2011 International Conference on Infrared, Millimeter, and Terahertz Waves, 2011
ABSTRACT Terahertz wave generation and detection using gaseous medium as both the THz wave emitte... more ABSTRACT Terahertz wave generation and detection using gaseous medium as both the THz wave emitter and sensor has drawn a great deal of attention. We report intense THz wave generation from two-color laser-induced air plasma at standoff distances of up to 30 m with peak THz electric field exceeding 1 kV/cm.
Frontiers in Optics 2008/Laser Science XXIV/Plasmonics and Metamaterials/Optical Fabrication and Testing, 2008
As a promising nonlinear optical medium, femtosecond-laser-induced plasma in gases has been studi... more As a promising nonlinear optical medium, femtosecond-laser-induced plasma in gases has been studied intensively over the past several years. It is not only used to generate and amplify terahertz (THz) waves, but also used to detect terahertz (THz) waves [1-3]. Recent studies show ...
2006 Conference on Lasers and Electro-Optics and 2006 Quantum Electronics and Laser Science Conference, 2006
We report the study of THz wave generation in air with the individually controlled fundamental ω ... more We report the study of THz wave generation in air with the individually controlled fundamental ω and its 2ω beams. Our results confirm that FWM in laser-induced plasma is the major mechanism of THz wave generation. In our experimental approach: a fundamental beam (ω) ...
2008 33rd International Conference on Infrared, Millimeter and Terahertz Waves, 2008
Using gases as the emitter and detector media in a THz system allows for good phase matching over... more Using gases as the emitter and detector media in a THz system allows for good phase matching over the full terahertz range (0.3 to 10 THz), without interruptions from crystal phonon modes or other instrument artifacts. A heterodyne technique facilitates coherent measurement of the electric field waveform, enabling this technique to be used for time-resolved spectroscopy in which a single measurement can continuously cover the entire terahertz region of the electromagnetic spectrum.
2006 Joint 31st International Conference on Infrared Millimeter Waves and 14th International Conference on Teraherz Electronics, 2006
ABSTRACT We report the use of air to sense broadband THz waves. Ambient air, with about 79% nitro... more ABSTRACT We report the use of air to sense broadband THz waves. Ambient air, with about 79% nitrogen and 21% oxygen, exhibits remarkable performance for the generation and detection of pulsed THz waves with femtosecond laser beams.
2006 Joint 31st International Conference on Infrared Millimeter Waves and 14th International Conference on Teraherz Electronics, 2006
ABSTRACT We demonstrate generation, manipulation, amplification, and detection of highly directio... more ABSTRACT We demonstrate generation, manipulation, amplification, and detection of highly directional broadband THz waves in laser-induced air plasma.
2009 34th International Conference on Infrared, Millimeter, and Terahertz Waves, 2009
ABSTRACT A device for phase and polarization control of omega (800 nm) and its second harmonic 2 ... more ABSTRACT A device for phase and polarization control of omega (800 nm) and its second harmonic 2 omega (400 nm) beams is presented for intense THz generation from laser-induced gas plasma in gas cells. Long-term stability is achieved using an in-line design with a quartz wedge pair and alpha-BBO birefringent plates for phase control and a dual wavelength waveplate to align the polarization of omega and 2 omega. This phase compensator, in an in-line configuration, is expected to be used to generate intense THz waves at standoff distances with high dynamic range.
Nonlinear Optics: Materials, Fundamentals and Applications, 2007
ABSTRACT We report the generation, manipulation, amplification and detection of THz waves in lase... more ABSTRACT We report the generation, manipulation, amplification and detection of THz waves in laser induced air plasma. Four-wave mixing is the main mechanism of THz wave photonics in plasma.
2007 Conference on Lasers and Electro-Optics (CLEO), 2007
We report the first demonstration of both incoherent and coherent detection of pulsed terahertz w... more We report the first demonstration of both incoherent and coherent detection of pulsed terahertz waves using ambient air or laser-induced air plasma as the sensor through a third-order nonlinear optical process with femtosecond laser pulses.
Nonlinear Frequency Generation and Conversion: Materials, Devices, and Applications X, 2011
THz time domain spectroscopy has been largely applied on the measurement of semiconductor, electr... more THz time domain spectroscopy has been largely applied on the measurement of semiconductor, electro-optic crystals, and selected chemical, biological and explosive materials. The objective of this paper is to report THz gas photonics and its applications, ...
ABSTRACT A black silicon structure with high-aspect-ratio surface spikes was designed and fabrica... more ABSTRACT A black silicon structure with high-aspect-ratio surface spikes was designed and fabricated in vacuum, resulting in absorptance >90% over the range of 200-2500 nm. It is demonstrated that annealing, an essential step in the fabrication of semiconductor devices, has almost no effect on the infrared absorption of this material, while the infrared absorption of an identical structure fabricated in a SF6 drops dramatically after the annealing process. The characteristic of high infrared absorption and annealing-insensitivity is attributed to both the high-aspect-ratio structure and the phosphor-doped low impedance silicon. These results are important for the fabrication of highly efficient optoelectronic devices. (C) 2014 AIP Publishing LLC.
2009 IEEE Conference on Technologies for Homeland Security, 2009
Terahertz wave generation and detection using air as both the terahertz wave emitter and sensor m... more Terahertz wave generation and detection using air as both the terahertz wave emitter and sensor media through nonlinear optical processes similar to four-wave mixing (named terahertz air photonics) were introduced. Due to the unique features of this technique, it is possible to find applications for terahertz air photonics in remote sensing and identification of explosives by sending optical beams rather than terahertz beams far away and generating and detecting terahertz waves in the vicinity of the target. As one of the most important steps for the standoff explosive detection application, we demonstrated standoff intense terahertz wave generation by sending an 800-nm femtosecond laser pulse and its second harmonic at a distance of 17 meters, which is the current limit allowed by the laser pulse energy and the length of our laboratory. A phase compensator was specifically designed to compensate for the temporal walk-off between the 800-nm pulse and its second harmonic travelling in dispersive air.
The Fourier transform-limited electromagnetic pulse has been regarded to be free of chirps for a ... more The Fourier transform-limited electromagnetic pulse has been regarded to be free of chirps for a long time. This is no longer true if the pulse duration goes down to or less than one optical cycle. We report the experimental observation of intrinsic chirps in such pulses with the ...
The Journal of microwave power and electromagnetic energy : a publication of the International Microwave Power Institute, 2010
This study provides a facile method to map the microwave field distribution in a multimode microw... more This study provides a facile method to map the microwave field distribution in a multimode microwave cavity. Anhydrous calcium sulfate powder was used to make the gypsum plates that were used as the carrying medium. Cobalt chloride hexahydrate, whose color changes when losing part or all of its crystal waters, was selected as an indicator of the energy absorption. The cobalt chloride aqueous solution at a concentration of 1.6% was absorbed by the dried gypsum plates. After introducing the plates into a microwave field, those areas that receive more microwave energy were preferably heated, resulting in the release of the moisture and consequently the loss of crystal water from the cobalt chloride hexahydrate. The color change on the plate formed a color map indicating the microwave field distribution. This method was used to investigate the energy distribution of a microwave oven by placing single or multiple plates in horizontal or vertical positions at different locations in the ca...
International Journal of High Speed Electronics and Systems, 2007
262 X, Xie et al. than 100 kV/cm has been reported by using a similar experimental arrangement wi... more 262 X, Xie et al. than 100 kV/cm has been reported by using a similar experimental arrangement with shorter laser pulses and focusing lens with short focal length 8. Power dependence measurements have been performed to verify the proposed mechanism while different groups obtained ...
In situ magnetic annealing effects on c-axis-preferred multiferroic BiFeO 3 /CoFe 2 O 4 bilayered... more In situ magnetic annealing effects on c-axis-preferred multiferroic BiFeO 3 /CoFe 2 O 4 bilayered by chemical solution deposition route are investigated. It is observed that magnetic annealing can enhance the crystallization quality, texture and densification as well as dielectric properties. In addition, the magnetolosses decrease with increasing the magnetic fields. Moreover, both increase of the polarization and decrease of the leakage current due to magnetic annealing are beneficial for potential applications of BiFeO 3 films.
In this work carbonyl iron/La 0.6 Sr 0.4 MnO 3 composites were prepared to develop super-thin mic... more In this work carbonyl iron/La 0.6 Sr 0.4 MnO 3 composites were prepared to develop super-thin microwave absorbing materials. The complex permittivity, permeability and microwave absorption properties are investigated in the frequency range of 8-12 GHz. An optimal reflection loss of À 12.4 dB is reached at 10.5 GHz with a matching thickness of 0.8 mm. The thickness of carbonyl iron/La 0.6 Sr 0.4 MnO 3 absorber is thinner, compared with conventional carbonyl iron powders with the same absorption properties. The bandwidth with a reflection loss exceeding À 7.4 dB is obtained in the whole measured frequency range with the thickness of 0.8 mm. The excellent microwave absorption properties are attributed to a better electromagnetic matching established by the combination of the enhanced dielectric loss and nearly invariable magnetic loss with the addition of La 0.6 Sr 0.4 MnO 3 nanoparticles in the composites. Our work indicates that carbonyl iron/La 0.6 Sr 0.4 MnO 3 composites may have an important application in wideband and super-thin electromagnetic absorbers in the frequency range of 8 À 12 GHz.
Monodisperse porous Ni0.5Zn0.5Fe2O4 nanospheres have been successfully synthesized by the solvoth... more Monodisperse porous Ni0.5Zn0.5Fe2O4 nanospheres have been successfully synthesized by the solvothermal method. The diameter of the nanospheres can be tuned by controlling the reactant concentration. Lower reactant concentration is favoured for the synthesis of mesoporous Ni0.5Zn0.5Fe2O4 nanospheres with higher surface area. The electrochemical results show that mesoporous Ni0.5Zn0.5Fe2O4 nanospheres exhibit high reversible specific capacity (1110 mAh g−1) for Li storage and high capacity retention, with 700 mAh g−1 retained up to 50 cycles. The excellent electrochemical properties could be attributed to the large surface area and mesoporous structure. The results suggest that Ni0.5Zn0.5Fe2O4 could be a promising high capacity anode material for lithium ion batteries.
2011 International Conference on Infrared, Millimeter, and Terahertz Waves, 2011
ABSTRACT Terahertz wave generation and detection using gaseous medium as both the THz wave emitte... more ABSTRACT Terahertz wave generation and detection using gaseous medium as both the THz wave emitter and sensor has drawn a great deal of attention. We report intense THz wave generation from two-color laser-induced air plasma at standoff distances of up to 30 m with peak THz electric field exceeding 1 kV/cm.
Frontiers in Optics 2008/Laser Science XXIV/Plasmonics and Metamaterials/Optical Fabrication and Testing, 2008
As a promising nonlinear optical medium, femtosecond-laser-induced plasma in gases has been studi... more As a promising nonlinear optical medium, femtosecond-laser-induced plasma in gases has been studied intensively over the past several years. It is not only used to generate and amplify terahertz (THz) waves, but also used to detect terahertz (THz) waves [1-3]. Recent studies show ...
2006 Conference on Lasers and Electro-Optics and 2006 Quantum Electronics and Laser Science Conference, 2006
We report the study of THz wave generation in air with the individually controlled fundamental ω ... more We report the study of THz wave generation in air with the individually controlled fundamental ω and its 2ω beams. Our results confirm that FWM in laser-induced plasma is the major mechanism of THz wave generation. In our experimental approach: a fundamental beam (ω) ...
2008 33rd International Conference on Infrared, Millimeter and Terahertz Waves, 2008
Using gases as the emitter and detector media in a THz system allows for good phase matching over... more Using gases as the emitter and detector media in a THz system allows for good phase matching over the full terahertz range (0.3 to 10 THz), without interruptions from crystal phonon modes or other instrument artifacts. A heterodyne technique facilitates coherent measurement of the electric field waveform, enabling this technique to be used for time-resolved spectroscopy in which a single measurement can continuously cover the entire terahertz region of the electromagnetic spectrum.
2006 Joint 31st International Conference on Infrared Millimeter Waves and 14th International Conference on Teraherz Electronics, 2006
ABSTRACT We report the use of air to sense broadband THz waves. Ambient air, with about 79% nitro... more ABSTRACT We report the use of air to sense broadband THz waves. Ambient air, with about 79% nitrogen and 21% oxygen, exhibits remarkable performance for the generation and detection of pulsed THz waves with femtosecond laser beams.
2006 Joint 31st International Conference on Infrared Millimeter Waves and 14th International Conference on Teraherz Electronics, 2006
ABSTRACT We demonstrate generation, manipulation, amplification, and detection of highly directio... more ABSTRACT We demonstrate generation, manipulation, amplification, and detection of highly directional broadband THz waves in laser-induced air plasma.
2009 34th International Conference on Infrared, Millimeter, and Terahertz Waves, 2009
ABSTRACT A device for phase and polarization control of omega (800 nm) and its second harmonic 2 ... more ABSTRACT A device for phase and polarization control of omega (800 nm) and its second harmonic 2 omega (400 nm) beams is presented for intense THz generation from laser-induced gas plasma in gas cells. Long-term stability is achieved using an in-line design with a quartz wedge pair and alpha-BBO birefringent plates for phase control and a dual wavelength waveplate to align the polarization of omega and 2 omega. This phase compensator, in an in-line configuration, is expected to be used to generate intense THz waves at standoff distances with high dynamic range.
Nonlinear Optics: Materials, Fundamentals and Applications, 2007
ABSTRACT We report the generation, manipulation, amplification and detection of THz waves in lase... more ABSTRACT We report the generation, manipulation, amplification and detection of THz waves in laser induced air plasma. Four-wave mixing is the main mechanism of THz wave photonics in plasma.
2007 Conference on Lasers and Electro-Optics (CLEO), 2007
We report the first demonstration of both incoherent and coherent detection of pulsed terahertz w... more We report the first demonstration of both incoherent and coherent detection of pulsed terahertz waves using ambient air or laser-induced air plasma as the sensor through a third-order nonlinear optical process with femtosecond laser pulses.
Nonlinear Frequency Generation and Conversion: Materials, Devices, and Applications X, 2011
THz time domain spectroscopy has been largely applied on the measurement of semiconductor, electr... more THz time domain spectroscopy has been largely applied on the measurement of semiconductor, electro-optic crystals, and selected chemical, biological and explosive materials. The objective of this paper is to report THz gas photonics and its applications, ...
ABSTRACT A black silicon structure with high-aspect-ratio surface spikes was designed and fabrica... more ABSTRACT A black silicon structure with high-aspect-ratio surface spikes was designed and fabricated in vacuum, resulting in absorptance >90% over the range of 200-2500 nm. It is demonstrated that annealing, an essential step in the fabrication of semiconductor devices, has almost no effect on the infrared absorption of this material, while the infrared absorption of an identical structure fabricated in a SF6 drops dramatically after the annealing process. The characteristic of high infrared absorption and annealing-insensitivity is attributed to both the high-aspect-ratio structure and the phosphor-doped low impedance silicon. These results are important for the fabrication of highly efficient optoelectronic devices. (C) 2014 AIP Publishing LLC.
2009 IEEE Conference on Technologies for Homeland Security, 2009
Terahertz wave generation and detection using air as both the terahertz wave emitter and sensor m... more Terahertz wave generation and detection using air as both the terahertz wave emitter and sensor media through nonlinear optical processes similar to four-wave mixing (named terahertz air photonics) were introduced. Due to the unique features of this technique, it is possible to find applications for terahertz air photonics in remote sensing and identification of explosives by sending optical beams rather than terahertz beams far away and generating and detecting terahertz waves in the vicinity of the target. As one of the most important steps for the standoff explosive detection application, we demonstrated standoff intense terahertz wave generation by sending an 800-nm femtosecond laser pulse and its second harmonic at a distance of 17 meters, which is the current limit allowed by the laser pulse energy and the length of our laboratory. A phase compensator was specifically designed to compensate for the temporal walk-off between the 800-nm pulse and its second harmonic travelling in dispersive air.
The Fourier transform-limited electromagnetic pulse has been regarded to be free of chirps for a ... more The Fourier transform-limited electromagnetic pulse has been regarded to be free of chirps for a long time. This is no longer true if the pulse duration goes down to or less than one optical cycle. We report the experimental observation of intrinsic chirps in such pulses with the ...
The Journal of microwave power and electromagnetic energy : a publication of the International Microwave Power Institute, 2010
This study provides a facile method to map the microwave field distribution in a multimode microw... more This study provides a facile method to map the microwave field distribution in a multimode microwave cavity. Anhydrous calcium sulfate powder was used to make the gypsum plates that were used as the carrying medium. Cobalt chloride hexahydrate, whose color changes when losing part or all of its crystal waters, was selected as an indicator of the energy absorption. The cobalt chloride aqueous solution at a concentration of 1.6% was absorbed by the dried gypsum plates. After introducing the plates into a microwave field, those areas that receive more microwave energy were preferably heated, resulting in the release of the moisture and consequently the loss of crystal water from the cobalt chloride hexahydrate. The color change on the plate formed a color map indicating the microwave field distribution. This method was used to investigate the energy distribution of a microwave oven by placing single or multiple plates in horizontal or vertical positions at different locations in the ca...
International Journal of High Speed Electronics and Systems, 2007
262 X, Xie et al. than 100 kV/cm has been reported by using a similar experimental arrangement wi... more 262 X, Xie et al. than 100 kV/cm has been reported by using a similar experimental arrangement with shorter laser pulses and focusing lens with short focal length 8. Power dependence measurements have been performed to verify the proposed mechanism while different groups obtained ...
In situ magnetic annealing effects on c-axis-preferred multiferroic BiFeO 3 /CoFe 2 O 4 bilayered... more In situ magnetic annealing effects on c-axis-preferred multiferroic BiFeO 3 /CoFe 2 O 4 bilayered by chemical solution deposition route are investigated. It is observed that magnetic annealing can enhance the crystallization quality, texture and densification as well as dielectric properties. In addition, the magnetolosses decrease with increasing the magnetic fields. Moreover, both increase of the polarization and decrease of the leakage current due to magnetic annealing are beneficial for potential applications of BiFeO 3 films.
In this work carbonyl iron/La 0.6 Sr 0.4 MnO 3 composites were prepared to develop super-thin mic... more In this work carbonyl iron/La 0.6 Sr 0.4 MnO 3 composites were prepared to develop super-thin microwave absorbing materials. The complex permittivity, permeability and microwave absorption properties are investigated in the frequency range of 8-12 GHz. An optimal reflection loss of À 12.4 dB is reached at 10.5 GHz with a matching thickness of 0.8 mm. The thickness of carbonyl iron/La 0.6 Sr 0.4 MnO 3 absorber is thinner, compared with conventional carbonyl iron powders with the same absorption properties. The bandwidth with a reflection loss exceeding À 7.4 dB is obtained in the whole measured frequency range with the thickness of 0.8 mm. The excellent microwave absorption properties are attributed to a better electromagnetic matching established by the combination of the enhanced dielectric loss and nearly invariable magnetic loss with the addition of La 0.6 Sr 0.4 MnO 3 nanoparticles in the composites. Our work indicates that carbonyl iron/La 0.6 Sr 0.4 MnO 3 composites may have an important application in wideband and super-thin electromagnetic absorbers in the frequency range of 8 À 12 GHz.
Monodisperse porous Ni0.5Zn0.5Fe2O4 nanospheres have been successfully synthesized by the solvoth... more Monodisperse porous Ni0.5Zn0.5Fe2O4 nanospheres have been successfully synthesized by the solvothermal method. The diameter of the nanospheres can be tuned by controlling the reactant concentration. Lower reactant concentration is favoured for the synthesis of mesoporous Ni0.5Zn0.5Fe2O4 nanospheres with higher surface area. The electrochemical results show that mesoporous Ni0.5Zn0.5Fe2O4 nanospheres exhibit high reversible specific capacity (1110 mAh g−1) for Li storage and high capacity retention, with 700 mAh g−1 retained up to 50 cycles. The excellent electrochemical properties could be attributed to the large surface area and mesoporous structure. The results suggest that Ni0.5Zn0.5Fe2O4 could be a promising high capacity anode material for lithium ion batteries.
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