Scientists have developed a new type of nano-level LED that can be transformed into a micro laser

April 14, 2021

[ Instrument network instrument research and development ] A new type of light-emitting diode (LED) developed by a team of scientists from the National Institute of Standards and Technology (NIST) may be the key to overcoming the long-term limitation of light source efficiency. This concept was demonstrated in the laboratory with micro-LEDs, achieving a significant increase in brightness and the ability to generate laser light-all these characteristics make it extremely valuable in large-scale and miniaturized applications.

The team also includes scientists from the University of Maryland, Rensselaer Polytechnic Institute, and IBM Thomas J. Watson Research Center. Their research is published in the peer-reviewed journal "Science Advances," and the paper describes their work in detail. The display brightness of their device is 100 to 1000 times higher than the traditional sub-micron LED design.

"This is a new architecture for manufacturing LEDs." said Babak Nikoobakht of NIST, who conceived this new design. "We use the same materials as traditional LEDs. Our difference lies in their shapes."

LED lights have existed for decades, but the development of bright LEDs won the Nobel Prize and ushered in a new era of lighting. However, even modern LEDs have their limitations, which makes their designers frustrated. To a certain extent, increasing the power of the LED will make it lighter, but the brightness will soon decrease, making the efficiency of the LED very low. This problem, called "efficiency drop" by the industry, hinders the application of LEDs in many promising application fields, from communication technology to antivirus.

Although the researcher's new LED design overcomes the problem of reduced efficiency, the researcher was not initially rushing to solve this problem. Their main goal is to create a miniature LED for very small applications, such as the laboratory-on-chip technology that scientists at NIST and elsewhere are pursuing.

The research team conducted a new design experiment on the part of the light-emitting LED: Unlike the graphic design used in traditional LEDs, the researchers used a long and thin zinc oxide wire to create a light source, which they called a fin. ("Long" and "thin" are relative terms: each fin is only about 5 microns long, about one-tenth the width of the average human hair.) Their fin array looks like a small comb, which can extend to An area of 1 cm or more.

"We saw business opportunities in the fins, because I think their slender shape and larger sides may be able to receive more current." Nikoobakht said, "In the beginning, we just wanted to measure how much the new design can withstand. The pressure. We started to increase the current and wanted to burn it out, but it got brighter and brighter."

The researchers’ new design can emit bright wavelengths that span the border between violet and ultraviolet light, generating 100 to 1000 times the energy of a typical small LED. Nikoobakht described this result as an important fundamental discovery.

He said: "A typical LED with an area less than 1 square micron has a luminous power of about 22 nanowatts, but this LED can generate up to 20 microwatts of power." "This shows that this design can overcome the drop in LED efficiency. Make the light source brighter."

"This is one of the most effective solutions I have seen." said Grigory Simin, a professor of electrical engineering at the University of South Carolina who was not involved in the project. The organization has been working on improving the efficiency of LEDs for many years, and other methods often encounter technical problems when applied to sub-micron wavelength LEDs. This method is very effective. "

While increasing the current, the research team also found another surprising discovery. Although the LED initially emits light in one wavelength range, its relatively broad emission eventually narrows to two wavelengths of intense purple. Simply put: their miniature LEDs have become miniature lasers.

"It takes a lot of effort to convert an LED into a laser. It usually requires coupling the LED with a resonant cavity so that light is reflected around the resonant cavity to generate laser light. It seems that the fin design can do the whole work by itself, without adding another A cavity."

A miniature laser is essential for chip-scale applications not only in the field of chemical sensing, but also in the next generation of handheld communication products, high-definition displays, and disinfection.

"It has a lot of potential to become an important component." Nikoobakht said, "Although this is not the smallest laser that people make, it is very bright. If the efficiency does not drop, it will be useful."

Author:

Mr. WeiFeng Zhang

Phone/WhatsApp:

+8618037058088