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Desirable light absorption with optical bandpass filters

A recent innovation at the University of Utah sheds light – quite literally – on the benefits of optical bandpass filters as a way of absorbing light.

Engineers at the university have developed an etched silicon wafer with nanoscale pillars and tiny holes, with their completed prototype measuring just 20 microns in height and width.

The wafer acts as a polariser – not only allowing light polarised in one direction to pass through it, but also reconfiguring a portion of the remaining light to allow it through as well.

As a result, around three quarters of the total light is let though, rather than the maximum of 50% achievable with conventional polarising filters.

The hope is that, in the future, polarised displays like LCDs will be able to be much brighter, without consuming so much battery power.

But it’s worth remembering that in some instances, absorbing light is exactly what you want – and optical bandpass filters do this not by polarising the light, but by selecting specific wavelengths to allow through.

These absorption filters can make their own valuable contribution to reducing reflected light in an entirely different way to polarising filters, with the benefit that the wavelengths transmitted through the filter can be much closer to their original brightness.