FGL550M Dia. 25 mm SM1-Mounted Colored Glass Filter; 550nm Longpass

The FGL550M is a color glass filter developed by Thorlabs, a leading vendor in the optical industry. This filter, with a catalog number FGL550M, is specifically designed for use in optical systems that require longpass filtering at 550nm. The filter is mounted in an SM1-compatible design, ensuring ease of integration into various optical systems.

The FGL550M filter has a circular geometry with a diameter of 25 mm and a thickness of 2 mm. The base shape of the filter is made of n-BK7 Schott, a high-quality optical glass known for its excellent transparency and low auto-fluorescence. This material makes the filter suitable for a wide range of applications, including biomedical imaging, fluorescence microscopy, and laser systems.

The filter's primary function is to cut on at 550nm, allowing wavelengths longer than this to pass through while blocking shorter wavelengths. The cut-off wavelength is 0nm, meaning it allows all wavelengths longer than 550nm to pass through. This longpass characteristic makes it ideal for applications where longer wavelengths need to be isolated or emphasized.

The filter's coating is another crucial aspect of its design. Both the front and back surfaces of the filter are coated with the THo FGL550 coating, which enhances its longpass performance. This coating ensures high transmission for wavelengths longer than 550nm and low reflection at the coating interface.

In terms of shape, the FGL550M filter is designed as a thin lens. This shape not only facilitates easy integration into optical systems but also minimizes optical aberrations, ensuring the highest quality of optical transmission.