A light guide portion includes a low refractive index portion and a high refractive index portion. The low refractive index portion has a refractive index equal to or lower than that of an insulating layer. The high refractive index portion has a refractive index higher than that of the low refractive index portion. The low refractive index portion is located above a separating portion, and is sandwiched by the high refractive index portion in a first direction. A width in the first direction of the low refractive index portion at a first position distant from the separating portion in a second direction is narrower than a width in the first direction of the low refractive index portion at a second position closer to the separating portion than the first position in the second direction.