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Scientists demonstrate the world’s first continuous wave laser diode deep ultraviolet laser diode at room temperature

Scientists demonstrate the world’s first continuous wave laser diode deep ultraviolet laser diode at room temperature

Scientists demonstrate the world’s first continuous wave laser diode deep ultraviolet laser diode at room temperature

For the first time in the world, scientists have demonstrated continuous wave lasing of a deep ultraviolet laser diode at room temperature. Credit: Issey Takahashi

A research group led by 2014 Nobel laureate Hiroshi Amano at Nagoya University’s Institute of Materials and Systems for Sustainability (IMaSS) in central Japan, in collaboration with Asahi Kasei Corporation, has successfully performed the world’s first laser continuous wave at room temperature. – ultraviolet laser diode (wavelength up to the UV-C region).

These results, published in Applied Physics Lettersrepresent a step towards the widespread use of a technology with the potential for a wide range of applications, including sterilization and medicine.

Since their introduction in the 1960s, and after decades of research and development, the successful commercialization of laser diodes (LD) has finally been achieved for numerous applications with wavelengths ranging from infrared to blue-violet. Examples of this technology include optical communication devices with infrared LDs and Blu-ray discs using blue-violet LDs.

However, despite the efforts of research groups around the world, no one has been able to develop deep ultraviolet LDs. A key breakthrough occurred only after 2007 with the advent of technology to produce aluminum nitride (AlN) substrates, the ideal material for growing aluminum gallium nitride (AlGaN) films for UV light emitting devices.

Demonstration of a continuous wave laser at room temperature. Credit: 2022 Asahi Kasei Corp. and Nagoya University

Starting in 2017, Professor Amman’s research group, in collaboration with Asahi Kasei, the company that provided the 2-inch AlN substrates, began the development of a deep ultraviolet LD. Initially, injecting sufficient current into the device was too difficult, preventing further development of UV-C laser diodes.

But in 2019, a research group successfully solved this problem using a polarization-induced doping technique. For the first time, they produced a short-wavelength ultraviolet-visible (UV-C) LD that operates with short current pulses. However, the input power required for these current pulses was 5.2 W. This was too high for continuous wave lasing as the power would cause the diode to heat up quickly and the lasing would cease.

Scientists demonstrate the world’s first continuous wave laser diode deep ultraviolet laser diode at room temperature

Researchers who have successfully performed the world’s first room-temperature continuous-wave deep-ultraviolet laser diode. Credit: 2022 Asahi Kasei Corp. and Nagoya University

But now researchers from Nagoya University and Asahi Kasei have redesigned the structure of the device itself, reducing the drive power needed to operate the laser to just 1.1 W at room temperature. Earlier devices were found to require a high level of operating power due to the impossibility of effective current paths due to crystal defects occurring in the laser strip. But in this study, the researchers found that a strong crystal voltage creates these defects.

By cleverly tailoring the sidewalls of the laser strip, they suppressed defects, achieving efficient current flow to the active area of ​​the laser diode and reducing operating power.

Nagoya University’s industrial-academic collaboration platform, called the Center for Integrated Research on Future Electronics, Transformative Electronic Objects (C-TEFs), has enabled the development of new UV laser technology. Under C-TEF, researchers from partners such as Asahi Kasei share access to state-of-the-art facilities on Nagoya University’s campus, providing them with the people and tools needed to build high-quality, reproducible devices.

Zhang Ziyi, a representative of the research team, was in his second year at Asahi Kasei when he became involved in establishing the project. “I wanted to do something new,” he said in an interview. “At the time, everyone assumed that a deep ultraviolet laser diode was impossible, but Professor Amano told me, ‘We’ve got the blue laser, now it’s time for the ultraviolet’.”

This research is a milestone in the practical application and development of semiconductor lasers in all wavelength ranges. In the future, UV-C LDs could be applied in healthcare, virus detection, particle measurement, gas analysis, and high-def. laser processing.

“Its application to sterilization technology could be revolutionary,” Zhang said. “Unlike current LED sterilization methods, which are time-inefficient, lasers can disinfect large areas in a short time and over long distances.” This technology could especially benefit surgeons and nurses who need sterilized operating rooms and tap water.

The successful results were published in two papers in Applied Physics Letters.

More information:
Hiroshi Amano et al, Local strain control to suppress dislocation formation for pseudomorph-grown AlGaN UV-C laser diodes, Applied Physics Letters (2022). DOI: 10.1063/5.0124512

Hiroshi Amano et al., Key Temperature Dependent Characteristics of an AlGaN-Based UV-C Laser Diode and Demonstration of a Continuous Wave Laser at Room Temperature, Applied Physics Letters (2022). DOI: 10.1063/5.0124480

Citation: Scientists demonstrate world’s first room-temperature continuous-wave deep-ultraviolet laser diode lasing (2022, November 24) Retrieved November 24, 2022, from https://phys.org/news/2022-11-scientists-world- continuous-wave-lasing-deep-ultraviolet.html

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