Due　to　the　degenerate　spectral　response　of　the　human　vision　system,　different　sets　of　primary　colors　can　cover　the　same　color　space.　Thus,　we　propose　to　generate　multiple　focal　planes　in　head-mounted　displays　to　mitigate　the　vergence　accommodation　conflict　(VAC)　through　wavelength　multiplexing,　making　use　of　another　dimension　of　light　as　the　information　channel　for　cascading　2D　images　to　3D　scenes.　Conventional　approaches　based　on　space-　or　time-multiplexing　can　provide　multifocal　functionality　but　with　a　significant　sacrifice　in　resolution　or　frame　rate.　As　a　novel　alternative,　polarization　multiplexed　methods　can　avoid　these　drawbacks,　but　they　can　only　achieve　two　focal　depths　since　there　are　only　two　orthogonal　polarization　states.　The　wavelength　multiplexing　proposed　here　is　intrinsically　free　from　all　the　limitations　mentioned　above.　Firstly,　as　a　proof　of　concept,　we　built　a　dual-focal　near-eye　display　using　off-the-shelf　optical　components.　The　prototype　is　designed　based　on　a　birdbath　architecture　with　an　extra　spectral　notch　filter　as　the　wavelength-sensitive　depth　separation　element.　The　optical　powers　for　the　two　wavelength　sets　are　determined　by　the　distance　between　the　reflector　and　notch　filter.　Our　benchtop　demo　can　generate　two　focal　depths　simultaneously,　which　are　located　at　1　m　and　2　m　away　from　the　optical　combiner.　Moreover,　another　compact　optical　design　of　a　wavelength-multiplexed　dual-focus　light　engine　for　lightguide　type　AR　displays　is　also　presented.　Also,　we　analyze　the　implementation　of　full-color　operation　and　demonstrate　an　angle-insensitive　multi-notch　filter　design　based　on　optical　multi-layer　coatings.　Finally,　we　discuss　practical　limitations　and　potential　improvement　of　the　proposed　wavelength　multiplexing　method　for　overcoming　the　VAC　issue.