Disperse red 1 (DR1) molecules have been successfully incorporated into the one-dimensional channels of AlPO -5 single crystals by means of vapor-phase diffusion. Polarizing microscope and SHG results indicate that the DR1 molecules are well aligned in a preferred direction along the crystal channels. The p-polarization (parallel to the c-axis of AlPO -5 crystal) SH intensity (I ), and s-polarization (perpendicular to the c-axis of AlPO -5 crystal) SH intensity I ) of DR1-loaded AlPO -5 single crystals can be well fitted as a function of input polarization angle (α): I = 0.69 cos α + 0.37 sin α - 0.17, I = 0.69 cos α sin α + 0.06, respectively. This polarization angle dependence can be well explained by three different SHG processes of I (0°), I (90°), and I (45°), originated from different combinations of two polarized photons. © 2006 American Chemical Society.