Micropolarizer fabricated from CaCO₃by anisotropic wet etching

A micropolarizer is fabricated on a birefringent crystal, calcite, by anisotropic wet etching. This device consists of a v-groove grating on calcite, covered by an index-matching material. The grating is fabricated by acid wet etching. When its acid concentration and stirring speed are altered, the etching mechanism can be controlled within the surface-reaction regime. This results in anisotropic etching, which produces a v-groove grating on a calcite surface. This v-groove grating can be fabricated to have a period as small as 2 μm. To the best of our knowledge, this type of v-groove calcite grating is reported for the first time. Although the transmission efficiency of this device is wavelength dependent, a broadband micropolarizer can be made by gluing together two devices with periods of 12 and 16 μm.