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Wideband optical frequency comb generation using a fiber re-circulating loop cascaded with a spectrum expander including highly nonlinear fiber

Wang F., Kang W.

Optica Applicata

2021

Vol. 51, nr 2

181--191

A wideband optical frequency comb (OFC) generator using a fiber re-circulating loop (FRL) including a phase modulator and optical amplifier, cascaded with a spectrum expander containing a high-power erbium-doped fiber amplifier and highly nonlinear fiber (HNLF) is proposed and experimentally demonstrated, in which the FRL is used as a source to generate seed comb lines, and then generated seed comb lines are extended to a wideband optical frequency comb using cascaded four-wave mixing in the HNLF. Only using one stage spectrum expander, a stable 20-GHz optical comb with 201 comb lines within 30-dB power deviation, spanning 40-nm bandwidth, is achieved. The results show that the HNLF has unique ability to broaden output spectrum from the FRL. In addition, an optical frequency comb is dramatically broadened, which may be predicted by optimizing gain and dispersion of the FRL or configuration of the spectrum expander, or both.

Massive Search for Spot- and Facula-Crossing Events in 1598 Exoplanetary Transit Light Curves

Baluev R. V., Sokov E. N., Sokova I. A., Shaidulin V. Sh., Veselova A. V., Aitov V. N., Mitiani G. Sh., Valeev A. F., Gadelshin D. R., Gutaev A. G., Beskin G. M., Valyavin G. G., Antonyuk K., Barkaoui K., Gillon M., Jehin E., Delrez L., Guðmundsson S., Dale H. A., Fernández-Lajús E., Di Sisto R. P., Bretton M., Wunsche A., Hentunen V.-P., Shadick S., Jongen Y., Kang W., Kim T., Pakštienė E., Qvam J. K. T., Knight C. R., Guerra P., Marchini A., Salvaggio F., Papini R., Evans P., Salisbury M., Garlitz J., Esseiva N., Ogmen Y., Bosch-Cabot P., Selezneva A., Hinse T. C.

Acta Astronomica

2021

Vol. 71, No. 1

25--53

We developed a dedicated statistical test for a massive detection of spot- and facula-crossing anomalies in multiple exoplanetary transit light curves, based on the frequentist p-value thresholding. This test was used to augment our algorithmic pipeline for transit light curves analysis. It was applied to 1598 amateur and professional transit observations of 26 targets being monitored in the EXPANSION project. We detected 109 statistically significant candidate events revealing a roughly 2:1 asymmetry in favor of spots-crossings over faculae-crossings. Although some candidate anomalies likely appear non-physical and originate from systematic errors, such asymmetry between negative and positive events should indicate a physical difference between the frequency of star spots and faculae. Detected spot-crossing events also reveal positive correlation between their amplitude and width, possibly due to spot size correlation. However, the frequency of all detectable crossing events appears just about a few per cent, so they cannot explain excessive transit timing noise observed for several targets.

Determination of the trace lead in seasoning samples with derivative hydride generation atomic absorption spectrometry

Liang S., Ha J., Sun H., Kang W., Sun J.

Chemia Analityczna

2003

Vol. 48, No. 4

723-732

A new method for the determination of lead traces in seasoning by derivative hydride generation atomic absorption spectrometry (D-HGAAS) has been developed. The conditions influencing the derivative absorbance of lead were evaluated and optimised. The detection limit and sensitivity of the proposed method were improved 8.8 times and 26 times, respectively in comparison to those of the conventional hydride generation atomic absorption spectrometry. The characteristic concentration of lead (referring to derivative absorbance of 0.0044) was 0.017 ug L(-1) at maximum sensitivity. The detection limit (3sigma) for lead in the real sample equalled 0.96 ng g(-1) for 5.0 g sample at maximum sensitivity. The method was applied to the determination of lead in seasoning samples with a recovery range of 92-103%.

Opracowano nową metodę oznaczania śladowych ilości ołowiu w przyprawach za pomocą pochodnej absorpcyjnej spektrometrii atomowej z generacją wodorków. Oszacowano i zoptymalizowano warunki wpływające na pochodną absorbancji ołowiu. Granica detekcji i czułość metody były lepsze odpowiednio 8.8 i 22 razy w porównaniu z konwencjonalną atomową spektrometrią absorpcyjną z generacją wodorków. Charakterystyczne stężenie (dla pochodnej absorbancji 0.0044) wynosiło 0.017 ng L(-1) przy maksymalnej czułości układu. Granca detekcji (3 Sigma) dla ołowiu w próbce rzeczywistej wynosiła 0.96 ng g(-1) (przy maksymalnej czułości układu i masie próbki 5.0 g). Metodę zastosowano do oznaczania ołowiu w przyprawach. Strwierdzono, że odzysk ołowiu waha się. w granicach 92-103%.