Powerful vacuum UV lamps poised to herald new era in photochemistry

A team of researchers from the Laboratory for Optical Physics and Engineering (LOPE) and Eden Park Illumination has created a series of flat, thin lamps that produce unprecedented levels of optical power in the vacuum ultraviolet region of the electromagnetic spectrum. 

The vacuum ultraviolet exists at extremely high frequencies on the electromagnetic spectrum. These frequencies of light do not travel far through air because they are absorbed by air very quickly. The reason this region is known as the “vacuum ultraviolet” is that early experimentalists found they had to pump all the air out of the system for light to propagate at these frequencies.

With the invention of these lamps, for the first time there exists a source that is capable of producing over 800 W of peak power and 25-30 W of average power at these high frequencies. The efficiency of this new, flat lamp technology is remarkable at more than 20%. Average powers above 1 kW can be produced by tiling about 40 - 50 lamps together. In the past, the output power from similar lamps has been extremely low.

“I’ve spent my life in the ultraviolet and the sheer power produced by these lamps is staggering. What has been available in the past has been on the order of milliwatts, if that,” said Professor James Gary Eden. Eden is also affiliated with the Coordinated Science Lab and the Micro and Nanotechnology Lab.

The lamps are mere 4”x4” squares and only 0.6 cm in thickness. However, these tiny lamps are capable of producing more than 25 W of power at a wavelength of 172 nm.

The photon energy at this wavelength is capable of rupturing most chemical bonds. The team believes that the production of these lamps will herald a new era in photochemistry. 

These lamps have several applications. If you were to take one of these lamps and turn it on in a room, within seconds you would be overwhelmed by the smell of ozone. Ozone (O₃) is generated when a 172 nm photon is absorbed by oxygen. 

Many more applications are being pursued, including using the lamps as disinfectants. The photon energies are so high that they can kill pathogens. While pathogens often become resistant to chemical disinfectants, they cannot build a resistance to high-energy photons. 

The lamps can also be used to detect the difference between natural and synthetic diamonds very quickly. If you take a natural diamond and shine the vacuum ultraviolet light on it, the diamond will emit a soft blue. If the same is done on a synthetic diamond, the light emitted will be a bright bluish-green. Therefore, you don’t have to be an expert in diamonds to detect artificial ones. All you need is this lamp.

Eden has been working with microplasmas since 1996. The development of these lamps evolved out of earlier work in large arrays of microplasmas. He and his students have been working on them for several years, perfecting the design process.

A patent application describing the lamp fabrication process is pending, and the key steps involve making arrays of microcavities in silica and then sealing thin sheets of silica together with a high temperature material known as frit. 

The lamps are being manufactured by a company in Champaign: Eden Park Illumination, which Eden co-founded with ECE ILLINOIS Adjunct Professor Sung-Jin Park. While the actual fabrication of the lamps occurs at Eden Park Illumination, the research from which the lamps have sprung came from the LOPE. 

This research has been published in an APL (Applied Physics Letters) paper, co-authored by Park, Dr. Andrey Mironov, Eden, Dr. Cy Herring and Dr. Jin Cho.