Micro　light　sources　are　crucial　tools　for　studying　the　interactions　between　light　and　matter　at　the　micro/nanoscale,　encompassing　diverse　applications　across　multiple　disciplines.　Despite　numerous　studies　on　reducing　the　size　of　micro　light　sources　and　enhancing　optical　resolution,　the　efficient　and　simple　fabrication　of　ultra-high-resolution　micro　light　sources　remains　challenging　due　to　its　reliance　on　precise　micro-nano processing　technology　and　advanced　processing　equipment.　In　this　study,　a　simple　approach　for　the　efficient　fabrication　of　submicron　light　sources　is　proposed,　namely　shadow-assisted　sidewall　emission　(SASE)　technology.　The　SASE　utilizes　the　widely　adopted　UV　photolithography　process,　employing　metal　shadow　modulation　to　precisely　control　the　emission　of　light　from　polymer　sidewalls,　thereby　obtaining　photoluminescent　light　sources　with　submicron　line　widths.　The　SASE　eliminates　the　need　for　complex　and　cumbersome　manufacturing　procedures.　The　effects　of　process　parameters,　including　exposure　dose,　development　time,　and　metal　film　thickness,　on　the　linewidth　of　sources　are　investigated　on　detail.　It　is　successfully　demonstrated　red,　green,　and　blue　submicron　light　sources.　Finally,　their　potential　application　in　the　field　of　optical　anti-counterfeiting　is　also　demonstrated.　We　believe　that　the　SASE　proposed　in　this　work　provides　a　novel　approach　for　the　preparation　and　application　of　micro　light　sources.　(Figure　presented.)　©　The　Author(s)　2025.