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high harmonic generation

Kuang-I Lin, Yen-Hung Ho, Shu-Bai Liu, Jian-Jhih Ciou, Bo-Ting Huang, Christopher Chen, Han-Ching Chang, Chien-Liang Tu, Chang-Hsiao Chen
Edge morphology and lattice orientation of single-crystal molybdenum disulfide (MoS2) monolayers, a transition metal dichalcogenide (TMD), possessing a triangular shape with different edges grown by chemical vapor deposition are characterized by atomic force microscopy and transmission electron microscopy. Multiphoton laser scanning microscopy is utilized to study one-dimensional atomic edges of MoS2 monolayers with localized mid-gap electronic states, which result in greatly enhanced optical second-harmonic generation (SHG)...
January 12, 2018: Nano Letters
Jian Zhang, Zhaofeng Ding, Cheng Tan, Kevin Huang, Oscar O Bernal, Pei-Chun Ho, Gerald D Morris, Adrian D Hillier, Pabitra K Biswas, Stephen P Cottrell, Hui Xiang, Xin Yao, Douglas E MacLaughlin, Lei Shu
The origin of the pseudogap region below a temperature T* is at the heart of the mysteries of cuprate high-temperature superconductors. Unusual properties of the pseudogap phase, such as broken time-reversal and inversion symmetry are observed in several symmetry-sensitive experiments: polarized neutron diffraction, optical birefringence, dichroic angle-resolved photoemission spectroscopy, second harmonic generation, and polar Kerr effect. These properties suggest that the pseudogap region is a genuine thermodynamic phase and are predicted by theories invoking ordered loop currents or other forms of intra-unit-cell (IUC) magnetic order...
January 2018: Science Advances
Christian Schlickriede, Naomi Waterman, Bernhard Reineke, Philip Georgi, Guixin Li, Shuang Zhang, Thomas Zentgraf
The abrupt phase change of light at metasurfaces provides high flexibility in wave manipulation without the need for accumulation of propagating phase through dispersive materials. In the linear optical regime, one important application field of metasurfaces is imaging by planar metalenses, which enables device miniaturization and aberration correction compared to conventional optical microlens systems. With the incorporation of nonlinear responses into passive metasurfaces, optical functionalities of metalenses are anticipated to be further enriched, leading to completely new application areas...
January 8, 2018: Advanced Materials
Dong Wang, Yuhuan Luo, Xiaoxin Wang, David J Orlicky, Komuraiah Myakala, Pengyuan Yang, Moshe Levi
Obesity and obesity related kidney and liver disease have become more prevalent over the past few decades, especially in the western world. Sodium-glucose cotransporter 2 (SGLT2) inhibitors are a new class of antidiabetic agents with promising effects on cardiovascular and renal function. Given SGLT2 inhibitors exert both anti-diabetic and anti-obesity effects by promoting urinary excretion of glucose and subsequent caloric loss, we investigated the effect of the highly selective renal SGLT2 inhibitor dapagliflozin in mice with Western diet (WD) induced obesity...
January 3, 2018: International Journal of Molecular Sciences
Zhuo Wang, Zhaogang Dong, Hai Zhu, Lei Jin, Ming-Hui Chiu, Lain-Jong Li, Qing-Hua Xu, Goki Eda, Stefan A Maier, Andrew T S Wee, Cheng-Wei Qiu, Joel K W Yang
Monolayer two-dimensional transition metal dichalcogenides (2D TMDCs) exhibit promising characteristics in miniaturized nonlinear optical frequency converters, due to their inversion asymmetry and large second-order nonlinear susceptibility. However, these materials usually have a very short light interaction lengths with the pump laser because they are atomically thin, such that second-harmonic generation (SHG) is generally inefficient. In this paper, we fabricate a judiciously structured 150-nm-thick planar surface consisting of monolayer tungsten diselenide and sub-20-nm-wide gold trenches on flexible substrates, reporting ~7000-fold SHG enhancement without peak broadening or background in the spectra as compared to WSe2 on as-grown sapphire substrates...
January 4, 2018: ACS Nano
Tatiana M Medvedeva, Marina V Sysoeva, Gilles van Luijtelaar, Ilya V Sysoev
PURPOSE: The organization of neural networks and the mechanisms, which generate the highly stereotypical for absence epilepsy spike-wave discharges (SWDs) is heavily debated. Here we describe such a model which can both reproduce the characteristics of SWDs and dynamics of coupling between brain regions, relying mainly on properties of hierarchically organized networks of a large number of neuronal oscillators. MODEL: We used a two level mesoscale model. The first level consists of three structures: the nervus trigeminus serving as an input, the thalamus and the somatosensory cortex; the second level of a group of nearby situated neurons belonging to one of three modeled structures...
December 13, 2017: Neural Networks: the Official Journal of the International Neural Network Society
Kirill Yu Spasibko, Denis A Kopylov, Victor L Krutyanskiy, Tatiana V Murzina, Gerd Leuchs, Maria V Chekhova
The rate of an n-photon effect generally scales as the nth order autocorrelation function of the incident light, which is high for light with strong photon-number fluctuations. Therefore, "noisy" light sources are much more efficient for multiphoton effects than coherent sources with the same mean power, pulse duration, and repetition rate. Here we generate optical harmonics of the order of 2-4 from a bright squeezed vacuum, a state of light consisting of only quantum noise with no coherent component. We observe up to 2 orders of magnitude enhancement in the generation of optical harmonics due to ultrafast photon-number fluctuations...
December 1, 2017: Physical Review Letters
Hiroyuki Oya, Phillip E Gander, Christopher I Petkov, Ralph Adolphs, Kirill V Nourski, Hiroto Kawasaki, Matthew A Howard, Timothy D Griffiths
Natural environments elicit both phase-locked and non-phase-locked neural responses to the stimulus in the brain. The interpretation of the BOLD signal to date has been based on an association of the non-phase-locked power of high-frequency local field potentials (LFPs), or the related spiking activity in single neurons or groups of neurons. Previous studies have not examined the prediction of the BOLD signal by phase-locked responses. We examined the relationship between the BOLD response and LFPs in the same nine human subjects from multiple corresponding points in the auditory cortex, using amplitude modulated pure tone stimuli of a duration to allow an analysis of phase locking of the sustained time period without contamination from the onset response...
December 21, 2017: NeuroImage
Ibrahim Abdelwahab, Gustavo Grinblat, Kai Leng, Yi Li, Xiao Chi, Andrivo Rusydi, Stefan A Maier, Kian Ping Loh
2D hybrid organic-inorganic Ruddlesden-Popper perovskites (RPPs) have attracted considerable attention due to their rich photonic and optoelectronic properties. The natural multi-quantum-wells (MQWs) structure of 2D RPPs has been predicted to exhibit a large third-order nonlinearity. However, nonlinear optical studies on 2D RPPs have previously been conducted only on bulk polycrystalline samples, in which only weak third-harmonic generation (THG) was observed. Here, we perform parametric nonlinear optical characterization of 2D perovskite nanosheets mechanically exfoliated from four different lead halide RPP single crystals, from which we observe ultra-strong THG with a maximum effective third-order susceptibility (χ(3)) of 1...
December 20, 2017: ACS Nano
Ling Yuting, Chunhui Li, Kanheng Zhou, Guangying Guan, Paul L Appleton, Stephen Lang, David McGloin, Zhihong Huang, Ghulam Nabi
Photonics, especially optical coherence elastography (OCE) and second harmonic generation (SHG) imaging are novel high-resolution imaging modalities for characterization of biological tissues. Following our preliminary experience, we hypothesized that OCE and SHG imaging would delineate the microstructure of prostate tissue and aid in distinguishing cancer from the normal benign prostatic tissue. Furthermore, these approaches may assist in characterization of the grade of cancer, as well. In this study, we confirmed a high diagnostic accuracy of OCE and SHG imaging in the detection and characterization of prostate cancer for a large set of biopsy tissues obtained from men suspected to have prostate cancer using transrectal ultrasound (TRUS)...
December 18, 2017: Laboratory Investigation; a Journal of Technical Methods and Pathology
E A Migal, F V Potemkin, V M Gordienko
We have developed a robust optical parametric amplifier (OPA) based on three-AgGaS2-crystal pumping by a Cr:Forsterite GW femtosecond laser system, generating 150 fs pulses in dual bands of 1.6-2.0 μm (signal wave) and 3.5-5.5 μm (idler wave). By introducing a negative prechirp to the pump, a combined efficiency in two waves of greater than 10% was achieved, with signal energy up to 110 μJ and idler energy up to 43 μJ. Operation parameters of the system (intensity up to 90  TW/cm2) make OPA a promising tool for driving nonlinear optical phenomena, including generation of optical harmonics and laser-induced extreme states of matter in solids and liquids...
December 15, 2017: Optics Letters
F Labaye, M Gaponenko, V J Wittwer, A Diebold, C Paradis, N Modsching, L Merceron, F Emaury, I J Graumann, C R Phillips, C J Saraceno, C Kränkel, U Keller, T Südmeyer
We demonstrate a compact extreme ultraviolet (XUV) source based on high-harmonic generation (HHG) driven directly inside the cavity of a mode-locked thin-disk laser oscillator. The laser is directly diode-pumped at a power of only 51 W and operates at a wavelength of 1034 nm and a 17.35 MHz repetition rate. We drive HHG in a high-pressure xenon gas jet with an intracavity peak intensity of 2.8×1013  W/cm2 and 320 W of intracavity average power. Despite the high-pressure gas jet, the laser operates at high stability...
December 15, 2017: Optics Letters
François Risoud, Camille Lévêque, Marie Labeye, Jérémie Caillat, Alfred Maquet, Pascal Salières, Richard Taïeb, Tahir Shaaran
High harmonic spectroscopy gives access to molecular structure with Angström resolution. Such information is encoded in the destructive interferences occurring between the harmonic emissions from the different parts of the molecule. By solving the time-dependent Schrödinger equation, either numerically or with the molecular strong-field approximation, we show that the electron dynamics in the emission process generally results in a strong spectral smoothing of the interferences, blurring the structural information...
December 11, 2017: Scientific Reports
Man-Rong Li, Emma E McCabe, Peter W Stephens, Mark Croft, Liam Collins, Sergei V Kalinin, Zheng Deng, Maria Retuerto, Arnab Sen Gupta, Haricharan Padmanabhan, Venkatraman Gopalan, Christoph P Grams, Joachim Hemberger, Fabio Orlandi, Pascal Manuel, Wen-Min Li, Chang-Qing Jin, David Walker, Martha Greenblatt
Double corundum-related polar magnets are promising materials for multiferroic and magnetoelectric applications in spintronics. However, their design and synthesis is a challenge, and magnetoelectric coupling has only been observed in Ni3TeO6 among the known double corundum compounds to date. Here we address the high-pressure synthesis of a new polar and antiferromagnetic corundum derivative Mn2MnWO6, which adopts the Ni3TeO6-type structure with low temperature first-order field-induced metamagnetic phase transitions (T N = 58 K) and high spontaneous polarization (~ 63...
December 11, 2017: Nature Communications
David P Shelton
Long-range ion-induced correlations between water molecules have been observed by second-harmonic or hyper-Rayleigh scattering experiments with conflicting results. The most recent work observed a large difference between the results for H2O and D2O, and large discrepancies with the previously proposed theory. However, the present observations are in quantitative agreement with the model where the ion electric field induces second harmonic generation by the water molecules, and ion-ion correlations given by the Debye-Huckel theory account for intensity saturation at high ion concentration...
December 7, 2017: Journal of Chemical Physics
Zijian Cui, Dean Liu, Lailin Ji, Mingying Sun, Jie Miao, Jianqiang Zhu
Aiming at high-power laser frequency conversion, we present a new scheme that can self-compensate for the thermally induced phase mismatch. The basic design of the scheme is that three crystals with the same type are cascaded, of which the crystals at both ends are used for frequency conversion and the middle crystal is used for compensating phase mismatch. By configuring the polarization states of the interacting waves in the middle crystal, the sign of the first temperature derivative of the phase mismatch is opposite to that of the frequency conversion crystals...
November 27, 2017: Optics Express
Richard Wolf, Ingo Breunig, Hans Zappe, Karsten Buse
We demonstrate cascaded Stimulated Raman Scattering (SRS), Second-Harmonic Generation (SHG), and Sum-Frequency Generation (SFG) in integrated on-chip whispering-gallery resonators (WGRs). These lithium niobate-based WGRs are fabricated using highly-parallel semiconductor manufacturing techniques coupled with specialized polishing as a post-processing step and thus represent a novel means for batch fabrication of this family of non-linear devices. We achieved record high Q-factors for on-chip lithium niobate WGRs reaching up to 3 × 106...
November 27, 2017: Optics Express
Hong Chen, Pei-Fei Liu, Bing-Xuan Li, Hua Lin, Li-Ming Wu, Xin-Tao Wu
New middle and far-infrared (MFIR) nonlinear optical (NLO) chalcogenides have been receiving increasing attention for their great importance in military and civil fields. In addition, the current challenge in the efforts for identifying a promising MFIR NLO material lies in achieving simultaneously large second-harmonic generation (SHG) intensity and high laser-induced damage threshold (LIDT) in the same material. In this study, two quaternary non-centrosymmetric (NCS) sulfides, BaAg2GeS4 (1) and BaAg2SnS4 (2), were synthesized from a high-temperature solid-state reaction using BaCl2 flux in evacuated closed silica tubes...
December 8, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
C R McDonald, K S Amin, S Aalmalki, T Brabec
We investigate theoretically the effect of quantum confinement on high harmonic generation (HHG) in semiconductors by systematically varying the width of a model quantum nanowire. Our analysis reveals a reduction in ionization and a concurrent growth in HHG efficiency with increasing confinement. The drop in ionization results from an increase in the band gap due to stronger confinement. The increase in harmonic efficiency comes as a result of the confinement restricting the spreading of the transverse wave packet...
November 3, 2017: Physical Review Letters
Hongtao Hu, Na Li, Peng Liu, Ruxin Li, Zhizhan Xu
The first high harmonic spectrum containing only the odd orders was observed in experiments 30 years ago. However, a spectrum containing pure even harmonics has never been observed. We investigate the generation of pure even harmonics from oriented CO molecules in linearly polarized laser fields employing the time-dependent density-functional theory. We find that the even harmonics, with no odd orders, are generated with the polarization perpendicular to the laser polarization when the molecular axis of CO is perpendicular to the laser polarization...
October 27, 2017: Physical Review Letters
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