• Submicron light sources are realized using only standard UV photolithography, enabling arbitrary patterns without complex nanofabrication.
• A novel shadow-assisted sidewall emission (SASE) technique precisely controls polymer sidewall emission via metal shadow modulation.
• Red, green, and blue submicron light sources are successfully demonstrated, with linewidth tunable by exposure dose, development time, and metal thickness.
• The SASE-based light sources show strong scalability and are proven applicable in optical anti-counterfeiting, offering a cost-effective route for high-resolution micro-optics.