Novel mid-infrared dispersive wave generation in gas-filled PCF by transient ionization-driven changes in dispersion

Gas-filled hollow-core photonic crystal fibre (PCF) is being used to generate ever wider supercontinuum spectra, in particular via dispersive wave (DW) emission in the deep and vacuum ultraviolet, with a multitude of applications. DWs are the result of the resonant transfer of energy from a self-compressed soliton, a process which relies crucially on phase matching. It was recently predicted that, in the strong-field regime, the additional transient anomalous dispersion introduced by gas ionization would allow phase-matched DW generation in the mid-infrared (MIR)-something that is forbidden in the absence of free electrons. Here we report for the first time the experimental observation of such MIR DWs, embedded in a 4.7-octave-wide supercontinuum that uniquely reaches simultaneously to the vacuum ultraviolet, with up to 1.7 W of total average power

Photoionization-Induced Emission of Tunable Few-Cycle Midinfrared Dispersive Waves in Gas-Filled Hollow-Core Photonic Crystal Fibers

We propose a scheme for the emission of few-cycle dispersive waves in the midinfrared using hollow-core photonic crystal fibers filled with noble gas. The underlying mechanism is the formation of a plasma cloud by a self-compressed, subcycle pump pulse. The resulting free-electron population modifies the fiber dispersion, allowing phase-matched access to dispersive waves at otherwise inaccessible frequencies, well into the midinfrared. Remarkably, the pulses generated turn out to have durations of the order of two optical cycles. In addition, this ultrafast emission, which occurs even in the absence of a zero dispersion point between pump and midinfrared wavelengths, is tunable over a wide frequency range simply by adjusting the gas pressure. These theoretical results pave the way to a new generation of compact, fiber-based sources of few-cycle midinfrared radiation

Cell-specific targeting of genetically encoded tools for neuroscience

Genetically encoded tools for visualizing and manipulating neurons in vivo have led to significant advances in neuroscience, in large part because of the ability to target expression to specific cell populations of interest. Current methods enable targeting based on marker gene expression, development, anatomical projection pattern, synaptic connectivity, and recent activity as well as combinations of these factors. Here, we review these methods, focusing on issues of practical implementation as well as areas for future improvement

Generation of broadband mid-IR and UV light in gas-filled single-ring hollow-core PCF

We report generation of an ultrafast supercontinuum extending into the mid-infrared in gas-filled single-ring hollow-core photonic crystal fiber (SR-PCF) pumped by 1.7 mu m light from an optical parametric amplifier. The simple fiber structure offers shallow dispersion and flat transmission in the near and mid-infrared, enabling the generation of broadband spectra extending from 270 nm to 3.1 mu m, with a total energy of a few mu J. In addition, we demonstrate the emission of ultraviolet dispersive waves whose frequency can be tuned simply by adjusting the pump wavelength. SR-PCF thus constitutes an effective means of compressing and delivering tunable ultrafast pulses in the near and mid-infrared spectral regions. (C) 2017 Optical Society of Americ

Analysis of genetic markers for the optimization of an individualized approach to osteoporosis.

Aim of this study: Osteoporosis is a systemic skeletal disease characterized by compromised bone structure and resistance and by an increased risk of fracture especially in postmenopausal women. Multiple factors including hormonal, environmental and genetic factors are involved in osteoporosis development and clinical outcome. It has been shown that Klotho and insulin-like growth factor-1 (IGF-1) have a significant effect on aging and osteoporosis risk. Actually, Insulin-like growth factor-1 (IGF-1) is a critical polypeptide that plays an important role in the regulation of bone metabolism, which promotes bone cell growth, differentiation, cell cycle progression. Klotho modulates aging in mice and humans, Klotho membrane-bound protein serves as a co-receptor required for the fibroblast growth factor 23 (FGF23), the link between Klotho and FGF23 creates a negative feedback that blocks the enzyme that converts 25-hydroxy Vitamin D to the active form (1,25 dihydroxy Vitamin D). Thus, klotho and FGF23 may function in a common signal transduction pathway in maintaining mineral ion homeostasis. Considering that some gene variant might influence production level and function of these mediators, we have started the evaluation of associations among IGF-1, IGF-1R and Klotho 1 SNPs and osteoporosis risk. Methods: In this preliminary approach, a total of 20 women with diagnosis of osteoporosis confirmed by radiograph or DEXA scan and a total of 72 healthy control women were included in the study. For the genetic analysis, peripheral blood samples were collected and genomic DNA was extracted from leukocytes. Genotypic analysis of polymorphisms of Klotho 1 (rs577912), IGF-1(rs35767), IGF-1R was conducted using a competitive allele specific PCR assays (KASpar) developed by Kbioscence. Genotype and allele frequencies were compared by statistical analysis using dominant, codominant, and recessive models. Results: In our study, the analysis of genotypic and allelic frequencies has highlighted, that IGF-I rs35767 genotypes positive for T allele are more represented in cases than in controls and could be associated with susceptibility to osteoporosis (P = 0.0327 OR= 4.529; 95% C.I.: 1.27 - 16.1). Instead, the SNP of Klotho 1 and IGF-I R have in our case subjects a frequency not different from that of the controls. Discussion and Conclusion: Our results are in full agreement with those from Zhang et al. (Genet Mol Res. 2015; 14: 7655-60) reporting association of T+ genotypes of rs35767 with lower BMD levels in the femoral neck. This preliminary result suggests that polymorphism in IGF-I rs35767 might play a role in osteoporosis risk and could be considered a potential indicator for risk of osteoporosis in postmenopausal women

Counterpropagating frequency mixing with terahertz waves in diamond

Frequency conversion by means of Kerr nonlinearity is one of the most common and exploited nonlinear optical processes in the UV, visible, IR, and mid-IR spectral regions. Here we show that wave mixing of an optical field and a terahertz wave can be achieved in diamond, resulting in the frequency conversion of the terahertz radiation either by sum-or difference-frequency generation. In the latter case, we show that this process is phase matched and most efficient in a counterpropagating geometry. (C) 2013 Optical Society of Americ

Counter-propagating difference-frequency generation in diamond with terahertz fields

The nonlinear interaction of terahertz (THz) pulses with optical fields in Kerr, gaseous media is a key ingredient for broadband THz detection schemes [1]. Terahertz field-induced second harmonic generation in solid-state media has also been considered for THz detection and as a tool e.g. for liquid dynamics investigations [2,3], while four-wave mixing has been addressed as a possible mechanism for THz generation [4,5]. © 2013 IEEE

Counter-propagating difference-frequency generation in diamond with terahertz fields

The nonlinear interaction of terahertz (THz) pulses with optical fields in Kerr, gaseous media is a key ingredient for broadband THz detection schemes [1]. Terahertz field-induced second harmonic generation in solid-state media has also been considered for THz detection and as a tool e.g. for liquid dynamics investigations [2,3], while four-wave mixing has been addressed as a possible mechanism for THz generation [4,5]

Counter-propagating difference frequency mixing in diamond with terahertz waves

We investigate four-wave mixing between terahertz and optical pulses in diamond. We observe the occurrence of sum and difference frequency generation, with the latter being phase-matched for terahertz pulses counter-propagating to the optical field. © 2013 The Optical Society