Filter technology for the Terahertz (mm and sub-mm) spectral region
We offer a unique multi-mesh filter technology which allows extremely precise wavelength selection. Our range has been developed over more than 30 years by our astronomical academic colleagues, and is now a cornerstone technology used in all major sub-millimetre and Terahertz astronomical projects on the ground and in space.
We offer the following types of filters:
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If you are interested in our filters, please contact us so that we can use our extensive experience to discuss the best solution to meet your requirements. You can see examples of the performance of our filters here; these are our standard filters, produced in quantity and often available in stock. These are the lowest cost option and we would look to provide these filters in the first instance. If these are not suitable, we can custom design filters to your precise requirements.
Both standard and custom designed filters can be produced to your choice of size and shape, with a maximum diameter of 300 mm.
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Properties of our filters include:
- High in-band transmission efficiency
- 90% transmission in a typical low-pass filter
- 80% peak transmission efficiency in band-pass filters
- Low absorption and scatter; almost all non-transmitted power is reflected
- High broadband out of band blocking
- High frequency definition
- Negligible polarisation sensitivity in transmission (at near normal incidence)
- Robust construction
- Clear aperture diameters from 6 to 300 mm.
- Operation from room temperature down to temperatures below 1 K (-272 °C).
- Operating wave numbers between 1 cm-1 (30 GHz, 10 mm) and 700 cm-1 (21 THz, 10 um)
The majority of our filters use a dielectric spacer to separate the meshes forming the filter; we refer to them as "hot-pressed" filters. Low frequency, hence thicker, filters can be provided as free-standing filters, and are available at any size up to 300 mm and in arbitrary shapes. The higher frequency filters are quite thin and are difficult to keep flat, hence we recommend that they be purchased ready mounted in a frame. We offer several standard frame sizes up to 120 mm outer diameter. If you require a size greater than this, please contact us and we will see what we can do. The large aperture30 GHz low pass filters manufactured for the Korean Astronomical Observatory (see picture) were up to 250 mm outer diameter.
On rare occasions, "air-gap" filters in which there is no dielectric spacer can be more suitable than hot-pressed filters; these can be provided if necessary, and we would advise you if we thought they would be appropriate for your application.
Our filter technology was originally developed for astronomical applications, where the need exists both for high in-band transmission efficiency and excellent out-of-band rejection in order to select the extremely low astronomical signal levels between intense atmospheric emission lines. An additional requirement of these filters is that they must cycle reliably between ambient and cryogenic temperatures for use with cooled bolometers and photodetectors, whilst maintaining their performance. These properties also make the filters of great value to the wider scientific community.