A dichroic (or multichroic) beam splitter operating in the high energy laser HEL environment is called a shared aperture component and is becoming an increasingly desirable component in the design of HEL systems. At present, there are four basic types: Buried Short Period (BSP) grating, Buried Long Period (BLP) grating, Dichroic Beam Splitter (DBS) and Compound Interlaced (CI) grating. The BLP grating and CI grating are new types of grating which have recently been proposed and are currently under development. This paper describes the four basic types and their characteristics. Their design and fabrication issues and present technology status are also discussed.