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When Geoff Met Shuji

Issue 85 June / July 2015

Technology expert Dr Geoff Archenhold was suitably impressed with Soraa’s philosophy when he attended its recent event in London. He also got a sneak preview of new products and had the opportunity to meet the notable Dr Shuji Nakamura.

Where Quality of Light, Technology and Nobel Prizes converge

There are three areas where LED lighting still has to excel although one would be forgiven for thinking the only game in town is ‘smart lighting’ these days. In order for LED lighting to be the only mainstream lighting technology that will never be supplanted by another technology in the history of man it has to improve on:

Maximum Wall Plug Efficiency (WPE)

Quality of Light

Seamless Intelligent Building Integration (SIBI)

It is clear there will be several leading lighting players that will show the rest of the industry the way to deliver on each of these three goals over the longer term. One such leader will be Soraa which has harnessed some of the greatest minds in the LED components industry including Co-Founders Dr Shuji Nakamura, Winner of 2014 Nobel Prize in Physics, Dr Steve Denbaars and Dr James Speck.

I recently had the honour of meeting Dr Shuji Nakamura at the recent Soraa event in London to discuss their technology leadership, lighting industry vision and a sneak preview of the new products and I was suitably impressed about their whole philosophy moving forward as you will see.

Most efficient LEDs yet devised

It is clear that a unique differentiator of Soraa from any number of LED lamp manufacturers is its focus on industry leading LED die and emitter technologies. It is well known that Dr Shuji Nakamura along with other contributors at Nichia created an efficient blue LED from InGaN and combined it with an efficient YaG phosphor to create a white LED light nearly two decades ago. That innovation has clearly not stopped and today the team at Soraa has created an innovative triangular shaped, bulk GaN flip-chip device combined with a three-part phosphor to create a full spectrum LED emitter that provides a highly efficient and superb quality lighting experience. The novel chip design (fig.1) has a maximum wall plug efficiency of 84% at 85ºC (this means 85% of the electrical energy is converted into light) which is significantly higher than the majority of LED’s on the market place and allows Soraa to significantly improve the thermal management of packing LEDs into small areas and hence why Soraa focused on lamps because of the severe thermal challenge of creating retrofit LED lamps.

Dr Nakamura was keen to point out they have achieved their outstanding performance by combining a GaN active layer on a GaN substrate and commonly known as GaN-on-GaN. Using this topology it is possible to reduce the dislocation areas with the active layers which effectively improve the efficiency of the LED and there is less thermal stain and improved thermal matching during the production of the LED die.

There are associated known issues with using GaN substrates and two of them have been the availability of large GaN wafer sizes with associated wafer costs and supply chain diversity however Dr Nakamura has recently pointed out that Soraa has started to move to four-inch wafers from the two-inch versions, which enable a significant increase in production volume capacity and a reduction of production costs. It is anticipated just as the growth in wafer size for SiC or Sapphire occurred the same should occur for GaN based substrates and thus economies of scale should be achievable over the next few years.


Highest Quality of Light Solved?

The key to providing a quality of light experience is built upon two main factors:

1. The light spectrum quality emitted from the light source

2. The ability to harness and shape the emitted light

Soraa has achieved the first metric by using a Violet LED that emits its peak wavelength at around 415nm (fig.2) and combining this with an efficient three-part phosphor to create an excellent full spectrum with no gaps or severe spikes normally associated with typical lighting sources. To be fair, Soraa wasn’t the first to develop such LED lighting as some of you will remember that GE did it first. However, Soraa has managed to push the efficacy much higher due to its own LED die engineering triumphs. The key to quality of light spectrum engineering is a continuous spectrum that has great red content and that is where the three-part phosphor really excels with very high R9.

Interestingly, Soraa may have just cracked the second important metric by combining single die technology with good optical engineering through the use of novel light diffuser optics to allow a light fixture to create exciting beam patterns efficiently. This was capably demonstrated at the event with some new magnetic clip-on optics that allowed an LED lamp hanging from a ceiling and pointing down to create a near square beam pattern at virtually 45º with no light spillage below the lamp. It was then possible to rotate the magnetic optic and the beam pattern would rotate so as to easily allow the beam to be placed where you would want without having to move the lamp or fixture holding. The ability to use a single-die to create such a high brightness output also enables the lamp to reduce shadowing (usually found in multi-die COB devices) and it was claimed this was a key for the adoption of Soraa lighting in casinos as it allows improved video camera imaging that can improve detection of cheating.

I could definitely see the light shaping and single-die technology combination used in museum and retail applications and it’s great to see that some of Jeff Parkers (CEO of Soraa) knowledge of optical engineering has been put to good use.

It definitely feels like Soraa is teaching the LED industry how to pull together a great quality of light package in an efficient manner, and where leaders go the rest are sure to follow, which is great news for all.


Intelligent Building Integration?

Everyone wants a smart lamp, right? So Soraa demonstrated a prototype of one of its retro fit lamps, which included a Bluetooth interface to enable control from a mobile device and to allow the lamp to be switched off remotely and dimmed up and down.

It became evident that this is definitely one area where Soraa does not have a technology leadership and needs to seriously decide strategically how it tackles ‘smart’ lighting moving forward. The demonstration system had a very basic GUI on the mobile device which being a prototype I could significantly understand. However the overriding issue that ruled its credibility out was the latency of control response. I estimated that although I was less than one metre away from the lamp it took between 500mS and 700mS for the light to respond to a command, which is not only frustrating but not usable when working with a large number of fixtures.

There is no doubt that lighting should add a degree of control especially as there is very little cost added to achieve this. However we are in the Wild Wild West of ‘smart’ lighting today and my advice to the Soraa team is to hire some experts in this field so they can excel as they do with the rest of their engineering staff.


So what is the future of Lighting?

Having spent some one-to-one time with Dr Nakamura, we brainstormed what the next steps of the lighting industry could be and the main conclusions were:

Improvement of LED WPE could possibly reach 90% but the challenges to achieve this are extremely difficult as most of the easy-optimisation has been achieved over the last 20 years. At some point the diminishing returns on investment would mean the leap from 84% to 90% WPE will be tough and possibley unattainable for most other SiC and Sapphire substrate manufacturers.

Gan-on-Gan technology is the second generation of LED lighting as it enables violet lighting, high efficiency full-spectrum light output that has great thermal management properties.

Laser-based lighting is definitely an area to watch according to Dr Nakamura and Soraa has created a second company called Soraa laser diodes, which works on creating a high efficiency blue lasers for lighting applications. Dr Nakamura cited the use of laser lighting in prototype automobile headlamps and laser projectors as the way to go and that Soraa sees laser lighting proliferate across the general lighting industry within the next five to ten years. Interestingly, Panasonic demonstrated four years ago its laser lighting prototype at Light + Build but the challenge will be to increase the blue laser diode efficiency and reduce the costs which Soraa believes it is well placed to achieved.

LI-FI is an interesting technology as it allows LED manufacturers a new potential business opportunity outside of light and allows them to offer data streaming capabilities from LED lamps.

All in all it was a great event and a pleasure to speak with Dr Nakamura. I wish the team at Soraa well and I look forward to seeing their laser lighting products soon!

Geoff Archenhold is an active investor in LED driver and fixture manufacturers and a lighting energy consultant. 


The views expressed in this article are those of the author and do not necessarily represent the views of mondo*arc.


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