Photodiode (100; 200; 500; 600; 700; 800) of SPAD type, having a layer made of semiconductor material (110; 210) including an N doped zone (111; 511; 611) and a P doped zone (112; 512; 612), separated by PN junction with an avalanche zone (113; 213; 513; 813A; 813B) extending in and around the PN junction, said photodiode further comprising - a first so-called low index layer (130; 230; 530; 630; 730); and - a periodic structure (120; 220; 520; 620; 720) having a plurality of elementary patterns, that is to say a plurality of pads (121; 521) regularly spaced apart from each other and arranged according a pitch; wherein: the pitch P of the periodic structure (120; 220; 520; 620; 720) is greater than the ratio λ n eff, and less than the ratio λ n ginf, with: - λ the wavelength that the photodiode is intended to detect, - n eff the actual index of the waveguide formed in the photodiode, equal as a first approximation to the refractive index of the layer (110; 210) made of semiconductor material, and - n ginƒ, the refractive index of the first low index layer (130; 230; 530; 630; 730) the first low index layer (130; 230; 530; 630; 730) having a refractive index less than that of the semiconductor material layer and than that of the periodic structure, and the semiconductor material layer (110; 210) being intercalated between the first low index layer and the periodic structure, - the periodic structure (120; 220; 520; 620; 720) being arranged on the PN junction - the semiconductor material layer (110; 210) being intercalated between the first low index layer (130; 230; 530; 630; 730) and the periodic structure (120; 220; 520; 620; 720) that is directly lying on the the semiconductor material layer (110; 210), - the periodic structure (120; 220; 520; 620; 720) being made of semiconductor and in a same semi-conductor bloc that the semiconductor material layer (110; 210) or being formed in a polycrystalline layer formed on the semiconductor material layer. - a first so-called low index layer (130; 230; 530; 630; 730); and - a periodic structure (120; 220; 520; 620; 720) having a plurality of elementary patterns, that is to say a plurality of pads (121; 521) regularly spaced apart from each other and arranged according a pitch; the pitch P of the periodic structure (120; 220; 520; 620; 720) is greater than the ratio λ n eff, and less than the ratio λ n ginf, with: - λ the wavelength that the photodiode is intended to detect, - n eff the actual index of the waveguide formed in the photodiode, equal as a first approximation to the refractive index of the layer (110; 210) made of semiconductor material, and - n ginƒ, the refractive index of the first low index layer (130; 230; 530; 630; 730) - λ the wavelength that the photodiode is intended to detect, - n eff the actual index of the waveguide formed in the photodiode, equal as a first approximation to the refractive index of the layer (110; 210) made of semiconductor material, and - n ginƒ, the refractive index of the first low index layer (130; 230; 530; 630; 730) the first low index layer (130; 230; 530; 630; 730) having a refractive index less than that of the semiconductor material layer and than that of the periodic structure, and the semiconductor material layer (110; 210) being intercalated between the first low index layer and the periodic structure, - the periodic structure (120; 220; 520; 620; 720) being arranged on the PN junction - the semiconductor material layer (110; 210) being intercalated between the first low index layer (130; 230; 530; 630; 730) and the periodic structure (120; 220; 520; 620; 720) that is directly lying on the the semiconductor material layer (110; 210), - the periodic structure (120; 220; 520; 620; 720) being made of semiconductor and in a same semi-conductor bloc that the semiconductor material layer (110; 210) or being formed in a polycrystalline layer formed on the semiconductor material layer. - the periodic structure (120; 220; 520; 620; 720) being arranged on the PN junction - the semiconductor material layer (110; 210) being intercalated between the first low index layer (130; 230; 530; 630; 730) and the periodic structure (120; 220; 520; 620; 720) that is directly lying on the the semiconductor material layer (110; 210), - the periodic structure (120; 220; 520; 620; 720) being made of semiconductor and in a same semi-conductor bloc that the semiconductor material layer (110; 210) or being formed in a polycrystalline layer formed on the semiconductor material layer.