A backlight unit includes a light guide layer including a plurality of extraction features disposed along a rear face of the light guide layer, a first cladding layer adhesively secured to the rear face of the light guide layer, a plurality of turning structures disposed along the first cladding layer, and a second cladding layer adhesively secured to a front face of the light guide layer. The first cladding layer has a first refractive index lower than a guide refractive index of the light guide layer. The second cladding layer has a second refractive index lower than or equal to the first refractive index.