Beam splitter and preparation method and application thereof

The invention belongs to the technical field of optical devices, and particularly relates to a beam splitter and a preparation method and application thereof. The invention provides a beam splitter. The beam splitter comprises a bottoming layer and a plurality of beam splitting film units which are arranged in a stacked mode. The base layer comprises an aluminum layer or a Si3N4 layer; each beam splitting film unit comprises a molybdenum layer and a silicon layer which are stacked; the plurality of beam splitting film units are of a non-periodic multi-layer film structure; the thickness of each beam splitting membrane unit is 1.8 to 5.5 nm; the repetition period number of the beam splitting membrane unit is 20 to 30; and the molybdenum layer of the beam splitting film unit is in contact with the base layer. The obtained beam splitter keeps high reflectivity and transmissivity within the range of 12.5 nm to 15 nm, the reflection efficiency of incident light can be 20% or above under the condition that the inci