Faraday Optical Isolator, Broadband, 5 mm Aperture, 720-950 nm

The Broadband isolators use high damage threshold polarizing beamsplitter (PBS) cubes and provide double escape ports for added application flexibility.

Strong Neodymium Iron Boron permanent magnets are used to generate >10,000 Gauss axially-oriented fields within the magnet housing. The strong longitudinal field causes 45 degrees of non-reciprocal polarization rotation for propagating light via the Faraday Effect in the Terbium Gallium Garnet (TGG) crystal located within the magnet housing. Following the TGG crystal is a quartz reciprocal rotator with 45 degrees rotation. In the forward direction, the two rotations add up, resulting in 90 degrees of rotation. In the reverse direction, the two rotations are opposite and result in 0 degrees of rotation. The change in rotation as the wavelength shifts from the central wavelength is similar for both TGG and quartz, resulting in broadband operation. In operation, the magnet housing is sandwiched between input and output polarizers that have their transmission axis oriented 90 degrees relative to each other. In the reverse direction the backward traveling beam has a polarization orthogonal to the input polarizer and is therefore crossed with it, resulting in a rejected beam exiting the input polarizer.

The YIG crystal utilized in our Faraday isolators creates a large Verdet constant that ultimately describes the strength of the Faraday effect and provides effective isolation of back-reflected light. Additionally, these isolators have low absorption as a function of the YIG crystal and polarizers, resulting in reliable transmission of light in the forward direction.