Laser Damage Mechanisms of Amorphous Ta2O5 Films at 1064, 532 and 355nm in One-on-One Regime

Ta2O5 films are deposited on fused silica substrates by conventional e-beam evaporation. Surface topography and chemical composition are examined by atomic force microscopy （AFM） and x-ray photoelectron spectroscopy （XPS）. The calculation of electron structures of Ta2O5 and Ta2O5-x is attempted using a first-principle pseudopotential method within the local density approximation. The laser-induced damage threshold （LIDT） is performed at 1064, 532 and 355 nm in 1-on-1 regime, respectively. The results show that the LIDT increases with the wavelength increasing, which is in agreement with the wavelength effect. However, the LIDT results are not consistent with the empirical equation （I（λ）=aλm）, which may be attributed to the intrinsic absorption of Ta2O5 at the wavelengths of 532 or/and 355 nm. Moreover, different damage morphologies are observed when the films are irradiated at different wavelengths. It is concluded that the laser damage at 1064 nm is the defect dominant mechanism and at 355 nm it is the intrinsic absorption dominant mechanism, whereas at 532 nm it is the combined defect and intrinsic absorption dominant mechanism.     

Comparison of laser-induced damage in Ta2O5 and Nb2O5 single-layer films and high reflectors

Ta2O5 and Nb2O5 films are deposited on BK7 glass substrates using an electron beam evaporation method and are annealed at 673 K in the air.In this letter,comparative studies of the optical transmittance,microstructure,chemical composition,optical absorption,and laser-induced damage threshold(LIDT) of the two films are conducted.Findings indicate that the substoichiometric defect is very harmful to the laser damage resistance of Ta2O5 and Nb2O5 films.The decrease of absorption improves the LIDT in films deposited by the same material.However,although the absorption of the Ta2O5 single layer is less than that of the Nb2O5 single layer,the LIDT of the former is lower than that of the latter.High-reflective(HR) coatings have a higher LIDT than single layers due to the thermal dissipation of the SiO2 layers and the decreased electric field intensity(EFI).In addition,the Nb2O5 HR coating achieves the highest LIDT at 25.6 J/cm 2 in both single layers and HR coatings.     

Study on the impedance of aligned carbon microcoils embedded in silicone rubber matrix

This paper reports that carbon microcoils are grown through a chemical vapour deposit process, they are then embedded in silicone rubber, and manipulated to parallel with each other along their axes in the resulting composite. The impedance |Z| as well as phase angle θ of both the original carbon microcoil sheets and the aligned carbon microcoil/silicone rubber composites are measured. The results illustrate that carbon microcoils in different forms show different alternating current electric properties. The aligned carbon microcoils in the composites show stable parameters for f<10⁴ Hz but a sharp decrease in both |Z| and θ for frequencies >10⁴ Hz, which will also change as the carbon microcoils are extended. But, the original sheets have a pure resistance with their parameters stable throughout the entire alternating current frequency range investigated.     

复合碱媒介法合成棒状CdTe晶体

以Te粉和Cd(NO₃)₂为原料, 以联胺为还原剂, 采用复合氢氧化物媒介法, 在不同的反应条件下分别合成了棒状和立方体状的CdTe晶体, 其中棒状CdTe晶体的横向尺度为2～3 μm, 纵向尺度达几十微米. 选择反应温度为180 ℃并在反应体系中适量加水, 将有助于棒状CdTe的形成, 并提出了CdTe晶体的生长模型. X射线衍射图谱(XRD)以及紫外-可见分光吸收谱测试表明, 合成的棒状CdTe结晶性好, 吸收峰值位于近红外, 能带带隙值约为1.49 eV.