Wavelength tunable optical filter, optical module, and electronic apparatus

A wavelength tunable optical filter comprising:

• a substrate;
• a first encased reflective film provided on the substrate, the first encased reflective film including a first reflective film and a first protective film entirely encasing the first reflective film;
• a second encased reflective film, the second encased reflective film including a second reflective film and a second protective film entirely encasing the second reflective film, the second reflective film facing the first reflective film, and
• a supporting portion provided over the substrate, the supporting portion supporting the second encased reflective film at a predetermined distance from the first encased reflective film, the supporting portion having an inner circumferential wall defining a cylindrical interior space between the first encased reflective film and the second encased reflective film;
• wherein the second encased reflective film has a plurality of through-holes collectively forming a circular array by being disposed along a circumference of a circle in a plan view of the second encased reflective film, a center of the circular array and a center of the cylindrical interior space are concentric in the plan view, and
• wherein for every through-hole of the circular array of the second encased reflective film, a distance from the corresponding through-hole to the inner circumferential wall of the supporting portion along a corresponding line segment passing through both (i) the center of the circular array and (ii) the corresponding through-hole is equal to or greater than a diameter of the circular array.