scholarly journals Giant enhancement of THz-frequency optical nonlinearity by phonon polariton in ionic crystals

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Yao Lu ◽  
Qi Zhang ◽  
Qiang Wu ◽  
Zhigang Chen ◽  
Xueming Liu ◽  
...  
Keyword(s):  
Near Infrared ◽  
Optical Nonlinearity ◽  
Ionic Crystals ◽  
Nonlinear Optical Susceptibility ◽  
Time Resolved ◽  
Light Coupling ◽  
Tremendous Progress ◽  
Fundamental Research ◽  
Ionic Contribution ◽  
Time Resolved Imaging

AbstractThe field of nonlinear optics has grown substantially in past decades, leading to tremendous progress in fundamental research and revolutionized applications. Traditionally, the optical nonlinearity for a light wave at frequencies beyond near-infrared is observed with very high peak intensity, as in most materials only the electronic nonlinearity dominates while ionic contribution is negligible. However, it was shown that the ionic contribution to nonlinearity can be much larger than the electronic one in microwave experiments. In the terahertz (THz) regime, phonon polariton may assist to substantially trigger the ionic nonlinearity of the crystals, so as to enhance even more the nonlinear optical susceptibility. Here, we experimentally demonstrate a giant second-order optical nonlinearity at THz frequency, orders of magnitude higher than that in the visible and microwave regimes. Different from previous work, the phonon-light coupling is achieved under a phase-matching setting, and the dynamic process of nonlinear THz generation is directly observed in a thin-film waveguide using a time-resolved imaging technique. Furthermore, a nonlinear modification to the Huang equations is proposed to explain the observed nonlinearity enhancement. This work brings about an effective approach to achieve high nonlinearity in ionic crystals, promising for applications in THz nonlinear technologies.

Applications and Techniques for 2D Picosecond Imaging for Circuit Analysis

2014 ◽  
Author(s):  
Franco Stellari ◽  
Peilin Song ◽  
Alan J. Weger
Keyword(s):  
Spectral Analysis ◽  
Reverse Engineering ◽  
Near Infrared ◽  
Circuit Analysis ◽  
Time Resolved ◽  
Imaging Capability ◽  
Specific Focus ◽  
Time Resolved Imaging ◽  
Vlsi Chips

Abstract In this paper, we present the latest results obtained with a 2D Picosecond Imaging Circuit Analysis (PICA) camera with enhanced Near InfraRed (NIR) sensitivity [1] for taking 2D Time Resolved Emission (TRE). We will discuss key applications where the time-resolved imaging capability is very effective in reducing the debug time and improving the interpretation of the failure signatures of several VLSI chips. Besides conventional chip diagnostics, specific focus will be dedicated to new areas of applications, such as security and reverse engineering [2]. We will also discuss spectral analysis and other techniques that can be used to extract valuable information from the PICA dataset.

Efficient Near Infrared Si/Ge Quantum Dot Photo-Detector Based on a Heterojunction Bipolar Transistor

2003 ◽  
Vol 770 ◽  
Author(s):  
Anders Elfving ◽  
Mats Larsson ◽  
Per-Olof Holtz ◽  
Göran V. Hansson ◽  
Wei-Xin Ni
Keyword(s):  
Near Infrared ◽  
Layer Structure ◽  
Electrical Contact ◽  
Fold Increase ◽  
Normal Incidence ◽  
Bipolar Transistor ◽  
Heterojunction Bipolar Transistor ◽  
Time Resolved ◽  
Light Coupling ◽  
Ge Quantum Dot

AbstractGe dots embedded in Si offer the possibility of Si-based light detection at 1.3-1.55 μm. In this communication, we report a very efficient photo-detector based on a Si/SiGe heterojunction bipolar transistor structure with 10 Ge dot layers (8 ML Ge each) incorporated in the basecollector junction. The device structures were grown using low-temperature molecular beam epitaxy, and fabricated for both normal and edge incidence with no electrical contact to the base. The processed Ge-dot transistor detectors revealed a rather low dark current density, 0.01 mA/cm2 at -2 V. Photoconductivity measurements were performed at room temperature. At 1.31 μm, responsivity values of 50 mA/W at normal incidence have been directly measured at Vce = -4 V, without involving any rescaling factor due to light coupling. This value is a ∼250-fold increase compared to a reference p-i-n diode with the same dot layer structure, due to the current amplification function of the transistor. For a rib waveguide device, a very high responsivity value of about 470 mA/W (Vce = -4V) has been obtained at 1.31 μm. Measurements were also performed at 1.55 μm, and the photo-response of the waveguide phototransistor was 25 mA/W, which is again a large improvement compared with the reference waveguide photodiode (∼1 mA/W). Moreover, time-resolved photoconductivity measurements have been carried out. The results have indicated that the device frequency performance is primarily limited by the emitterbase junction capacitance.

Noncontact backscatter-mode near-infrared time-resolved imaging system: preliminary study for functional brain mapping

2006 ◽  
Vol 11 (5) ◽  
pp. 054006 ◽  
Author(s):  
Ichiro Sase ◽  
Akira Takatsuki ◽  
Junji Seki ◽  
Toshio Yanagida ◽  
Akitoshi Seiyama
Keyword(s):  
Brain Mapping ◽  
Near Infrared ◽  
Imaging System ◽  
Time Resolved ◽  
Functional Brain ◽  
Functional Brain Mapping ◽  
Preliminary Study ◽  
Time Resolved Imaging

scholarly journals Development of Near Infrared Time-Resolved Imaging System.

2001 ◽  
Vol 41 (supplement) ◽  
pp. S90
Author(s):  
I. Sase ◽  
H. Eda ◽  
A. Takatsuki ◽  
A Seiyama ◽  
T. Yanagida
Keyword(s):  
Near Infrared ◽  
Imaging System ◽  
Time Resolved ◽  
Time Resolved Imaging

Nanostructured Silver/Polystyrene Composite Film: Preparation and Ultrafast Third-Order Optical Nonlinearity

2002 ◽  
Vol 10 (4) ◽  
pp. 291-298 ◽  
Author(s):  
Rong Zeng ◽  
Shu Feng Wang ◽  
Hai Chun Liang ◽  
Min Zhi Rong ◽  
Ming Qiu Zhang ◽  
...  
Keyword(s):  
Optical Nonlinearity ◽  
Nanocomposite Films ◽  
Third Order ◽  
Nonlinear Optical Susceptibility ◽  
Time Resolved ◽  
Optical Susceptibility ◽  
Polystyrene Matrix ◽  
Micro Emulsion ◽  
Surface Modified ◽  
Effect Experiment

Surface-modified silver nanoparticles with various sizes, synthesized by water-in-oil micro-emulsion, were incorporated into polystyrene (PS) to form transparent nanocomposite films through solution-mixing and static-casting. It was found that the Ag nanoparticles could be re-dispersed well in the polymer matrix by using chloroform as a solvent due to a strong interaction between Ag and chloroform. XPS analysis suggested that there is no obvious interaction between nanosilver and the polystyrene matrix. The third-order nonlinear optical susceptibility of Ag/PS nanocomposite films is around 10-esu and increases with increasing particle size, as measured by the time-resolved femtosecond optical Kerr effect experiment at a wavelength of 830nm. The results demonstrate that the present fabrication approach can effectively tailor the structure and properties of the nanocomposites.

scholarly journals Real-time observation of tetrapyrrole binding to an engineered bacterial phytochrome

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Yusaku Hontani ◽  
Mikhail Baloban ◽  
Francisco Velazquez Escobar ◽  
Swetta A. Jansen ◽  
Daria M. Shcherbakova ◽  
...  
Keyword(s):  
Real Time ◽  
Rational Design ◽  
Near Infrared ◽  
Fluorescent Proteins ◽  
Covalent Bond ◽  
Binding Pocket ◽  
Tissue Imaging ◽  
Covalent Attachment ◽  
Time Resolved

AbstractNear-infrared fluorescent proteins (NIR FPs) engineered from bacterial phytochromes are widely used for structural and functional deep-tissue imaging in vivo. To fluoresce, NIR FPs covalently bind a chromophore, such as biliverdin IXa tetrapyrrole. The efficiency of biliverdin binding directly affects the fluorescence properties, rendering understanding of its molecular mechanism of major importance. miRFP proteins constitute a family of bright monomeric NIR FPs that comprise a Per-ARNT-Sim (PAS) and cGMP-specific phosphodiesterases - Adenylyl cyclases - FhlA (GAF) domain. Here, we structurally analyze biliverdin binding to miRFPs in real time using time-resolved stimulated Raman spectroscopy and quantum mechanics/molecular mechanics (QM/MM) calculations. Biliverdin undergoes isomerization, localization to its binding pocket, and pyrrolenine nitrogen protonation in <1 min, followed by hydrogen bond rearrangement in ~2 min. The covalent attachment to a cysteine in the GAF domain was detected in 4.3 min and 19 min in miRFP670 and its C20A mutant, respectively. In miRFP670, a second C–S covalent bond formation to a cysteine in the PAS domain occurred in 14 min, providing a rigid tetrapyrrole structure with high brightness. Our findings provide insights for the rational design of NIR FPs and a novel method to assess cofactor binding to light-sensitive proteins.

scholarly journals Interfacial Crystallization and Supramolecular Self-Assembly of Spider Silk Inspired Protein at the Water-Air Interface

Materials ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4239
Author(s):  
Pezhman Mohammadi ◽  
Fabian Zemke ◽  
Wolfgang Wagermaier ◽  
Markus B. Linder
Keyword(s):  
Self Assembly ◽  
Spider Silk ◽  
Assembly Process ◽  
Protein Solution ◽  
Time Resolved ◽  
Macromolecular Assembly ◽  
X Ray Scattering ◽  
Air Interface ◽  
Fundamental Research ◽  
Β Sheet

Macromolecular assembly into complex morphologies and architectural shapes is an area of fundamental research and technological innovation. In this work, we investigate the self-assembly process of recombinantly produced protein inspired by spider silk (spidroin). To elucidate the first steps of the assembly process, we examined highly concentrated and viscous pendant droplets of this protein in air. We show how the protein self-assembles and crystallizes at the water–air interface into a relatively thick and highly elastic skin. Using time-resolved in situ synchrotron X-ray scattering measurements during the drying process, we showed that the skin evolved to contain a high β-sheet amount over time. We also found that β-sheet formation strongly depended on protein concentration and relative humidity. These had a strong influence not only on the amount, but also on the ordering of these structures during the β-sheet formation process. We also showed how the skin around pendant droplets can serve as a reservoir for attaining liquid–liquid phase separation and coacervation from the dilute protein solution. Essentially, this study shows a new assembly route which could be optimized for the synthesis of new materials from a dilute protein solution and determine the properties of the final products.

scholarly journals Photoreactivity of Hair Melanin from Different Skin Phototypes—Contribution of Melanin Subunits to the Pigments Photoreactive Properties

2021 ◽  
Vol 22 (9) ◽  
pp. 4465
Author(s):  
Krystian Mokrzynski ◽  
Shosuke Ito ◽  
Kazumasa Wakamatsu ◽  
Theodore G. Camenish ◽  
Tadeusz Sarna ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Singlet Oxygen ◽  
Near Infrared ◽  
Paramagnetic Resonance ◽  
Time Resolved ◽  
W Band ◽  
Epr Oximetry ◽  
X Band ◽  
Hair Samples ◽  
Electron Paramagnetic

Photoreactivity of melanin has become a major focus of research due to the postulated involvement of the pigment in UVA-induced melanoma. However, most of the hitherto studies were carried out using synthetic melanin models. Thus, photoreactivity of natural melanins is yet to be systematically analyzed. Here, we examined the photoreactive properties of natural melanins isolated from hair samples obtained from donors of different skin phototypes (I, II, III, and V). X-band and W-band electron paramagnetic resonance (EPR) spectroscopy was used to examine the paramagnetic properties of the pigments. Alkaline hydrogen peroxide degradation and hydroiodic acid hydrolysis were used to determine the chemical composition of the melanins. EPR oximetry and spin trapping were used to examine the oxygen photoconsumption and photo-induced formation of superoxide anion, and time-resolved near infrared phosphorescence was employed to determine the singlet oxygen photogeneration by the melanins. The efficiency of superoxide and singlet oxygen photogeneration was related to the chemical composition of the studied melanins. Melanins from blond and chestnut hair (phototypes II and III) exhibited highest photoreactivity of all examined pigments. Moreover, melanins of these phototypes showed highest quantum efficiency of singlet oxygen photogeneration at 332 nm and 365 nm supporting the postulate of the pigment contribution in UVA-induced melanoma.

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