A method of manufacturing a detector capable of detecting a wavelength range [λ8; λ14] centered on a wavelength λ10, including: forming said device on a substrate by depositing a sacrificial layer totally embedding said device; forming, on the sacrificial layer, a cap including first, second, and third optical structures transparent in said range [Δ8; λ14], the second and third optical structures having equivalent refraction indexes at wavelength λ10 respectively greater than or equal to 3.4 and smaller than or equal to 2.3; forming a vent of access to the sacrificial layer through a portion of the cap, and then applying, through the vent, an etching to totally remove the sacrificial layer.