A sensor for sensing biometric information includes a light emitting unit that emits a first light ray, a light receiving unit that receives a second light ray, where the second light ray includes a portion of the first light ray reflected by a body of a user, and an optical layer placed over the light emitting unit and the light receiving unit. The optical layer has a first surface facing the light emitting unit and the light receiving unit and a second surface opposite the first surface. The optical layer further includes an asymmetrical protrusion structure formed on the first surface or the second surface and including a plurality of asymmetrical protrusion units. The optical layer may further include a symmetrical protrusion structure formed on the first surface or the second surface opposite the asymmetrical protrusion structure and including a plurality of symmetrical protrusion units.