Wavelength Dependence in the Analysis of Carbon Content in Coal by Nanosecond 266 nm and 1064 nm Laser Induced Breakdown Spectroscopy

The wavelength dependence of laser induced breakdown spectroscopy （LIBS） in the analysis of the carbon contents of coal was studied using 266 nm and 1064 nm laser radiations. Compared with the 1064 nm wavelength laser ablation, the 266 nm wavelength laser ablation has less thermal effects, resulting in a better crater morphology on the coal pellets. Besides, the 266 nm wavelength laser ablation also provides better laser-sample coupling and less plasma shielding, resulting in a higher carbon line intensity and better signal reproducibility. The carbon contents in the bituminous coal samples have better linearity with the line intensities of atomic carbon measured by the 266 nm wavelength than those measured by the 1064 nm wavelength. The partial least square （PLS） model was established for the quantitative analysis of the carbon content in coal samples by LIBS. The results show that both of the 266 nm and 1064 nm wavelengths are capable of achieving good performance for the quantitative analysis of carbon content in coal using the PLS method.

Wavelength dependence of light propagation in a water suspension of anisotropic scatterers

We experimentally study the wavelength dependence of light propagation in a water suspension of lithium niobate microcrystalline particles.First,the ballistic transmission in the visible range of the suspension is measured.The nonlinear relationship is observed between the transport mean free path and the wavelength of the incident light.Secondly,we measure the coherent backscattering (CBS) of the sample at different wavelengths.The full width at half maximum of the CBS cone at 532 nm is about 1.24 times as large as that at 671 nm.The results indicate that the light with a long wavelength propagates further than the short wavelength light and the localization state of the short one is stronger.Finally,we investigate the light-controllable CBS experiments in the disordered materials of anisotropic scatterers,which show that the configuration of pump light with the longer wavelength and the probe light with the shorter wavelength performs better.

Wavelength dependent loss of splice of single-mode fibers

After reviewing three different definitions of mode field diameter of single-mode fibers, coupled efficiency calculation methods associated with lateral offset, longitude separation and wavelength, the effects produced by them, and the influences of splicing defects were discussed in detail. The regularities of the effects were studied according to the first order derivation of couple efficiency formula, and a simplified formula for couple efficiency calculation was presented under the circumstance of slight misalignment, with respect to wavelength, 2, and in a good agreement with the theoretical model. The simplified formula provides a new but simple approach to evaluate wavelength dependent couple efficiency of single-mode fibers. Theoretical analyses and numerical calculations show that, when those defects exist, the wavelength produces additional effects on the couple loss that growth of wavelength causes an increase on the couple efficiency for the lateral offset or longitude separation whereas lessens the couple efficiency due to angular misalignment or mode fields mismatching, and that the wavelength degrades the couple efficiency distinctly when λ≥2.5 μm whereas it distorts the couple slightly in range of λ≤2λ≤2 μm.

Polarization-Insensitive Silica on Silicon Arrayed Waveguide Grating Design

A new technology for fabrication of silica on silicon arrayed waveguide grating (AWG) based on deep etching and thermal oxidation is presented.Using this method,a silicon layer is remained at the side of waveguide.The stress distribution and effective refractive index of waveguide fabricated by this approach are calculated using finite element and finite difference beam propagation method,respectively.The results of these studies indicate that the stress of silica on silicon optical waveguide can be matched in parallel and vertical direction and AWG polarization dependent wavelength (PDλ) can be reduced effectively due to side-silicon layer.

A Versatile Tetraphenylethene Derivative Bearing Excitation Wavelength Dependent Emission,Multistate Mechanochromism,Reversible Photochromism,and Circularly Polarized Luminescence and Its Applications in Multimodal Anticounterfeiting

Multimodal anticounterfeiting has become increasingly challenging in modern society to guarantee information security and the safety of property.In this study,a versatile cholesterol-containing tetraphenylethene derivative is shown to have multiple optical properties,including stimuli-responsive fluorescence,reversible photochromism,excitation wavelength dependent luminescence,and circularly polarized luminescence.After the application of diverse processing methods(writing,screen painting,drawing,and pyrography),we found that this molecule can serve as an anticounterfeiting toolbox to provide rich anticounterfeiting effects through the synergistical use of multiple optical properties.This work offers important insight for designing novel small organic molecules for advanced multimodal anticounterfeiting technology.