Here　the　authors　harness　the　on-chip　integration　of　Jones　matrix　metasurfaces　to　demonstrate　an　ultra-compact　approach　to　access　and　manipulate　the　optical　spin　states　of　vertical　cavity　surface-emitting　lasers　(VCSELs)　with　previously　unattainable　phase　controllability.　Polarization　response　of　artificially　structured　nano-antennas　can　be　exploited　to　design　innovative　optical　components,　also　dubbed　＂vectorial　metasurfaces＂,　for　the　modulation　of　phase,　amplitude,　and　polarization　with　subwavelength　spatial　resolution.　Recent　efforts　in　conceiving　Jones　matrix　formalism　led　to　the　advancement　of　vectorial　metasurfaces　to　independently　manipulate　any　arbitrary　phase　function　of　orthogonal　polarization　states.　Here,　we　are　taking　advantages　of　this　formalism　to　design　and　experimentally　validate　the　performance　of　CMOS　compatible　Jones　matrix　metasurfaces　monolithically　integrated　with　standard　VCSELs　for　on-chip　spin-decoupling　and　phase　shaping.　Our　approach　enables　accessing　the　optical　spin　states　of　VCSELs　in　an　ultra-compact　way　with　previously　unattainable　phase　controllability.　By　exploiting　spin　states　as　a　new　degree　of　freedom　for　laser　wavefront　engineering,　our　platform　is　capable　of　operating　and　reading-out　the　spin-momentum　of　lasers　associated　with　injected　spin　carriers,　which　would　potentially　play　a　pivotal　role　for　the　development　of　emerging　spin-optoelectronic　devices.