Optical properties are studied for Se species accommodated in channels of an AlPO-5 single crystal. Polarized Raman spectra show that the Se species is of helical chain structure with D symmetry. The optical phonon modes of the Se chains are shifted towards higher frequencies from that of the trigonal Se crystal, because of the loss of inter-chain interactions in Se/AlPO-5. High anisotropic absorption spectra have been observed for the Se chains. The lowest excitation energies are shifted towards high energy about 0.6 eV from the band edge transitions of the trigonal Se crystal. The blue shift is attributed to the quantum confinement of carriers in a Se chain with diameter 7.3 Å. © 1998 Academic Press Limited.