scispace - formally typeset
Search or ask a question
Author

Tsing-Hua Her

Bio: Tsing-Hua Her is an academic researcher from University of North Carolina at Charlotte. The author has contributed to research in topics: Laser & Femtosecond. The author has an hindex of 18, co-authored 89 publications receiving 2719 citations. Previous affiliations of Tsing-Hua Her include University of North Carolina at Chapel Hill & Harvard University.


Papers
More filters
Journal ArticleDOI
TL;DR: A novel method for three-dimensional optical data storage that has submicrometer size resolution, provides a large contrast in index of refraction, and is applicable to a wide range of transparent materials is presented.
Abstract: We present a novel method for three-dimensional optical data storage that has submicrometer size resolution, provides a large contrast in index of refraction, and is applicable to a wide range of transparent materials. Bits are recorded by use of a 0.65-N.A. objective to focus 100-fs laser pulses inside the material. The laser pulse produces a submicrometer-diameter structurally altered region with high contrast in index of refraction. We record binary information by writing such bits in multiple planes and read it out with a microscope objective with a short depth of field. We demonstrate data storage and retrieval with 2-microm in-plane bit spacing and 15-microm interplane spacing (17 Gbits/cm(3)). Scanning electron microscopy and atomic force microscopy show structural changes confined to an area 200 nm in diameter.

959 citations

Journal ArticleDOI
TL;DR: In this paper, the authors report that silicon surfaces develop an array of sharp conical spikes when irradiated with 500 laser pulses of 100-fs duration, 10kJ/m2 fluence in 500-Torr SF6 or Cl2.
Abstract: We report that silicon surfaces develop an array of sharp conical spikes when irradiated with 500 laser pulses of 100-fs duration, 10-kJ/m2 fluence in 500-Torr SF6 or Cl2. The spikes are up to 40-μm tall, and taper to about 1-μm diam at the tip. Irradiation of silicon surfaces in N2, Ne, or vacuum creates structured surfaces, but does not create sharp conical spikes.

785 citations

Journal ArticleDOI
TL;DR: In this article, it was shown that silicon surfaces develop arrays of sharp conical spikes when irradiated with 500-fs laser pulses in SF6 and the height of the spikes decreases with increasing pulse duration or decreasing laser fluence, and scales nonlinearly with the average separation between spikes.
Abstract: We find that silicon surfaces develop arrays of sharp conical spikes when irradiated with 500-fs laser pulses in SF6. The height of the spikes decreases with increasing pulse duration or decreasing laser fluence, and scales nonlinearly with the average separation between spikes. The spikes have the same crystallographic orientation as bulk silicon and always point along the incident direction of laser pulses. The base of the spikes has an asymmetric shape and its orientation is determined by the laser polarization. Our data suggest that both laser ablation and laser-induced chemical etching of silicon are involved in the formation of the spikes.

263 citations

Journal ArticleDOI
TL;DR: In this article, an all-optical 2R regenerator at 40 Gb/s that is based on self-phase modulation in fiber is presented, and the effect of fiber length, launch power into the fiber, and regenerator filter offset on the regenerator performance is investigated.
Abstract: Optimization of an all-optical 2R regenerator at 40 Gb/s that is based on self-phase modulation in fiber is presented. The effect of fiber length, launch power into the fiber, and regenerator filter offset on the regenerator performance are investigated. We show that all three parameters can be carefully chosen to maximize the pulse regeneration. When optimized, we demonstrate an improvement in Q value of 1.5 dB.

78 citations

Proceedings ArticleDOI
17 Mar 2002
TL;DR: In this article, a 40 Gbit/s pseudo-linear (non-soliton) transmission over 1000000 km of nonzero dispersion fiber is achieved using all-optical 2R regeneration and in-line synchronous modulation after every 400 km (4/spl times/100 km).
Abstract: Single-channel 40 Gbit/s pseudo-linear (non-soliton) transmission over 1000000 km of nonzero dispersion fiber is achieved using all-optical 2R regeneration and in-line synchronous modulation after every 400 km (4/spl times/100 km). Measured Q factors are better than 19 dB at several distances from 400 km to 1000000 km.

72 citations


Cited by
More filters
Journal ArticleDOI
TL;DR: In this article, the physical mechanisms and the main experimental parameters involved in femtosecond laser micromachining of transparent materials, and important emerging applications of the technology are described.
Abstract: Femtosecond laser micromachining can be used either to remove materials or to change a material's properties, and can be applied to both absorptive and transparent substances. Over the past decade, this technique has been used in a broad range of applications, from waveguide fabrication to cell ablation. This review describes the physical mechanisms and the main experimental parameters involved in the femtosecond laser micromachining of transparent materials, and important emerging applications of the technology. Interactions between laser and matter are fascinating and have found a wide range of applications. This article gives an overview of the fundamental physical mechanisms in the processing of transparent materials using ultrafast lasers, as well as important emerging applications of the technology.

2,533 citations

Journal ArticleDOI
TL;DR: In this paper, the main aspects of ultrashort laser pulse filamentation in various transparent media such as air (gases), transparent solids and liquids are introduced and discussed.

2,282 citations

Journal ArticleDOI
TL;DR: It is shown that plasmonic nanostructures of silver can concurrently use low-intensity visible light and thermal energy to drive catalytic oxidation reactions--such as ethylene epoxidation, CO oxidation, and NH₃ oxidation--at lower temperatures than their conventional counterparts that use only thermal stimulus.
Abstract: Catalysis plays a critical role in chemical conversion, energy production and pollution mitigation. High activation barriers associated with rate-limiting elementary steps require most commercial heterogeneous catalytic reactions to be run at relatively high temperatures, which compromises energy efficiency and the long-term stability of the catalyst. Here we show that plasmonic nanostructures of silver can concurrently use low-intensity visible light (on the order of solar intensity) and thermal energy to drive catalytic oxidation reactions--such as ethylene epoxidation, CO oxidation, and NH₃ oxidation--at lower temperatures than their conventional counterparts that use only thermal stimulus. Based on kinetic isotope experiments and density functional calculations, we postulate that excited plasmons on the silver surface act to populate O₂ antibonding orbitals and so form a transient negative-ion state, which thereby facilitates the rate-limiting O₂-dissociation reaction. The results could assist the design of catalytic processes that are more energy efficient and robust than current processes.

1,610 citations

Journal ArticleDOI
TL;DR: In this paper, the basic concepts and strategies adopted to minimize reflectance of anti-reflective coatings (ARCs) are described in greater detail and state-of-the-art fabrication techniques have been fully illustrated.
Abstract: Anti-reflective coatings (ARCs) have evolved into highly effective reflectance and glare reducing components for various optical and opto-electrical equipments. Extensive research in optical and biological reflectance minimization as well as the emergence of nanotechnology over the years has contributed to the enhancement of ARCs in a major way. In this study the prime objective is to give a comprehensive idea of the ARCs right from their inception, as they were originally conceptualized by the pioneers and lay down the basic concepts and strategies adopted to minimize reflectance. The different types of ARCs are also described in greater detail and the state-of-the-art fabrication techniques have been fully illustrated. The inspiration that ARCs derive from nature (‘biomimetics’) has been an area of major research and is discussed at length. The various materials that have been reportedly used in fabricating the ARCs have also been brought into sharp focus. An account of application of ARCs on solar cells and modules, contemporary research and associated challenges are presented in the end to facilitate a universal understanding of the ARCs and encourage future research.

1,047 citations

Journal ArticleDOI
TL;DR: In nanopore analytics, individual molecules pass through a single nanopore giving rise to detectable temporary blockades in ionic pore current, which ranges from nucleic acids, peptides, proteins, and biomolecular complexes to organic polymers and small molecules.
Abstract: In nanopore analytics, individual molecules pass through a single nanopore giving rise to detectable temporary blockades in ionic pore current. Reflecting its simplicity, nanopore analytics has gained popularity and can be conducted with natural protein as well as man-made polymeric and inorganic pores. The spectrum of detectable analytes ranges from nucleic acids, peptides, proteins, and biomolecular complexes to organic polymers and small molecules. Apart from being an analytical tool, nanopores have developed into a general platform technology to investigate the biophysics, physicochemistry, and chemistry of individual molecules (critical review, 310 references).

1,022 citations