Intrinsic polarization conversion and avoided-mode crossing in X-cut lithium niobate microrings

Compared with well-developed free space polarization converters, polarization conversion between TE and TM modes in waveguide is generally considered to be caused by shape birefringence, like curvature, morphology of waveguide cross section and scattering. Here, we reveal a hidden polarization conversion mechanism in X-cut lithium niobate microrings, that is the conversion can be implemented by birefringence of waveguides, which will also introduce an unavoidable avoided-mode crossing. In the experiment, we find that this mode crossing results in severe suppression of one sideband in local nondegenerate four-wave mixing and disrupts the cascaded four-wave mixing on this side. Simultaneously, we proposed, for the first time to our best knowledge, one two-dimensional method to simulate the eigenmodes (TE and TM) in X-cut microrings, which avoids the obstacle from large computational effort in three-dimensional anisotropic microrings simulation, and the mode crossing point. This work will provide an entirely novel approach to the design of polarization converters and simulation for monolithic photonics integrated circuits, and may be helpful to the studies of missed temporal dissipative soliton formation in X-cut lithium niobate rings

Media 1: Wave propagation in deep-subwavelength mode waveguides

Originally published in Optics Letters on 15 July 2012 (ol-37-14-2826

Media 2: Great optical buffering capacity for optical delay line and extraordinary optical reflection and mode conversion with extremely weak dielectric perturbations based on circular Bragg resonators

Originally published in JOSA B on 01 August 2012 (josab-29-8-2053

Media 1: Great optical buffering capacity for optical delay line and extraordinary optical reflection and mode conversion with extremely weak dielectric perturbations based on circular Bragg resonators

Originally published in JOSA B on 01 August 2012 (josab-29-8-2053

Media 2: Wave propagation in deep-subwavelength mode waveguides

Originally published in Optics Letters on 15 July 2012 (ol-37-14-2826

Bright Multicolored Photoluminescence of Hybrid Graphene/Silicon Optoelectronics

Graphene does not possess a band gap, and hot carrier relaxation in graphene is an ultrafast processs. This leads to a very low emission efficiency of graphene. We demonstrate bright multicolored frequency-upconverted photoluminescence from graphene via three-photon absorption by femtosecond laser injection at a communication wavelength 1.57 μm. The broadband and multiwavelength emission from graphene is based on the model of ultrafast electron–hole pair recombination and asymmetrical energized electron–hole radiation recombination in graphene. Furthermore, we show photoluminescence variation with blue light emission in the graphene/silicon hybrid system, with 2–3 orders of emission efficiency increase. The results demonstrate hot carrier multiplication and hot carrier scattering in graphene and could help to study the population inversion and broadband lasing of graphene

Animate field of 1.1THz

The broadband mechanism in the high-frequency band results from the coupling of Mie resonances in dielectric wires excited by the incident wave to the graphene plasmon resonances. In this visualization, we take the animate field of 1.1 THz for example to show the absorption process

Plasma metabolomics reveals membrane lipids, aspartate/asparagine and nucleotide metabolism pathway differences associated with chloroquine resistance in <i>Plasmodium vivax</i> malaria

<div><p>Background</p><p>Chloroquine (CQ) is the main anti-schizontocidal drug used in the treatment of uncomplicated malaria caused by <i>Plasmodium vivax</i>. Chloroquine resistant <i>P</i>. <i>vivax</i> (PvCR) malaria in the Western Pacific region, Asia and in the Americas indicates a need for biomarkers of resistance to improve therapy and enhance understanding of the mechanisms associated with PvCR. In this study, we compared plasma metabolic profiles of <i>P</i>. <i>vivax</i> malaria patients with PvCR and chloroquine sensitive parasites before treatment to identify potential molecular markers of chloroquine resistance.</p><p>Methods</p><p>An untargeted high-resolution metabolomics analysis was performed on plasma samples collected in a malaria clinic in Manaus, Brazil. Male and female patients with <i>Plasmodium vivax</i> were included (n = 46); samples were collected before CQ treatment and followed for 28 days to determine PvCR, defined as the recurrence of parasitemia with detectable plasma concentrations of CQ ≥100 ng/dL. Differentially expressed metabolic features between CQ-Resistant (CQ-R) and CQ-Sensitive (CQ-S) patients were identified using partial least squares discriminant analysis and linear regression after adjusting for covariates and multiple testing correction. Pathway enrichment analysis was performed using Mummichog.</p><p>Results</p><p>Linear regression and PLS-DA methods yielded 69 discriminatory features between CQ-R and CQ-S groups, with 10-fold cross-validation classification accuracy of 89.6% using a SVM classifier. Pathway enrichment analysis showed significant enrichment (<i>p</i><0.05) of glycerophospholipid metabolism, glycosphingolipid metabolism, aspartate and asparagine metabolism, purine and pyrimidine metabolism, and xenobiotics metabolism. Glycerophosphocholines levels were significantly lower in the CQ-R group as compared to CQ-S patients and also to independent control samples.</p><p>Conclusions</p><p>The results show differences in lipid, amino acids, and nucleotide metabolism pathways in the plasma of CQ-R versus CQ-S patients prior to antimalarial treatment. Metabolomics phenotyping of <i>P</i>. <i>vivax</i> samples from patients with well-defined clinical CQ-resistance is promising for the development of new tools to understand the biological process and to identify potential biomarkers of PvCR.</p></div

10-fold cross-validation analysis using clinical variables and top discriminatory metabolic features.

<p>10-fold cross-validation classification accuracies varied from 65% to 89.6% using platelet count, glycerophosphocholines, top 10, top 30, and all 69 discriminatory features. The average permuted accuracies (N = 1000 permutations) varied from 55–58%.</p

Identification of metabolic features associated with CQ resistance.

<p>A) Type 1 Manhattan plot, -log₁₀ <i>p</i> vs mass-to-charge. 81 <i>m/</i>z features with a broad range of <i>m/z</i> were found significant at FDR 0.20 threshold. Green dots represent the features that were up-regulated in the CQ-Resistant group and the red dots represent the features that were higher in the CQ-Sensitive group; B) Type 2 Manhattan plot, -log₁₀ <i>p</i> vs retention time, Majority of features had retention time greater than 4 minutes, which is consistent with elution profile of lipids on a C18 column; C) Two-way hierarchical clustering analysis using discriminatory features; D) Mummichog enriched pathways.</p