Silicon crystal planes that can be potentially used as optical mirrors for deflecting light beams from/to optical fibres aligned in grooves were investigated. Aligning grooves and passive mirror-like planes were formed by wet micromachining in KOH and TMAH etchants with addition of additives such as IPA and Triton surfactant. On (100) silicon, {111}, {110}, {311} mirror planes were realized, while on (110) silicon, {010} and {111} mirror planes were demonstrated for the chosen mask orientation. Characterization of passive mirrors with 632nm incident light was performed by measuring angles and specific shape patterns of reflected light beams and by determination of light scattering due to mirror microroughness. Results show that {111} planes exhibit better surface quality compared to {110} mirrors and lowest scattering, however the reflected angle is 54,74° on (100) silicon. On (110) silicon the 45° reflection angle with {010} crystal planes is obtained by proper mask alignment with very small scattering angle below 3°. For reflecting the beam with 1,33 μm wavelength, sputtered layer of aluminum is used as reflecting coating on silicon mirrors, increasing the reflectivity by 24%.
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