Knight Optical Helps Meet Heightened Demand for UVC Disinfection Applications

Ultraviolet (UV) light – and, more specifically, UVC light between 200 and 280nm – has been used for germicidal irradiation for decades, primarily in laboratories, medical facilities, and water treatment. However, since the novel coronavirus, COVID-19, became a worldwide pandemic, with each new variant bringing fresh concerns, there has come a demand to make this technology accessible and affordable for public sectors, including transportation and hospitality, to help day-to-day life return to normality in a safe environment.

UV disinfection systems come in a variety of different forms. Still, all have the same end goal of inactivating pathogens in the air, water, or on surfaces by exposing them to a controlled amount of shortwave radiation which damages the DNA within the cell.

To produce a system, a UVC light source needs to be used that works within this 200 to 280nm range. Ordinarily, this would be a mercury lamp transmitting at 254nm. Yet, this wavelength poses its own risks to humans, as it penetrates through skin and eyes and damages human cells alongside any bacteria and viruses. However, research has shown that far-UVC wavelengths between 207 and 222nm still inactivate pathogens but do not penetrate deep enough into active skin layers¹ to damage human cells. This means that there has been a shift in developing far-UVC sterilisation systems in recent years as they can be operated safely by humans and used in high-traffic areas. KrBr and KrCl excimer lamps would be used, rather than a mercury lamp, with operating wavelengths of 207nm and 222nm, respectively.

These UV disinfection systems require optical components that transmit, or reflect, within these UVC and far-UVC wavelengths. Knight Optical, an established supplier of optical components, has successfully built a portfolio of optics that do just that. From Windows and Lenses to Domes and Optical filters, we can provide stock and custom-made solutions to help you with your application.

The substrate of the optical component is essential, and there are limited options with high transmission within the UVC region.

The most common materials for UV applications are:

• UV Fused Silica (UVFS): is frequently used as it is cost effective to produce and very durable
• Calcium Fluoride (CaF₂): has a wide transmission band from 130nm and transmits over 90% within the UVC waveband
• Magnesium Fluoride (MgF₂): has very similar transmission properties to CaF_2, but it is more durable and resistant to water. It is often used in vacuum ultraviolet (VUV) and UV applications, where it is cut in such a way as to minimise the birefringence it can exhibit.
• Sapphire (Al₂O₃): is highly durable, being the second hardest mineral after diamond. Its transmission is lower than that of CaF₂ and MgF₂ but still has a transmission above 80% at 200nm onwards.

Knight Optical stock optical components manufactured from all these materials, including:

• UVFS Windows and Domes
• CaF­₂ Windows and Lenses
• MgF₂ Windows
• Sapphire Lenses and Random-Cut and C-Cut

If our stock components do not fulfil your requirements, we can also provide custom optics manufactured to your individual specifications. This includes different dimensions, materials, and, if required, the application of an optical coating – such as an antireflective (AR) coating to enhance its performance, for example.

Optical Filters, such as Bandpass and Shortpass varieties, are also key components within these disinfection systems. For example, a Bandpass Filter can be designed to have a centre wavelength within the far-UVC whilst blocking above 230nm and, therefore, ensuring that any harmful UV light does not exit the system.

Knight Optical makes it a priority to supply ready-to-order Bandpass Filters that cover these specific wavelengths. What’s more, our stock catalogue now includes mounted Interference Bandpass Filters in 25 and 35mm diameters with centre wavelengths (CWLs) between 214 and 320nm.

At Knight Optical, we test each optical component against its specification within our on-site, state-of-the-art metrology laboratory. The facility is equipped with a wide range of instruments to measure the different parameters on an optic.

This includes:

• Zygo Verifire XPZ interferometer: for measuring surface form, such as irregularity, flatness, and transmitted wavefront distortion. We also use the interferometer for radial measurements on optical lenses.
• Trioptics OptiSpheric and OptiCentric: for radius, focal length, and centring error measurements
• Agilent Cary 7000 spectrophotometer: for spectral measurements, with the ability to check coatings at multiple angles of incidence and different polarisation states

Furthermore, all optics are also 100% visually inspected before packaging, by our QA staff, who are trained to ISO 10110 and MIL-0-13830A.

The technical sales team at Knight Optical work closely with our customers to ensure they are providing both a high-quality product and service. Please do send your enquiries through to the Knight Optical team on the below details.

Europe, UK, Asia & RoW: info@knightoptical.co.uk

+44 (0)1622 859444
USA & Canada: usasales@knightoptical.com
+1 401-583-7846

www.knightoptical.com

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