Characterization of excitation beam on second-harmonic generation in fibrillous type I collagen

Following our established theoretical model to deal with the second-harmonic generation (SHG) excited by a linearly polarized focused beam in type I collagen, in this paper, we further quantitatively characterize the differences between SHG emissions in type I collagen excited by collimated and focused beams. The effects of the linear polarization angle (α) and the fibril polarity characterized by the hyperpolarizability ratio ρ on SHG emission has been compared under collimated and focused beam excitation, respectively. In particular, SHG emission components along the i axis \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$\left( {I_{2\omega {,}i} } \right)$\end{document} (i = x,y,z), the induced SHG emission deviation angle γij, and the detected SHG signals (I2ω,ij) in the ij plane by rotating the applied polarizer angle φij have been investigated (i = x, x, y; j = y, z, z). Results show that under our simulation model, SHG emission in the xy plane, such as I2ω,x ,I2ω,y ,γxy and I2ω,xy varying as polarization angle (α) under collimated and focused light, presents no significant difference. The reverse of the fibril polarity has induced great impact on I2ω,x ,γxy and I2ω,xy in both collimated and focused light. I2ω,x and γxy show similarity, but I2ω,xy at α = 30° demonstrates a slight difference in focused light to that in collimated light. Under focused light, the reverse of fibril polarity causes obvious changes of the collected SHG intensity I2ω,xz and I2ω,yz at a special polarization angle α = 60° and γxz, γyz along α

Creation of a needle of longitudinally polarized light in vacuum using binary optics

10.1038/nphoton.2008.127Nature Photonics28501-50