ScienceDaily (July 2, 2009) — It appears to be a paradox: ultra-thin material that absorbs all the incident light. Nonetheless, it does exist.

How much light is reflected and how much is absorbed depends on two factors: the angle at which the light falls onto the material, and the polarisation (the direction of oscillation) of the light. (Credit: Image courtesy of Leiden University)

Two researchers, Eduard Driessen, MSc, and Dr Michiel de Dood, have demonstrated that at a thickness of 4.5 nanometer niobiumnitride (NbN) is ultra-absorbent. They have recorded a light absorption of almost 100%, while the best light absorption to date was 50%. This research brings the ideal light detector a step closer.

A cell made of this material can already collect light and convert it into an electrical signal. The high number of downloads indicates that this research is very special.

Angles and polarisation

Materials that could potentially absorb a lot of light have the problem that they reflect the incident light; they are generally very good mirrors. But how much light is reflected and how much is absorbed depends on two factors: the angle at which the light falls onto the material, and the polarisation (the direction of oscillation) of the light. Light has two kinds of polarisation: s and p polarisation.

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