The reflection Talbot effect under the illumination of Gaussian spherical wave and plane wave is observed on 1D and 2D photonic crystal of silicon prepared by nanosecond laser. It is found that the distance between two adjacent Talbot images increases lineally with increasing of image distance as well as amplification of Talbot images under the illumination of Gaussian spherical wave. The result of theory is coincident with that of experiment, which shows that selecting suitable wavefront shape of input field can enlarge the amplification rate and improve the resolution of Talbot imaging. The reflection Talbot effect will have a lot of good application in microscopy of micro-fabrication on silicon, such as detecting period structures of plasma on line of PLD fabricating.
The curved surface(CS) effect on nanosilicon plays a main role in the activation for emission and photonic manipulation.The CS effect breaks the symmetrical shape of nanosilicon on which some bonds can produce localized electron states in the band gap.The investigation in calculation and experiment demonstrates that the different curvatures can form the characteristic electron states for some special bonding on the nanosilicon surface,which are related to a series of peaks in photoluminecience(PL),such as L N,L NO,L O1,and L O2lines in PL spectra due to Si–N,Si–NO,Si=O,and Si–O–Si bonds on curved surface,respectively.Si–Yb bond on curved surface of Si nanostructures can provide the localized states in the band gap deeply and manipulate the emission wavelength into the window of optical communication by the CS effect,which is marked as the L Yb line of electroluminescence(EL) emission.
A curviform surface breaks the symmetrical shape of silicon quantum dots on which some bonds can produce localized electronic states in the bandgap.The calculation results show that the bonding energy and electronic states of silicon quantum dots are different on various curved surfaces,for example,a Si-O-Si bridge bond on curved surface provides localized levels in bandgap and its bonding energy is shallower than that on the facet.The red-shifting ofthe photoluminescence spectrum on smaller silicon quantum dots can be explained by the curved surface effect.Experiments demonstrate that silicon quantum dots are activated for emission due to the localized levels provided by the curved surface effect.
