Ultra low reflectivity black silicon surfaces and devices enable unique optical applications (Conference Presentation)

Optical devices with features exhibiting ultra low reflectivity on the order of 1e-7 specular reflectance and 0.1% hemispherical TIR in the visible spectrum enable unique applications in astronomical research and instruments such as coronagraphs and spectrometers. Nanofabrication technologies have been developed to produce such devices with various shapes and feature dimensions to meet these requirements. Infrared reflection is also suppressed significantly with chosen wafers and processes. Very low levels of specular and scattered light are achievable over a very broad spectral band. We present some of the approaches, challenges and achieved results in producing and characterizing such surfaces and devices currently employed in laboratory testbeds and instruments. The level of blackness achievable in relation to basic material properties such as conductivity and process variables are discussed in detail.