Tech-Talks BREGENZ - Julian Carey, Marketing Manager at SLD Laser

LED professional: Thank you for being here and agreeing to this interview. Can you tell us a little about SLD Laser?

Julian Carey: Yes, of course. SLD Laser is an independent spinout. Shuji Nakamura, our co-founder, who won the Nobel Prize in physics in 2014, and who also founded SORAA, wanted to move on towards laser technology. He saw that there was so much potential for blue laser to contribute in lighting. So as a result, several of the co-founders left SORAA, and founded SLD Laser. Both companies now have their offices in Silicon Valley but they are independent companies that have independent customers. Markets, technology and products – pretty much everything is different at this point. SLD Laser got its start with automotive technology – going into the headlights and became an automotive supplier and the company is going into production this year with those applications.
That gave it a good foundation to go into general lighting, or specialty lighting really: Spots, entertainment, architectural lighting and some fiber optic applications.
The company is headquartered in Santa Barbara close to the University of California, where we have a lot of access to technology. They have a very strong department there, which specializes in high power semiconductors. It's an important location but most people now work for the SLD Laser in the Silicon Valley in Northern California.

LED professional: How many people work for SLD Laser?

Julian Carey: Now we have 120 people worldwide, we're actually growing quite a bit. And that's really to ramp operations as we go into automotive headlight production, which started in October 2018. Before that we shipped quite a few verification units of our laser light SMD product. It is a LED-like square shaped SMD with 500 lumens. That went into production in September. So we are already shipping several thousand units.

LED professional: You said that SLD Laser is making all the automotive headlights, so are you doing the complete process from the solid-state laser with everything that is needed for electronics and the complete assembly?

Julian Carey: That's right.

Flashlights with narrow beam angles are one of the applications that can take full advantage of laser light

LED professional: How is it split? Is the laser one part and the assembly another?

Julian Carey: It's sort of like the business model. In summary – we fabricate laser chips in a two-stage process. The epi fabrication is in Santa Barbara and the wafer fabrication is in Freemont. Once those chips are made – they are like the equivalent of LED die – they're blue lasers. The difference is that the light density is about 100 times that of an LED. Then we make different modules. So right now we have two main product platforms. One is the fiber module for automotive headlights – where the laser module is separated from the phosphor by a fiber optic cable – and that has some advantages thermally and optically.  And then the SMD product combines lasers and phosphor in one SMD package to make it present itself like an LED. So you put it on the PCB and use the same type of optics. 

Business models are a little bit different between the two. We fit into the automotive infrastructure in a very traditional way. We supply our light module to the headlamp sub-system manufacturer. And they, in turn, would supply the complete headlight module that then gets assembled into the vehicle by the car manufacturer. So SMD is more straightforward and traditional, like the LED model, where we engage with lighting-OEMs, who then manufacture lighting equipment.

Extending the reach of a vehicle's high beam was one of the first mass laser lighting applications

LED professional: You just said that this SMD laser is about 500 lumens. But for a car headlight, you need a lot more – so how do you achieve that?

Julian Carey: Specifically about the automotive roadmap: right now we only do the high beam extender function which is about 400 lumens. So that gives you about a one-kilometer range of visibility – usually in combination with the high beam at very high speeds. The complete headlight module still has many LEDs for the low beam, the daytime running light and all of those indicators. The future will have lasers effectively implementing the entire headlight by combining laser chips. But the nice thing about the fiber module architecture is that you can combine multiple lasers into one fiber and then when they hit the phosphor you can have a very high illuminance source. Through the headlight, in its entirety, you'd probably need about 2,000 lumens and probably about five laser chips but you'd still maybe have a single phosphor, so you'd still have one source that you could then manipulate dynamically. There are a lot of ideas about how to combine different pieces of the entire headlight.

LED professional: Is there a technical limitation?

Julian Carey: The only limit is really the thermal limit of the phosphor. But for the phosphors used in automotive lighting, that's quite high. It's easily 200°C. We just make sure that we don't make it so intense that it would damage the phosphor. Nonetheless, we can stay within safe range of the phosphor but still, in the automotive context, have luminance levels that are six, seven or even eight times more dense than LEDs can. This gives you optical control and sharp cutoff and a whole lot of benefits like the ability to use the dynamic reflectors.

Search lights and safety equipment for offroad vehicles is another strength of laser lights

LED professional: So just to understand how the laser and the conversion work: There is a very, very narrow blue beam, and this beam hits the converter. What is the distribution of the white light behind the converter?

Julian Carey: There are a few stages to that. I think some people imagine laser chips as having a perfect beam right out of the facet, but they don't, actually. The light is still diverging. It comes from a very, very tiny spot but it's quickly diverging. In the fiber module case, there are optics that are right close to the laser that collimate the beam and then get it back – refocus – so that it can enter the fiber. The fiber has a distal end that has its own diversions properties. So when it is placed with the phosphor, it has to be placed very carefully so that you have the right density. We basically try to have the light come to the phosphor in a highly uniform way so you don't have any hotspots. But the white light that results is very similar to an LED, just much smaller. It's still a diffuse, Lambertian distribution, it has good color over angle. The systems just get a little more sensitive because positioning accuracy now becomes more important with a very high luminance small source. Both with the SMD and the fiber module, the entire luminous area is only 300 microns in diameter for 500 lumens. It's just incredibly tiny and positional accuracy can sometimes be 100 microns, so you have to make sure that your optics are very, very precise.

LED professional: The luminance area is about ten times smaller than that of an LED.

Julian Carey: That's right. But there are a lot of different kinds of LEDs. We compare with LEDs that are engineered for high luminance. Chip on Board arrays are actually very large sources, but if you look at automotive LEDs or LEDs specifically for very high intensity application, that's where that comparison is valid.

LED professional: The big advantage of the LED laser is the small size.

Julian Carey: Exactly, because then you have design possibilities for very long throw and very small optics and very high efficiency through a collimated type of scenario. That's why all of our applications are basically spots or fiber optic. It's not really an application that is going to go into highly diffused or extended sources.

LED professional: There are many technical differences between the LED and the laser – starting with the manufacturing process of the die, going on to the accuracy of the assembly, and also the driver. One thing you mentioned was the high-power LEDs and the fact that if you even have a little spec of dirt on the lens, it could be critical. How do you avoid something like that?

Julian Carey: We definitely have to make sure that the optics are high temperature capable. If you have plastic objects they could melt if their temperature capability is too low. You're absolutely right – anything has to have very clean surfaces throughout. Dirt particles on the optics will start absorbing energy. That is very relevant for these types of sources.  So the laser module itself has to be done very precisely, with no obstructions. But even for the white light part, it's still pretty high density. But at the end of the day, we have guidelines for optics design and how to handle the source and, so far, it seems to be working okay. In most of these applications – especially in automotive – we end up in a sealed unit.  The whole headlight module is very well sealed so there's really no contamination.

LED professional: How do you think this will end up in the future? Will you manufacture the module or would it be possible to hand over the technology, the lasers and phosphors and then tell the buyers to design the module themselves?

Julian Carey: We're pretty clear on our strategy largely because of Dr. Nakamura's vision of lighting. We are dedicated as a lighting component manufacturer. Will we end up doing some pure laser applications? I believe so, just because the technology is so strong and so interesting for bio-medical or sensing or material processing, 3D printing – whatever! Those things will be part of our business but the company focus and its identity is regarding lighting. All specialty lighting, including automotive, is always going to be very important for us. We may integrate even further up through the chain with the inclusion of more optics from the standpoint of electronic beam control. Dynamic beam, basically, for various applications. The nice thing is that those technologies are very complimentary with laser. The whole system works better when you have a very tight beam. We definitely don't expect to become a licensing company or anything like that. We want to fill our fabrication facility and make lots of lasers and modules.

LED professional: Your understanding of the module is the laser LED and conversion. Does it also include optics?

Julian Carey: No, we don't really include any optics. When the module goes to a company, like BMW, they do their own optics. We have recommendations for partners, suppliers and design approaches. The nice thing about LEDs coming before us is a lot of the infrastructure and capabilities have already been put in place. That's why we work so hard trying to fit our technology into the standards. For example, we just got UL certification on the SMD device – which is the UL-8750 LED standard for how you handle it electrically, how you do different things optically and safety and all that kind of stuff. We are also certified for various automotive, IEC and IATF, standards. Basically, we just want to make a product that looks like what the market is already accustomed to, but works particularly well for certain applications like spotlights and high intensity.

Julian Carey speaks frankly about the topics that concern laser lighting technologies

LED professional: How big is the module and what is the wattage?

Julian Carey: The fiber module has two pieces connected with a fiber optic cable – which I believe is about 30 cm. Both elements are about the same size, so the laser module is about one cubic centimeter. The phosphor head is a flat piece that is about 2cm x 1cm. A lot of that robustness is for things like heat sinking in the automotive application. The SMD is 7mm x 7mm, so it really is an LED sized device. It's very, very compact. And each of those devices is about 400 - 500 lumen and consumes about 12 watts. Lumen per watt is still less than LEDs but we expect to climb rapidly in efficiency over the years and become comparable.

LED professional: So that's twelve watts in one cubic centimeter.

Julian Carey: Yes, exactly. But these are all metal body parts so heat sinking and thermal management is a really important point. Our efficiency is always about light placement at distance – so basically the capability to put lux at a faraway point. Not total lumens per watt or things like that where, obviously, LEDs excel to a huge degree, today. But when you combine those two things, there can be interesting future applications, too. One difference is that LEDs have droop – with the increasing current they lose their efficiency – lasers don't have that drawback, so as we keep making better and better laser chips, we can keep going to higher and higher powers on a single platform, which has economic benefits.

LED professional: Shuji Nakamura's approach was building GAN on GAN. Is it the same with laser? Theoretically, you would have the same opportunities.

Julian Carey: Yes, we are a GAN on GAN platform. We even use some of the equipment that was basically built for SORAA LEDs. In the wafer processing and build up from epi to wafer fab, some of the earlier steps are similar or almost identical. So we have the same kind of economy to scale potential there, if not more so because our chips are smaller. Architecturally, once you go to the final part of the fab, things diverge quite a bit. SORAA is doing a top-emitting chip. They're also doing 405 nanometer as emission spectrum. SLD has been once again standardized to 450 nanometers, driving conventional phosphors. Everything is the same, just a higher intensity level. Also, laser chips are side emitters so they're treated a little bit differently.

Laser fiber modules are currently the most powerful laser lighting solutions

LED professional: Keeping in mind what future developments will be, where do you see the laser in the next couple of years?

Julian Carey: We are a complementary technology to solid-state lighting. There aren't really any ways that LEDs can do some of the applications that we do, particularly with injection into fiber optic cable, for example, or very tiny cable transports or very tiny optics or extremely long throw distances like one thousand meters for a high beam. Those are things that lasers are clearly excelling at. Surly projection displays is an own whole application itself. LEDs want to become more intense but they're reaching their limits when it comes to efficiency, capabilities, materials and the droop problem. So there's only one or two percent a year that they can advance, where we are still increasing all of our parameters fifteen to twenty percent per year.

So how do we see laser technology developing: It's going to be more products, higher lumen capability per module, to do more jobs. Four or five hundred lumen sources are nice for various applications but all of a sudden, we see some of our customers combining six, ten, twelve units because a lot of lighting applications need more light. You may think about search and rescue, or entertainment lighting or stage lighting. 1000 lumen is sort of where things start for a source to be really useful and then it goes up quickly to 5000 or more. That's where we want to develop our source. We don't necessarily need to go to higher luminance – although the advantage there is still very large – but we'd just like to give more lumens per module. We also want to develop into architectural lighting. But we're still at 6000 Kelvin as a color temperature. So we need to have a major thrust in order to develop a warmer color temperature, at least to the sweet spot of commercial lighting at 4000 Kelvin. That's going to take another year, at least.

LED professional: What's the challenge to go to warmer color temperatures?

Julian Carey: One limitation is that the red phosphors are not as robust as the YAG yellow ones. So how do we combine them in the high temperature materials that bind phosphors together? We aren't using silicone things, they would burn really fast. So it all has to be ceramic based for these intensities. Red phosphors don't lend themselves well to that and it's not clear how to combine them. We are working very hard on getting them integrated. At least you don't need too much red or too much other warm colors to bring the net to 4000 Kelvin, I believe. 2700 is going to be a huge challenge, but I think for commercial lighting we'll be able to get there.

LED professional: That also means that currently, you can't go into areas where a high CRI is important. The advantage there is still on the side of the LED and if I understand it correctly, this probably won't change over the next few years.

Julian Carey: It's one of the challenges that we have. We have a clear mission ahead of us, in that regard because that's a major challenge. I think "outdoor" is looking very good but to get "indoor", like museum spots, or even just commercial track lighting, it would be nice to have warm color temperature track lighting with liquid crystal lens technology to modify the beam pattern. That would be a great complimentary system – but we would need to warm up the beam and get the CRI at least to a commercial lighting standard.

LED professional: That sounds like a lot of R&D work. Do you do all of your own R&D or do you network?

Julian Carey: All of our R&D is homegrown. It's Dr. Nakamura and his team that he's developed.

LED professional: But he is also at the university. Are they also involved in the research?

Julian Carey: It's really all on SLD laser. The only partnership I would call an R&D support partnership is the University of California.

We're even developing our own phosphor approach using raw materials. At least at the module level we have the expertise and experience to develop those aspects. But we partner with optics makers and thermal management companies and electronics to make the rest of the system.

SMD lasers are the latest development and while less efficient than LEDs in respect to lm/W in their application, it is a huge improvement with good prospects

LED professional: We know that people are a little afraid of laser when it comes to safety. And with good reason when you think about increasing the power – so are there special safety technologies? Are you certified as in regards to the safety standards?

Julian Carey: One of the reasons we have UL certification for 8750 is that we have several failsafe aspects to our designs. For the fiber module, the first and foremost is that, if, for example, you disconnected the metal phosphor head, you would now have a bare fiber. However, we have a photo diode detector in the module to detect the failsafe. And then you know that something has been damaged or somebody is actually tampering with the system to make it into a laser. With the SMD, it's more of a case of what happens if, for some reason, there is no phosphor?  That's where we have absorbing surfaces and beam blocks. The laser is actually facing inwards and would no longer be able to generate a laser beam exiting the part. And tampering with the SMD would basically destroy the part. You can have these failsafe systems for reflective phosphor architecture whereas most LEDs are a transmission architecture.  So if you took a knife and you took off the phosphor, and then you have blue light – that's not the case with our devices. We always have the light directed inwards and it works pretty well.

LED professional: Another question I forgot to ask earlier: I've heard that the driver for a laser is simpler to design than a driver for an LED – is that true?

Julian Carey: It can be in some ways. One of the nice features of the laser is that we see very linear behavior. Once you drive above a threshold, you have a near perfect relationship between current and light output. The only major difference to LEDs is that lasers have a threshold current, so they don't actually begin amplification until current reaches a certain threshold. So up to the threshold you basically have a regime where the device is not really producing light, but drawing current. In your PWM architectures, you want to stay on the linear portion because you can't really dim into the sub-threshold region, because then you'll get very strange behavior like flicker and things like that. So that's the difference. LEDs start from zero and then go up and up. But there is an L shaped curve for lasers. It's a subtle difference but meaningful if you're trying to modulate the part.

LED professional: That means that if I need a dimmer solution for a general lighting application, I always have to use a modulated signal.

Julian Carey: Yes, that's right. It's an interesting but subtle point.

LED professional: Since lasers are used in so many really fast applications that you would have a very high frequency for that and then you could avoid the unwanted effects.

Julian Carey: You're right. And response times for lasers are very, very fast and so, a future area of development or at least conceptual exploration right now is LiFi and how lasers could contribute to communication over line of sight.  Either vehicle to vehicle or within the built environment. The laser portion – the blue portion – can be modulated extremely fast.

LED professional: But isn't phosphor slowing it down?

Julian Carey: Yes, it is.

LED professional: One more question about the road map. What will we see next year? What will we see two years from now? What will happen later on?

Julian Carey: We have two roadmaps: Automotive and Specialty Lighting. Next year, I guess, in automotive we'll see an increase in lumens to the fiber module architecture. So maybe a 1000 lumen source next year and a 2000 lumen source the following year coupled with dynamic capabilities. Most of the work right now is going into integrating an ultra-bright source into dynamic reflectivity and optics. So that's what we'll see, probably late 2019, if not the following year: Dynamic architectures that combine laser, phosphor, high intensity lighting, but also with MEMS mirrors and LC optics that can shift the beam pattern.
For specialty lighting, next year, we should also see a 1000 lumen SMD and within one to two years we should see a 4000 Kelvin shift of the whole product line. Those are the kind of main priorities. And that's enough work!

LED professional: If you move that fast in your developments, how large is the proportion of researchers and developers in your company?

Julian Carey: I would say, that out of 120 people, we still have, as far as R&D and product development go, probably about eighty people – or two thirds of the company. We don't have an extensive sales and marketing department. We're not like companies like Osram or Lumileds at this point. We have about four people around the world that work with our customers. But now we're increasing the size of our operational group, which has been very small until the last three or four months. Now we need to coordinate a lot of production – bringing that discipline and control to the process rather than being solely R&D.  We have to make way for "the same way every day" rather than "a different way every day", which is what we've done up until now.

LED professional: Thank you very much for providing these really interesting insights into laser technology!

Julian Carey: Thank you for the opportunity to talk about these topics!

Julian Carey
Julian Carey is the Product and Technical Marketing Manager at SLD Laser, a leader in the commercialization of laser light sources for automotive and specialty lighting applications. At SoraaLaser, Julian oversees product strategy and marketing for new laser based light sources. In his prior role, Julian acted as head of marketing at Intematix, a leading innovator of phosphors and remote phosphor components for high-quality LED lighting. His previous roles were marketing and developing scanning laser based display systems at Prysm and LED based lighting components and systems at Philips, Lumileds and Agilent. He holds a BS degree in Mechanical Engineering from Stanford University and an MBA from MIT Sloan.