Implantable Optical Sensor With Hermetically Sealed Cover Cap

An implantable optical sensor comprises a photonic integrated circuit comprising a substrate 2 and an optical microstructure 3 integrated with the substrate 2. The optical microstructure is positioned to form an exposed optical interaction area 4 on a part of a surface 5 of the substrate 2. A cover cap 6 is sealed onto a part of the substrate 2 adjacent to the optical interaction area 4 and by wafer-to-wafer bonding technology or another wafer-level hermetic packaging technique. At least one active component 8 is positioned in a sealed cavity 9 which is formed between the surface 5 and the cover cap 6. The substrate 2 comprises at least one optical feedthrough 10, which is an embedded waveguide extending from the sealed cavity 9 to the optical interaction area 4.