Kaai takes laser productions to new planes

A small start-up grabbed headlines at this year’s Consuming Electronics Show (CES) with a claim for the longest wavelength, continuous-wave (CW) nitride laser. And there is good reason to believe that this firm will remain in the spotlight of the technical press for the rest of the year, because it plans to imminently launch on to the market what could well be the first violet, blue and green nitride lasers built on semi-polar and non-polar planes.

Kaai’s portfolio of blue and green lasers can target many different markets, including displays, such as Laser TVs. Credit: Mitsubishi

The name of this firm – Kaai – may not ring any bells, but its founders are certainly familiar. They are the University of California, Santa Barbara academics Shuji Nakamura, Stephen DenBaars and Jim Speck, who formed this spinoff shortly after collaborating to give the world its first ever non-polar laser.

This triumvirate hit that particular milestone on 29 January 2007, and then went on to further develop the technology, file patents, and lay the foundations needed to launch a spin-off company. It all came together in early 2008, and during the last two years the team at Kaai has been busy assembling a fabrication facility capable of everything from epitaxial growth through to finished products, and putting this resource to good use by developing a laser portfolio.

Kaai is testing the reliability of its blue and green lasers. Blue lasers have already showed lifetimes of up to 5000 hours

For most of that time the company has been operating in stealth mode. “Our view is that seeing is believing,” explains Paul Rudy, VP of Marketing and Sales. “Once we could physically show the laser to people, and once we had a road map for commercialization, we thought that it was the right time to go public.” He believes that the visible laser market has suffered from tremendous hype surrounding low-cost green sources, which are typically based on second harmonic generation (SHG), and he hopes that Kaai can combat any lingering skepticism by under promising and over delivering.

At CES Kaai unveiled a 523 nm CW laser delivering 2-3 mW, and since then it has also reported a 521 nm, 9 mW laser plus a 525 nm device producing 6 mW. Other devices in the company’s portfolio include a “world class” 405 nm CW device with a single-mode output of 0.5W and a wall-plug efficiency of 25 percent, and a 450 nm, single-mode laser that is also claimed to deliver worldclass powers and efficiencies.

Although this is a very impressive set of results, Kaai’s longest wavelength laser, which emits at 525 nm, is still a few nanometers short of Sumitomo’s record. Last summer this Japanese company reported 531 nm emission from a device driven in pulsed mode with a duty cycle of 0.5 percent. However, Rudy points out that there is a major difference between running a laser in a low-duty-cycle pulsed mode and operating it continuously: “The first step to creating a diode laser is to get lasing in pulsed mode, which is generally one-tenth of a percent duty cycle. It’s an important step, but in that regime the devices are not very useful.” Although some applications do employ pulsedriven lasers, their duty cycle is in a completely different regime - typically 30-40 percent, according to Rudy. Getting the devices to operate in this regime - or to deliver a CW output - requires a significant reduction in operating voltage alongside a hike in efficiency.

Building a team

Company founders Nakamura, Speck and DenBaars all spend about a day a week at Kaai, which is located in Goleta, a small city 8 miles west of Santa Barbara. The company’s future is now in the hands of Richard Craig, a CEO with a strong track record in growing the revenue of III-V start-ups. “He was CEO of Santur and grew that company from zero to $100 million, and executive VP of SDL, from the very early days until the acquisition by JDSU,” explains Rudy. Craig has put together a team of about 25 staff, including veterans involved with engineering, marketing and business development.

Laser diode expertise within Kaai’s ranks includes experience in the manufacture of both AlGaAs-based and InP-based lasers. In addition, Craig has also signed-up some former UCSB researchers, including James Raring, director of engineering, who were quick to jump at the chance to commercialize the technology that they had helped to create. Finance is in the hands of a finance start-up expert, who is a Silicon Valley start-up veteran, and business development is lead by Rudy, who can draw on his experience gained by a decade at Coherent, followed by a few years at QPC Lasers.

Start-ups needs more than just great technology, and securing the financial backing needed to bring ideas to market can be particularly tricky in the current economic climate. But Kaai has made very light weather of this challenge, thanks to a great relationship with venture capitalist Kholsa Ventures. “My understanding is that the Santa Barbara group and the Khosla group had been following one another’s work, and [early 2008] was just the right time to form the company,” says Rudy. Once a deal had been struck, the fabrication of the facility followed very quickly, and the company was making lasers by summer 2008.

Different foundations

Switching growth from the polar planes used by today’s leading semiconductor laser manufacturers to semi-polar and non-polar ones that Kaai is exploiting is reported to deliver several benefits: either the elimination or substantial reduction of internal electric fields that hamper light emission; the opportunity to increase quantum well thickness and introduce new structures for light guiding; and the potential to cut laser growth times.

Rudy thinks that all of these gains are beneficial, but says that the biggest one of all is the far greater choice of device design. “That design freedom may be on different architectures, it could be on different materials – there’s just a lot more freedom across the board.” Kaai’s engineers are already exploiting these advantages, and seeing higher efficiencies and powers from their single-mode lasers. Their efforts to date also indicate that yields for non-polar and semipolar devices will be better than those for conventional nitride lasers. One of the major choices facing Kaai’s engineering team is whether to work with a non-polar substrate for a particular laser design, or select a semi-polar plane. And if they select the latter, then there is the question of which particular plane. Rudy, however, is not divulging any secrets relating to that key decision-making process: “As a small company with great ambition to grow and commercialize this technology, we’ll be keeping a lot of cards to our chest.”

Kaai recently came out of stealth mode after developing CW, singlemode green lasers. These include a 6 mW laser at 525 nm, and a 9 mW version at 521 nm

Up until now, most of the pioneering work on non-polar and semi-polar devices has been carried out using substrates that are no bigger than a fingernail. This is not a barrier to trailblazing researchers, but it is a significant headache for anyone wishing to manufacture lasers in reasonable volume. This issue surrounding substrates was a big concern when the company was founded, but it now has a solution, which it is keeping under wraps. “I think [that the issues surrounding substrates] are a major barrier to entry for folks that want to enter this market and don’t know their way around, and don’t understand the technology,” says Rudy.

Multiple markets

The potential markets for Kaai’s products can be divided into existing markets currently served by other classes of laser, and new opportunities serving emerging applications. Markets that are buying blue and green lasers today include defense, biomedical, therapeutic medical, industrial and instrumentation, and these could all benefit from the lower cost that a single chip laser promises to deliver.

Since its launch in early 2008, Kaai has made rapid progress in extending the wavelength of its nitride lasers

“Some segments may be elastic and the world doesn’t know that yet, because it’s tough to explore that potential opportunity if you’ve got a three stage laser with an infrared pump and two crystals,” says Rudy.

Another opportunity for Kaai’s lasers exists in specialty lighting that demands high spatial brightness. Even a niche in that very large market is substantial. And on top of that, non-polar and semi-polar lasers could be used in laser displays, such as laser TV and pico projectors.

“The pico side has a lot of potential,” says Rudy. “SHG lasers have some technology out there, but manufacturers don’t seem to be in a position to ramp production.” Kaai’s long-term commercial success could rely on a strong patent portfolioto to protect the company’s IP. This US start-up has addressed this issue by licensing critical technology from UCSB, and then moving on to establish its own patent portfolio. “All the founders, as well as the many folks that have come onboard, are really aware of how to build IP portfolios in this space,” says Rudy. “It’s a big area of attention for us.”

Kaai has set itself several short-term goals, including the sampling of products in the first half of this year, followed by production in the latter half. In 2011 it will aim to ramp production, grow volume, and work hard to fulfill customer expectations. The plan is to offer both blue and green lasers, and the company is particularly excited about applications requiring both types of source.

One area of focus for the company is optimizing the efficiency of its 525 nm lasers, because potential customers are telling Kaai that 525nm is “green enough”. They say that they would rather start to receive product at that wavelength, than wait for the next generation 532 nm source to be developed. But in the longer term Kaai wants to extend the wavelength range of its products.

“My sense is that customers may want another 5 to 10 nm to get to 532 nm,” says Rudy, who admitted that progress from 520 nm onwards is particularly challenging.

In addition, the company will direct efforts at increasing the power and efficiency of its lasers. If it executes on all these fronts, then the success that follows will change the perception of non-polar and semi-polar lasers from just interesting devices for the lab to a commercially competitive technology.