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摘要

Carbon is hard to be sensitively detected in laser-induced breakdown spectroscopy (LIBS). The optical emission can be significantly enhanced by resonantly exciting CN radicals in the plasma center using LIBS assisted with laser-induced fluorescence (LIBS-LIF). However, the nitrogen source for CN formation is provided by ambient gas. Therefore, we propose a new approach of perip

PDF全文 Chinese Optics Letters | 2020,18(08):083001
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摘要

This study provides a rapid method for quantification of mineral oil in rapeseed oil using near-infrared spectroscopy. The data were processed by direct orthogonal signal correction (DOSC), successive projections algorithm (SPA), partial least squares, and principal component regression (PCR). Good correlation coefficients (R) of 0.998 and root-mean-squared error (RMSE)

PDF全文 Chinese Optics Letters | 2020,18(04):043001
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摘要

Spontaneous optical emission properties of laser-produced plasma during laser damage events at input and exit surfaces of fused silica were retrieved and compared. We show that plasma at the input surface is much larger in size and exhibits significantly higher electron number density and excitation temperature, even when smaller laser energy was used. This effect was attribute

PDF全文 Chinese Optics Letters | 2019,17(12):123002
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摘要

We demonstrate a novel type of miniature spectrometer based on a Fourier transform spectrometer (FTS) chip with a dense output array and a commercial photodetector (PD) array. The FTS chip has an output array cycle of 20 μm and consists of 51 Mach–Zehnder interferometers (MZIs), and the PD array is a commercial linear charged coupled device (CCD). An achromatic triplet lens i

PDF全文 Chinese Optics Letters | 2019,17(12):123001
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An experimental investigation of two-color polarization spectroscopy (TCPS) is presented based on the cesium 6S1/2 – 6P3/2 – 8S1/2 (852.3 nm + 794.6 nm) ladder-type system in a room-temperature vapor cell. The dependency of line shapes of TCPS on the power of a 852.3 nm pump and a 794.6 nm probe laser is measured in detail, and we confirm that

PDF全文 Chinese Optics Letters | 2019,17(09):093001
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摘要

High-resolution frequency-domain spectroscopy (FDS) is set up using a coherent and continuous wave terahertz (THz) emitter and receiver. THz waves are generated and detected by two photomixers with two distributed feedback (DFB) lasers. Atmospheric water vapor with different relative humidity is systematically investigated by the FDS. A high-frequency resolution of ~14 MHz is

PDF全文 Chinese Optics Letters | 2019,17(07):073001
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摘要

We present a specific-window method to subtract the interference of water vapor on terahertz frequency-domain spectroscopy (THz-FDS) at ambient temperature and pressure. A continuous-wave spectrometer based on photomixing was utilized to obtain THz-FDS of methanol vapor in the range of 50–1200 GHz. The distinctly spaced absorption features in the neighborhood of atmospheric wi

PDF全文 Chinese Optics Letters | 2018,16(10):103001
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The intensities of fluorescence spectral lines of Ca atoms and Sr atoms in two different hollow cathode lamps (HCLs) are measured by element-balance-detection technology. In the wavelength range of 350–750 nm in the visible spectral region, using the individual strongest line (Ca 422.67 nm, Sr 460.73 nm) as the bench mark, the population ratios between the excited states of Ca

PDF全文 Chinese Optics Letters | 2018,16(03):033001
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摘要

Using a measurement system based on fluorescence induced by variable pulse light, photosynthesis parameters of chlorella pyrenoidosa are obtained, employing single-turnover and multiple-turnover protocols under dark-adapted and light-adapted conditions. Under the light-adapted condition, σPSII′ is larger, and Fv′/Fm(ST)′ and Fv′/Fm(MT)′ are smaller than those of the dark-

PDF全文 Chinese Optics Letters | 2018,16(01):013001
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In this Letter, a miniature wearable Raman spectroscopy system is developed. A wearable fiber-optic probe is employed to help the stable and convenient collection of Raman spectra. A nonlinear partial least squares model based on a multivariate dominant factor is employed to predict the glucose level. The mean coefficients of determination are 0.99, 0.893, and 0.844 for the glu

PDF全文 Chinese Optics Letters | 2017,15(08):083001
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