An optical member including a light guide plate including a surface disposed on a plane defined by a first direction and a second direction crossing the first direction, a low refractive index pattern disposed on the surface of the light guide plate and including an opening for exposing the surface of the light guide plate, a wavelength conversion layer disposed on the low refractive index pattern, and a passivation layer disposed on the wavelength conversion layer and covering a side surface of the wavelength conversion layer and a side surface of the low refractive index pattern at least one side portion. The low refractive index pattern has a lower index of refraction than the light guide plate, and a ratio of an area occupied by the low refractive index pattern to an area of the surface of the light guide plate decreases in the first direction.