Vertical-cavity　surface-emitting　lasers　(VCSELs)　with　single-mode,　single-polarization　emission　at　a　wavelength　of　894.6　nm　was　demonstrated　for　miniaturized　atomic　clocks.　Utilizing　the　direct-etched　surface　grating　on　the　surface　of　VCSELs,　the　state　of　polarization　of　VCSELs　was　controlled　and　pinned　over　the　whole　current　range.　The　Modal　properties　of　VCSELs　with　grating　structures　was　studied　using　a　finite　difference　time　domain　(FDTD)　method.　We　investigate　modal　loss　behavior　with　respect　to　the　variation　of　grating　structural　parameters　for　the　optimization　of　VCSELs　polarization　characteristics.