Noisy signals with 2-layer PCB - What's wrong with my design?
May I present the LT1761 regulator circuit complete with recommended capacitors on inputs and outputs: -



On your PCB design I see only a 10 nF capacitor. I also don't see a device footprint that matches the footprints shown in the data sheet but I could be mistaken about this. Looking at the circuit you have linked....



Try and learn to use vias and be clever about avoiding routing on the ground layer. Think about this for instance: -



The ground flood will be much better just for a bit of thinking about the problem. Make your supply lines (orange) much thicker too AND think about how they route - look how yours pointlessly splits around the 10 nF capacitor!