New! Sign up for our free email newsletter.
Science News
from research organizations

A new way to create germ-killing light

Researchers at Osaka University create a new optical device that can be used to kill pathogens on surfaces while remaining safe for humans

September 11, 2023
Osaka University
A research team has created an aluminum-nitride device that can convert visible light into deep-ultraviolet light through the process of second harmonic generation. This work can lead to the development of practical devices that can sterilize surfaces with ultraviolet radiation while using less energy.

While it has long been known that ultraviolet (UV) light can help kill disease-causing pathogens, the COVID 19 pandemic has put a spotlight on how these technologies can rid environments of germs. However, the excimer lamps and LEDs that can directly emit light in the required deep-UV wavelengths generally have low efficiency or suffer from short lifetimes. Moreover, UV light of the wrong wavelength can actually be harmful to human cells.

Now, a team led by researchers from Osaka University has shown how an optical device made of aluminum nitride can be used to generate deep-UV light in a method wholly different from previous approaches. The team made use of a process called 'second harmonic generation,' which relies on the fact that the frequency of a photon, or particle of light, is proportional to its energy.

Most transparent materials are considered 'linear' with respect to their response to light, i.e., photons cannot interact with each other. However, inside certain 'nonlinear' materials, two photons can be combined into a single photon with twice the energy, and thus, twice the frequency. In this case, two visible photons can be merged into a single deep-UV photon inside an aluminum nitride waveguide less than one micron wide. A waveguide is a channel of transparent material with physical dimensions chosen so that light of desired frequencies can travel easily. The waveguide helps take advantage of the nonlinear optical properties of the material, so that second harmonic generation can occur with the highest efficiency.

"Our new fabrication method for deep-UV light generation borrows techniques from semiconductor processing, which allows for precise control of the orientation of the aluminum-nitride crystal. This was difficult to achieve in the past," explains lead author Hiroto Honda.

The wavelength of UV light created by the prototype device is within a very narrow range that has enough energy to kill germs but remains mostly harmless to humans.

"The results of our project help show that compactness and efficiency is possible for deep-UV disinfection tools, without sacrificing human safety," says senior author Ryuji Katayama. The researchers hope to refine this method to produce commercial devices that consume less energy than previous options.

Story Source:

Materials provided by Osaka University. Note: Content may be edited for style and length.

Journal Reference:

  1. Hiroto Honda, Soshi Umeda, Kanako Shojiki, Hideto Miyake, Shuhei Ichikawa, Jun Tatebayashi, Yasufumi Fujiwara, Kazunori Serita, Hironaru Murakami, Masayoshi Tonouchi, Masahiro Uemukai, Tomoyuki Tanikawa, Ryuji Katayama. 229 nm far-ultraviolet second harmonic generation in a vertical polarity inverted AlN bilayer channel waveguide. Applied Physics Express, 2023; 16 (6): 062006 DOI: 10.35848/1882-0786/acda79

Cite This Page:

Osaka University. "A new way to create germ-killing light." ScienceDaily. ScienceDaily, 11 September 2023. <>.
Osaka University. (2023, September 11). A new way to create germ-killing light. ScienceDaily. Retrieved December 7, 2023 from
Osaka University. "A new way to create germ-killing light." ScienceDaily. (accessed December 7, 2023).

Explore More
from ScienceDaily