UV Optical Filters - New Capabilities

UV Gain Flattening Filter

UV Gain Flattening Filter

July 23, 2012

Omega Optical are now able to deposit the UV oxide coating material, ZrO2, using their new equipment. The ZrO2 material transmits in the UV down to 250nm, and has excellent refractive index properties in the visible range.

The material’s transmitting ability combined with Omega new equipment translates into the fact that Omega now able to provide filters in the UV, as blue as 250nm, with higher transmissions, steeper edges, and deeper blocking than ever before. Moreover, since ZrO2 maintains an index of refraction of close to 2.2 throughout the visible range, these UV filters can be blocked to 700nm without the use of metals.

Omega optical have produced filters with 5 decade blocking slopes as low as 2%. This means that the coating will transition from 50% of peak to OD5 in 2% of the 50% of peak wavelength. For example, a 10nm wide filter at 350nm will have an edge a 355nm and will achieve OD5 only 7nm away at 362nm.

Omega optical have successfully executed five cavity Fabry-Perot designs, creating a 10nm wide band at 350nm with over 70% transmission. Higher phase thickness designs giving narrower passband are possible. They anticipate production of 5nm wide filters, blocked to 700nm, with peak transmissions that range from 40% at the 280nm up to over 75% at 400nm.

In addition, they have made wider bandpass filters with even higher transmission. The details of such filter are: 350BP40 filter with OD5 at 323nm and 382nm, blocked to 700nm with > 80% transmission.

For extended blocking, they can incorporate their UV gain flattening filter, which may extend the blocking to the FIR while still providing transmission as high as 40%.

What are your challenges with UV optical filters?
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