Holonyak, Feng receive second patent for transistor laser

ECE Professors Nick Holonyak, Jr and Milton Feng, post doctoral researcher Gabriel Walter, and former post doctoral researcher Richard Chan have received a second patent for their invention of the world’s first transistor laser, a device that significantly changes the science and technology of lasers and introduces basic changes in the traditional transistor and what is known about its operation. The result is a fundamentally new transistor and a fundamentally new laser. The realm of high-speed communications could be significantly impacted by this discovery.

Along with two PhD students, Feng and Holonyak first began to modify fundamentally the transistor to encourage its generation of light by transistor operation (by the transistor effect). The researchers currently have $6.5 million in funding from DARPA through the Hyper-Uniform Nanophotonic Technology Center (HUNT) directed by ECE Professor K.Y. Norman Cheng.

At 60-years-old this month, the transistor is still changing and being taken in new directions. Holonyak said transistors have always been known as a potential light source—a weak source. “But Milton and I have pointed out to the world that the transistor, operating as a transistor, particularly a high-current-density, high-speed, heterojunction, bipolar transistor (an HBT) can generate light,” he said. “We just went back to fundamental principles and said, “This thing, to be doing what it’s doing, has to also be a light generator. So we decided to go looking for that light, and found it and introduced fundamental changes to make it into a strong source of light, a new form of laser.”  The transistor laser is a new device, with new structural elements and new operational elements.

Holonyak said that while they were looking for the light, they found more than they expected. “Now this has gone way beyond what anyone anticipated,” he said.

Their high-speed, high-current-density transistor has certain modifications and extensions that also make it a three-terminal laser operating at a frequency of more than 10 GHz, according to Holonyak. With an electrical input and output, as well as optical output, the three-terminals make it a one-of-a-kind discovery. “It’s a true transistor and a true laser,” he said. “No lasers are three-terminal except this one.”

Feng considers this three-port transistor with light-emitting capabilities to be a significant advancement in technology. “We think the transistor laser is one of the major breakthroughs [in technology],” he said. In fact, Holonyak said he thinks this may be the most important advancement he’s seen on the engineering campus in his many years here. In 2006, Feng and Holonyak’s research paper describing the transistor laser was voted one of the five most important papers published by Applied Physics Letters in over 40 years.

Holonyak said when working with semiconductors and transistors, you are inevitably in the world of items that people make and sell. “If the superconductor went away, such as we know it to be today, hardly a man on the street would know it. But if the semiconductor went way…,” Holonyak paused. “Uh oh. Calamity. So the scale [of transistors] in terms of the practical world is unimaginable. In the world of electronics, the transistor is everything. In terms of how much it controls in the electronics world, according to the dollar amount of what people use, it’s unimaginable.”

Holonyak said he doesn’t know if anything on the engineering side and the technical side of the scale he’s talking about in the College of Engineering has happened of this magnitude since the BCS Theory of Superconductivity.

“Working with the semiconductor for 55 years, I’ve seen a lot of good things,” said Holonyak. “We have done something to the transistor that makes it bigger than it ever was before,” he continued. “There’s still a lot more to unearth in terms of the understanding of how it’s doing what it’s doing and also to take it into the realm where you can do practical things with it. That’s why we’re filing patents. Milton and I cannot imagine all the things that will come out of this. In terms of the perspective on the things I’ve seen along the way, this is as big as it gets.”

Feng said they began discussions on the transistor laser in 2003 as part of HBT studies and completed the first demonstration in 2004. Their first patent for the transistor laser was filed in February 2005 and issued in 2006. A third patent is nearing its final processing phase, four or five others are in various stages of allowance in the patent office, and two have just been filed. In total, the body of work will generate more than 10 patents, which could take years to complete.

“The great value [of the transistor laser] is that it has a variety of possibilities,” said Holonyak. “And you don’t know which ones are going to be the most important until you do more building. It’s an ongoing thing in the world of ideas about how to work with ideas and stretch ideas and look at them again.”