A research team at the Institute of Materials and Systems for Sustainability (IMaSS) at Nagoya University, led by 2014 Nobel laureate Hiroshi Amano, collaborated with Asahi Kasei Corporation.
With the collaboration, he successfully realized the room temperature continuous wave laser of the world's first deep ultraviolet laser diode (wavelengths up to the UV-C region).
These findings, published in Applied Physics Letters, mark an important step towards the general use of a technology with the potential for multiple uses, such as sterilization and medicine.
Decades of research and development have taken place since their introduction in the 1960s.
Following these studies, laser diodes (LDs) have finally been successfully commercialized for a variety of applications with wavelengths ranging from infrared to blue-violet. Examples of this technology include Blu-ray discs using blue-violet LDs and optical communication devices using infrared LDs.
However, despite the efforts of research teams from around the world, no one has been able to create deep ultraviolet LDs. After 2007, the technology for forming aluminum nitride (AlN) substrates emerged, which is an excellent material for producing aluminum gallium nitride (AlGaN) film for UV light emitting devices.
Professor Amano's research team began work on deep ultraviolet LD in 2 in partnership with 2017-inch AlN substrate supplier Asahi Kasei. The development of UV-C laser diodes was initially discontinued. Because it was very difficult to feed enough current to the device.
But in 2019, the study team used a polarization-induced doping approach to successfully address this issue. They created a short wavelength UV-C LD for the first time using short current pulses to study. However, these current pulses required 5,2 W of input power. This power was too high as it would cause the diode to heat up in a short time and stop glowing, preventing continuous wave radiation.
The structure of the device was recently modified by scientists from Nagoya University and Asahi Kasei, reducing the driving force required for the laser to operate at just 1.1W at ambient temperature. It was discovered that because earlier devices could not provide efficient current paths due to crystal defects occurring in the laser strip, they needed a lot of power to operate. However, the researchers discovered in this study that it was strong crystal tension that caused these defects.
They successfully suppressed the defects, providing effective current flow to the active region of the laser diode and creatively adapting the sidewalls of the laser strip, reducing the operating power.
The Future Electronics Integrated Research Center, Transforming Electronics Facilities (C-TEFs), an industry-academic collaboration platform at Nagoya University, led to the creation of new UV laser technology.
C-TEFs gives researchers from organizations like Asahi Kasei access to state-of-the-art facilities on the Nagoya University campus, giving them the staff and resources they need to create reliable, high-quality devices.
Ziyi, a member of the research team, was a sophomore in Kasei when the project was founded. He said in an interview: “I wanted to do something unique. Deep ultraviolet laser diode was believed to be impossible at the time, but Professor Amano told me, "We've accomplished the blue laser, now it's ultraviolet time."
This work marks a milestone in the practical development and application of semiconductor lasers across all wavelength ranges. In the future, UV-C LDs can be used for high resolution laser processing, particle measurement, virus detection and gas analysis.
Zhang noted that the application to sterilization technology "could be revolutionary." “Unlike current time-inefficient LED sterilization methods, lasers can disinfect enormous areas in a short time and over long distances.” Nurses and surgeons who need sterile operating rooms and tap water can particularly benefit from this technique.
Günceleme: 27/11/2022 12:55