A different approach to construct dispersive mirrors (DMs) for ultrafast applications is proposed based on the high reflectivity and constant phase property of a novel metal in ultrawide spectral band. A 200- nm bandwidth DM, a high dispersive DM, and a complementary DM are designed with mixed metal multilayer dielectric stacks. The results show that the mixed-metal multilayer dielectric DMs (MMDMs) have much less layers and total thickness compared with an all-dielectric DM under the case of comparable performance. Such an approach will save manufacturing time and remarkably improve the stress of the DM.
Thermomechanical damage of nodules in dielectric multilayer coatings that are irradiated by nanosecond laser pulses has been interpreted with respect to mechanical properties and electric-field enhancement.However,the effect of electric-field enhancement in nodular damage,especially the influence of electric-field distributions,has never been directly demonstrated through experimental results,which prevents the achievement of a clear understanding of the damage process of nodular defects.Here,a systematic and comparative study was designed to reveal how electric-field distributions affect the damage behavior of nodules.To obtain reliable results,two series of artificial nodules with different geometries and film absorption characteristics were prepared from monodisperse silica microspheres.After establishing simplified geometrical models of the nodules,the electric-field enhancement was simulated using a three-dimensional finite-difference time-domain code.Then,the damage morphologies of the artificial nodules were directly compared with the simulated electric-field intensity profiles.For both series of nodules,the damage morphologies reproduced our simulated electric-field intensity distributions very well.These results indicated that the electric-field distribution was actually a bridge that connected the nodular mechanical properties to the final thermomechanical damage.Understanding of the damage mechanism of nodules was deepened by obtaining data on the influence of electric-field distributions on the damage behavior of nodules.
Xinbin ChengJinlong ZhangTao DingZeyong WeiHongqiang LiZhanshan Wang
