Effect of Fe impurity on the optical loss of Nd-doped phosphate laser glass

The optical loss coefficient at 1053-nm wavelength, influenced by Fe ions in N31-type Nd-doped phosphate laser glass, was determined precisely and analyzed in detail. It is found that the optical loss coefficient per unit of Fe concentration (cm^(-1)/ppmw) increases with Fe concentration in the range of 0---300 ppmw, but it approaches a constant as the Fe concentration is larger than 300 ppmw. Such a concentration effect is due to a shift in the redox equilibrium between Fe3+ and Fe2+ ions in the glass. The effect of oxygen pressure, temperature, and variable valence states of other metal ions in glass samples on the optical loss is also discussed.

Influence of annealing temperature on structure, optical loss and laser-induced damage threshold of TiO2 thin films

TiO2 thin films are prepared on fused silica with conventional electron beam evaporation deposition. After annealed at different temperatures for 4h, the spectra and XRD patterns of the TiO2 thin film are obtained. Weak absorption of coatings is measured by the surface thermal lensing technique, and laser-induced damage threshold (LIDT) is determined. It is found that with the increasing annealing temperature, the transmittance of TiO2 films decreases. Especially when coatings are annealed at high temperature over 1173K, the optical loss is very serious. Weak absorption detection indicates that the absorption of coatings decreases firstly and then increases, and the absorption and defects play major roles in the LIDT of TiO2 thin films.

Investigation on microstructure and optical properties of titanium dioxide coatings annealed at various temperature

TiO2 coatings were prepared on fused silica with conventional electron beam evaporation deposition. After TiO2 thin films were annealed at different temperatures for 4 h, several properties were investigated by X-ray diffraction (XRD), spectrometer.. photoelectron spectroscopy (XPS) and AFM. It was found that with the annealing temperature increasing, the transmittance of TiO2 coatings decreased, and the cutoff wavelength shifted to long wavelength in near ultraviolet band. Especially, when coatings were annealed at high temperature, the optical loss is very serious, which can be attributed to the scattering and the absorption of TiO2 coatings. XRD patterns revealed that only anatase phase was observed in TiO2 coatings regardless of the different annealing temperatures. XPS results indicated that the fine chemical shift of TiO2 2p(1/2) should be attributed to existence of oxygen vacancies around Ti+4 ion. The investigation on surface morphology by AFM showed that the RMS of titania thin films gradually increases from less than 0.40 nm to 5.03 nm and it should be ascribed to the growth of titanium dioxide grain size with the increase of annealing temperature. (C) 2005 Elsevier B.V. All rights reserved.

Measurement of the optical transmission modes and losses of the poled guest-host polymer NAEC/PEK-c planar waveguides

The polyetherketone (PEK-c) guest-host polymer planar waveguides doped with (4'-nitro)-3-azo-9-ethyl-carbazole (NAEC) were prepared. The waveguide films were poled by corona-onset poling at elevated temperature (COPET), and the corona poling setup includes a grid voltage making the surface-charge distribution uniform. By using the prism-in coupling method, the dark-line spectrum given by the reflected intensity versus the angle of incidence have been obtained, and the optical transmission losses of mth modes have been measured for the poled polymer waveguides at lambda = 632.8 nm. The measurement result showed that the optical loss of the fundamental mode is less than 0.7 dB cm(-1) for the TE polarization. (C) 2000 Elsevier Science Ltd. All rights reserved.

铒镱共掺磷酸盐玻璃的激光性质

制备了镱铒共掺的磷酸盐玻璃并研究了室温下LD泵浦的连续激光输出性质。在泵浦功率为496mW时实现了最大输出功率77mW。讨论了在不同玻璃样品厚度和谐振腔长度时的斜率效率的变化以及在不同玻璃样品厚度，泵浦功率和谐振腔长度时的不同激光模式竞争的动力学行为。结果表明：激光光谱受到光学增益和光学损耗相对大小的限制。

Growth of composite sapphire/Ti : sapphire by the hydrothermal method

Composite sapphire/Ti:sapphire crystals for high-power laser application were grown by the hydrothermal method. The results of the X-ray rocking curve analysis indicate high crystalline quality of the surface Al2O3 material. The strong bonding between the overgrown Al2O3 and seed Ti:Al2O3 crystals is indispensable for withstanding high thermal stresses produced by intense optical pumping. The optical loss at the boundary of the composite crystal is considerably low, indicating the lack of scattering centers. (c) 2005 Elsevier B.V. All rights reserved.

水热法生长复合钛宝石激光晶体

水热法生长了复合钛宝石(Al2O3／Ti：Al2O3)激光晶体．对外层Al2O3X射线ω扫描表明其晶体质量很高．外层生长的Al2O3和内部的钛宝石激光棒结合牢固、紧密，因而能适应高强度泵浦所带来的激光介质内部的热应力．复合激光晶体界面层带来的光损耗很小．就我们所知，这是首次用水热法生长复合激光晶体．

退火对电子束热蒸发193nm Al2O3/MgF2反射膜性能的影响

设计并镀制了193nm Al2O3/MgF2反射膜,对它们在空气中分别进行了250-400℃的高温退火,测量了样品的透射率光谱曲线和绝对反射率光谱曲线.发现样品在高反射区的总的光学损耗随退火温度的升高而下降,而后趋于饱和.采用总积分散射的方法对样品在不同退火温度下的散射损耗进行了分析,发现随着退火温度的升高散射损耗有所增加.因此,总的光学损耗的下降是由于吸收损耗而不是散射损耗起主导作用.对Al2O3材料的单层膜进行了同等条件的退火处理,由它们光学性能的变化推导出它们的折射率和消光系数的变化,从而解释了相应

Annealing effects on electron-beam evaporated Al2O3 films

The effects of post-deposited annealing on structure and optical properties of electron-beam evaporated Al2O3 single layers were investigated. The films were annealed in air for 1.5 h at different temperatures from 250 to 400 degrees C. The optical constants and cut-off wavelength were deduced. Microstructure of the samples was characterized by X-ray diffraction (XRD). Profile and surface roughness measurement instrument was used to determine the rms surface roughness. It was found that the cut-off wavelength shifted to short wavelength as the annealing temperature increased and the total optical loss decreased. The film structure remained amorphous even after annealing at 400 degrees C temperature and the samples annealed at higher temperature had the higher rms surface roughness. The decreasing total optical loss with annealing temperature was attributed to the reduction of absorption owing to oxidation of the film by annealing. Guidance to reduce the optical loss of excimer laser mirrors was given. (c) 2004 Elsevier B.V. All rights reserved.

退火对电子束热蒸发Al2O3薄膜性能影响的实验研究

用电子束热蒸发方法镀制了Al2O3材料的单层膜，对它们在空气中进行了250～400℃的高温退火。对样品的透射率光谱曲线进行了测量，计算了样品的消光系数、折射率和截止波长。通过X射线衍射仪(XRD)测量分析了薄膜的微观结构，采用表面轮廓仪测量了样品的表面均方根粗糙度。结果发现随着退火温度的提高光学损耗下降，薄膜结构在退火温度为400℃时仍然为无定形态，样品的表面粗糙度随退火温度的升高而增加。引起光学损耗下降起主导作用的是吸收而不是散射，吸收损耗的下降主要是由于退火使材料吸收空气中的氧而进一步氧化，从而使薄膜

沉积温度对热舟蒸发MgF2薄膜性能的影响

采用热舟蒸发方法沉积了氟化镁（MgF2）材料的单层膜，沉积温度从200℃上升到350℃，间隔为50℃。测量了样品的透射率和反射率光谱曲线，进行了表面粗糙度的标定，并在此基础上进行了光学损耗及散射损耗的计算。同时对355nm波长处的激光诱导损伤阈值进行了测量。结果表明：随着沉积温度的升高，光学损耗增加;在短波长范围散射损耗在光学损耗中所占比例很小，光学损耗的增加主要由吸收损耗引起；在355nm波长处的损伤阈值变化与吸收损耗的变化趋势相关，损伤机制主要是吸收起主导作用。样品的微缺陷密度也是影响损伤阈值的一个重要因素，损伤阈值随缺陷密度的增加而降低。

热舟蒸发LaF_3薄膜的紫外性能研究

研究了沉积温度对热舟蒸发氟化镧薄膜结构和光学性能的影响,沉积温度从200℃上升到350℃,间隔为50℃.采用分光光度计测量了样品的透射率和反射率光谱曲线,并在此基础上进行了光学损耗、光学常数以及带隙和截止波长的计算.采用表面轮廓仪进行了表面形貌和表面粗糙度的标定,采用X射线衍射(XRD)方法测量了不同沉积温度下样品的微结构.发现在短波长波段,随着沉积温度的升高,光学损耗增加,晶粒尺寸增大,表面粗糙度略有增加.不过散射损耗在光学损耗中所占比例均很小,光学损耗的增加主要由吸收损耗引起.随着沉积温度的升高,折射率与消光系数增大,带隙变小,相对应的截止波长向长波方向移动.

低损耗193nm增透膜

计算了适用于193nm增透膜设计与制备的基底与薄膜材料的光学常数,并在此基础上对193nm增透膜进行了设计、制备与性能分析.发现基底材料的吸收损耗对增透膜元件的影响很大,超过一定值时,增透膜元件的设计透过率将达不到理想水平.对单面增透膜的设计与制备结果表明,当吸收损耗降低到一定程度,散射损耗成为不可忽略的因素.采用热舟蒸发方法实现了性能良好的193nm减反射膜,剩余反射率在0.2%以下.

Investigation on thermal stability of TiO2 films for application at high temperature

The thermal stability of electron beam deposited TiO2 monolayers and TiO2/SiO2 high reflectors (HR) during 300 to 1100 degrees C annealing is studied. It is found that the optical loss of film increases with the increase in annealing temperature, due to the phase change, crystallisation and deoxidising of film. Scattering loss dominates the optical property degradation of film below 900 degrees C, while the absorption is another factor at 1100 degrees C. The increase in refractive index and decrease in physical thickness of TiO2 layer shift the spectra of HR above 900 degrees C. The possible crack mechanism on the surface of HR during annealing is discussed. Guidance for application on high temperature stable optical coatings is given.

Design and analysis of 1.3 mu m GaAs-based quantum dot vertical-cavity surface-emitting lasers

A theoretical study on 1.3 mu m GaAs-based quantum dot vertical-cavity surface-emitting lasers (VCSELs) was made. Investigation of the influence of VCSELs on the optical confinement factors and the optical loss and the calculation of the material gain of the assembled InGaAs/GaAs quantum dots. Analysis of the threshold characteristic was made and the multi-wavelength cavity and multilayer quantum-dot stack structure is found to be more suitable for quantum dot VCSELs.