Luxtera'sdesigneliminates the need to useexpensivegroup iii-vcompounds, such asgallium arsenide (GaAs) andindium phosphate (InP), in thesemiconductors.
The trick is to tune the crystal, by modifying the details of pattern, so that as much of the emitted energy as possible is at the frequency most efficiently captured by indiumgalliumarsenide.
The other, which faces a specialised type of solar cell made of a material called indiumgalliumarsenide, is sculpted into a structure called a photonic crystal that causes it to emit infra-red radiation selectively at the frequency best absorbed by the cell.