FSR-RG9 25.4 mm Dia. Colored Glass Absorptive Longpass Filter 725nm

The FSR-RG9 is a longpass filter, designed and manufactured by MKS/Newport, a renowned vendor in the field of optical elements. This filter is specifically designed for use in optical systems that require the selective blocking or passing of light within a certain wavelength range. The FSR-RG9 has a catalog number of FSR-RG9 and is available for purchase directly from the vendor's website, where it is currently listed as in stock.

The filter is circular in shape, with a diameter of 25.4 mm and a thickness of 3 mm, making it suitable for a wide range of optical applications. It is made from a specialized type of colored glass, which is known for its excellent absorptive properties. This material is identified in the item data as 'uvfs mal- 1965'.

The FSR-RG9 features a longpass cut-on wavelength of 725nm, meaning it begins to significantly attenuate light at this wavelength. However, it does not have a defined cut-off wavelength, instead, it gradually becomes more transmissive as the wavelength decreases. This is a common characteristic of absorptive filters and can be beneficial in certain applications where a gradual transition between blocked and transmitted light is required.

Both the front and back surfaces of the filter are coated with a layer of 'new rg9', which is likely a specialized coating designed to enhance the filter's performance. The exact nature of this coating is not specified in the item data, but it is common for optical filters to be coated to reduce surface reflections, improve transmission, or enhance wavelength selectivity.

The filter's shape is described as 'Thin Lens', suggesting it may have some degree of optical power, although this is not explicitly stated in the item data. Regardless, the FSR-RG9 is a versatile and high-performance longpass filter that is sure to be a valuable addition to any optical system.