LIGHT ACQUISITION SHEET AND ROD, AND LIGHT RECEIVING DEVICE AND LIGHT EMITTING DEVICE EACH USING THE LIGHT ACQUISITION SHEET OR ROD

A light-trapping sheet of the present invention includes: a light-transmitting sheet 2 having first and second principal surfaces; and a plurality of light-coupling structures 3 arranged in an inner portion of the light-transmitting sheet at a first distance or more and a second distance or more from the first and second principal surfaces, respectively, wherein: each of the plurality of light-coupling structures 3 includes a first light-transmitting layer, a second light-transmitting layer, and a third light-transmitting layer arranged therebetween; a refractive index of the first and second light-transmitting layers is smaller than a refractive index of the light-transmitting sheet 2; a refractive index of the third light-transmitting layer is larger than the refractive index of the first and second light-transmitting layers; and the third light-transmitting layer has a diffraction grating parallel to the first and second principal surfaces of the light-transmitting sheet.