PIN photodetectors using this material. The sensitivity extends to wavelengths of 1600 nm making them particularly useful for applications in communications and remote sensing.
Black silicon and the quest for intermediate band semiconductors, at Laser-Based Micro and Nano Processing VIII, Photonics West 2014 (San Francisco, CA), Thursday, February 6, 2014:
talk_2198.pdf
Shining intense, ultrashort laser pulses on the surface of a crystalline silicon wafer drastically changes the optical, material and electronic properties of the wafer. The process has two effects: it structures the surface and incorporate dopants into the sample to a concentration highly exceeding the equilibrium solubility limit. This femtosecond laser "hyperdoping technique" enables the fabrication of defect- and bandgap engineered semiconductors, and laser texturing further enhances the optical density through excellent light trapping. Hyperdoped silicon opens the door for novel... Read more about Black silicon and the quest for intermediate band semiconductors
Subcellular surgery and nanosurgery, at Photonics West 2014 (CA), Thursday, February 6, 2014:
talk_2267.pdf
Gene therapy is the use of DNA as an agent to cure or slow down the progression of a disease. A crucial requirement for gene therapy is the efficient and safe introduction of genetic vectors into mammalian cells. We developed a high-efficiency, low-toxicity, spatially-selective and high-throughput transfection method using fs laser induced-plasmons on a nanostructured substrate. We specifically compare two designs of plasmonic substrates (whole pyramid arrays and tipless pyramid arrays) using FDTD simulations and microbubble experiments. We then explore the laser parameter space to optimize... Read more about Subcellular surgery and nanosurgery
Dirac-cone based negative/zero/positive refractive index metamaterials, at SPIE Photonics West: Photonic and Phononic Properties of Engineered Nanostructures IV (San Francisco, California), Thursday, February 6, 2014
Based on accidental degeneracy, a Dirac-cone can be formed at the center of the Brillouin zone of a photonic crystal, which can be treated as a homogeneous bulk metamaterial in the vicinity of Dirac-point. In the vicinity below (above) the Dirac-point, the backward-wave (forward-wave) implies negative (positive) n_eff; at Dirac-point, k=0 induces zero n_eff. This negative/zero/positive refractive index shows low-loss and good impedance matching to free-space. According to this principle, we designed a Dirac-cone based metamaterial consisting of 2D square array of silicon pillars operating... Read more about Dirac-cone based negative/zero/positive refractive index metamaterials
Black silicon and the quest for intermediate band semiconductors, at Laser-Based Micro and Nano Processing VIII, Photonics West 2014 (San Francisco, CA), Thursday, February 6, 2014:
talk_2198.pdf
Shining intense, ultrashort laser pulses on the surface of a crystalline silicon wafer drastically changes the optical, material and electronic properties of the wafer. The process has two effects: it structures the surface and incorporate dopants into the sample to a concentration highly exceeding the equilibrium solubility limit. This femtosecond laser "hyperdoping technique" enables the fabrication of defect- and bandgap engineered semiconductors, and laser texturing further enhances the optical density through excellent light trapping. Hyperdoped silicon opens the door for novel... Read more about Black silicon and the quest for intermediate band semiconductors
2D impedance-matched zero-index metamaterial, at SPIE Photonics West: Photonic and Phononic Properties of Engineered Nanostructures IV (San Francisco, California), Wednesday, February 5, 2014
Recent efforts to achieve metamaterials with a vanishing refractive index take advantage of the low index at a photonic band edge. This behavior is accompanied by a divergent impedance, resulting in inefficient transmission. We investigate the nature of this discontinuity and show that it can be removed by tuning the electric and magnetic response of the metamaterial. We present a design for a 2D zero-index metamaterial based on this concept. The metamaterial is entirely dielectric, which results in low-loss transmission at the design wavelength of 1.55um. This behavior is confirmed using... Read more about 2D impedance-matched zero-index metamaterial
Nonlinear refraction in rutile TiO2, at SPIE Photonics West: Nonlinear Frequency Generation and Conversion: Materials, Devices, and Applications XIII (San Francisco, California), Tuesday, February 4, 2014
Titanium dioxide (TiO2) has attractive optical properties for nonlinear optical applications ranging from telecommunication to interconnect wavelengths (800–1600 nm). TiO2 demonstrates large linear and nonlinear refractive indices, wide transparency from the infrared to as low as 400 nm wavelengths, and low two-photon absorption for wavelengths longer than 800 nm. We use the Z-scan technique to investigate the nonlinear refraction and multiphoton absorption of bulk rutile TiO2 for wavelengths ranging from 800–1600 nm. Using our results, we calculate nonlinear figures of merit and discuss... Read more about Nonlinear refraction in rutile TiO2
Laser-processing of semiconductors and (some) applications , at HUCE Lunch Seminar, Harvard University (Cambridge, MA), Friday, January 31, 2014:
talk_2261.pdf
Shining intense, ultrashort laser pulses on the surface of a crystalline silicon wafer drastically changes the optical, material and electronic properties of the wafer. The resulting textured surface is highly absorbing and looks black to the eye. The properties of this 'black silicon' make it useful for a wide range of commercial devices. In particular, we have been able to fabricate highly-sensitive PIN photodetectors using this material. The sensitivity extends to wavelengths of 1600 nm making them particularly useful for applications in communications and remote sensing.

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