Method for producing a reflective optical element, reflective optical element, and use of a reflective optical element

A method, comprising:

• filling a cavity in a substrate with a second material, the substrate comprising a first material;
• using galvanic and/or chemical deposition of a third material to apply an overcoating to a first surface of the substrate in a region of the cavity;
• removing the second material from the cavity;
• and
• before or after removing the second material from the cavity, applying a reflective layer to the overcoating,
• wherein the method forms an optical element, which comprises:
• the substrate;
• the overcoating on the first surface of the substrate;
• the cavity;
• and
• the reflective layer,
• wherein:
• the reflective layer comprises an optically effective surface;
• the cavity is near the first surface of the substrate;
• the overcoating extends over the cavity;
• the cavity is free of material of the overcoating;
• and
• the reflective layer is on a surface of the overcoating that faces away from the substrate.