Abstract: An optical element of the present invention comprises a fluorite substrate 1, and a lanthanum fluoride film 2 formed directly on the substrate 1. The substrate 1, on which the lanthanum fluoride film 2 is formed, has a plane which is a (111) plane or a plane inclined by an angle within ±30 degrees, preferably within 15 degrees from the (111) plane. Therefore, the lanthanum fluoride film undergoes the crystal growth subjected to the C-axis orientation on the optical substrate. Since the lanthanum fluoride film is dense and has a small surface area, it scarcely involves the oxidation and hydroxylation areas as well as the structural defect. Therefore, it is possible to reduce the optical loss of the optical element in the vacuum ultraviolet region.

Abstract: An optical information recording medium, having information recorded along a track going from the inner circumference to the outer circumference, a lead-in region storing information relating to the recorded data contents of a program region, the program region where data is recorded, and a lead-out region which shows an end of the track, wherein the track pitch of the lead-out region is made narrower than the track pitch of the lead-in region and the program region.