| CPC H10F 39/8067 (2025.01) [G02B 5/204 (2013.01); G02B 6/10 (2013.01); H10F 39/18 (2025.01); H10F 39/8053 (2025.01)] | 14 Claims |

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1. An optical element (200) comprising:
a layer (211) for filtering radiation by attenuating incident radiation with a frequency that is below a cutoff frequency; and
a transparent element (212),
wherein the layer (211) comprises at least one aperture (213) passing through the layer (211) to the transparent element (212) for propagating radiation therethrough,
wherein the at least one aperture (213) is perpendicular to the plane surface of the layer (211), wherein the at least one aperture (213) has a constant cross section along the axis of the at least one aperture (213) and the cross section is symmetric,
wherein the cross sectional size of the at least one aperture (213) is configured to provide the cutoff frequency so that radiation with a frequency below the cutoff frequency is attenuated inside the at least one aperture (213) and radiation with a frequency above the cutoff frequency propagates through the at least one aperture (213),
wherein incident radiation that does not pass through the at least one aperture (213) is blocked from passing through the layer (211), and
wherein an intensity of radiation that has a frequency below the cutoff frequency and that reaches the transparent element (212) is controlled by the thickness of the layer (211).
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