Implantable medical device comprising an optical unit

An implantable medical device (1) comprising:

• (a) a housing (2) defining an inner volume separated from an outer environment, and enclosing an electronic circuit and source of power, and
• (b) an optical unit (3) sealingly coupled to the housing, said optical unit comprising:
• a monolithic block unit (4) made of a transparent ceramic material which is transparent to wavelengths comprised between 300 and 2200 nm, and comprising:
• a thin window (4w) defined by an inner surface facing the inner volume of the housing and an outer surface facing the outer environment,
• an outer mating structure (4om) located on the side of the outer surface of the thin window, for coupling an outer fibre optic (9) in alignment with a corresponding reference point (4r) of the inner or outer surface of the thin window, and
• an inner mating structure (4im) located on the side of the inner surface of the thin window, for permanently coupling a light unit (5), and
• a light unit (5) comprising a light element including one or more of an inner light source (5L), and/or photodetector (5d), and/or inner fibre optic, said light unit being rigidly mounted in the inner mating structure (4im) of the monolithic block unit, such that one of the inner light source (5L), and/or photodetector (5d), and/or inner fibre optic is in alignment with said corresponding reference point (4r) of the inner or outer surface of the thin window.