Abstract
Polycrystalline CVD diamond is an excellent material for advanced optical applications, especially in the IR spectral range. However, one drawback of diamond is the significant reflection loss of 29%, caused by its high refraction index n = 2.4. We fabricated subwavelength, “moth-eye” antireflective structured (ARS) surfaces (two-dimensional array of pyramids) by filling with CVD diamond the inverted pyramids etched in a Si substrate, followed by the substrate removal to obtain the patterned diamond replica. An increase in IR transmission up to T = 80% was observed at wavelengths λ > 10 μm for the ARS surfaces compared to T = 71% for flat surfaces even at the non-optimized geometry of the surface relief. A further increase in transmission could be achieved by combining ARS and a single layer AR coating of amorphous carbon.
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