UK-based Plessey has developed a patented technology for chip-scale optics (CSO) based on its gallium nitride on silicon MaGIC (Manufactured on GaN-on-Si I/C) LEDs.
Chip-scale optics permits the design of light emission angles down to 10° direct from the LED. Having the primary optics on-chip eliminates the cost of primary optics typically found in packaged LEDs and chip-on-board modules. Furthermore, it significantly lowers the cost and provides for far greater design freedom for secondary optics within a luminaire, says the firm. The first applications include retail spot lighting, hospitality lighting, high and low bays, street lighting and stadium lighting. It is estimated that Plessey's chip-scale optics can halve the cost of these lighting applications.
"The CSO technology was originally designed as an on-chip phosphor dam," says Plessey's chief technology officer Dr Keith Strickland. "We realised that the original growth silicon, normally sacrificed during LED production, could be shaped and used to form mechanically robust, MEMS-type features on the emitting surface of a vertical LED. The degree of collimation is controlled in part by the mechanical dimensions of these on-chip structures, and we have demonstrated emission angles as low as 10°. The IC industry has used silicon for over 60 years and can be readily fashioned into many shapes and patterns. We have created silicon MEMS features in a variety of other applications and can manage to incorporate a complex primary optical design on the chip," he adds.
"High-end lighting designers do not count lumens per Watt as the primary figure of merit for LEDs," notes Plessey's principal optical designer Dr Samir Mezouari. "A lighting designer aims to illuminate a particular surface area. Chip-scale optics can significantly simplify luminaire designs by forming symmetrically collimated beams with narrow angles or asymmetric beams to form elongated far-field light profiles," he adds. "Schemes to collimate monochromatic light at the LED level have been developed before, but no-one has previously collimated white light at the LED level."
Plessey will be exhibiting an LED demonstrator of the chip-scale optics at LuxLive (the UK largest lighting show) at London's ExCeL arena (18-19 November). Samples will be available in first-quarter 2016.
