High-power, free-space optical isolators are available from AMS Technologies with typical peak isolations starting from 35 dB and an average optical power handling up to 80 W:
- Models providing 35 dB peak isolation and capable of handling optical powers up to 30 W average or up to 30 kW pulse peak (free space optical isolators).
- Models providing 40 dB typical isolation and with up to 80 W average handling optical powers (high-power free space isolators). These isolators allow to mount your own fiber pigtailed collimator or beam expander. Tilt adjustment techniques enable optical alignment by the user. They come with built-in windows (easily removable and replaceable by the user) to prevent dust contamination of internal isolator optics.
Both optical isolator series comprise polarization sensitive as well as polarization insensitive devices. In addition to free space optical isolators, AMS Technologies also offers isolators for fiber optic applications.
Our optical isolators can be used with our various lasers and light sources as well as with further components out of our portfolio of precision optics, including optical lenses, optics assemblies, optical filters, optical prisms, optical mirrors, optical beamsplitters, etalons, optical gratings and polarization optics as well as optical scanners and deflectors or optical modulators, q-switches and pockels cells.
For mounting, adjusting and moving our optical components with high precision, we carry an array of optomechanics and motion control such as optical mounts, rotary and translation stages plus motion controllers as well as optical tables, breadboards and platforms.
Optical isolators are devices that transmit light only in one direction, but deflect and possibly block or absorb light in the opposite direction. Optical isolators are often used to block lasers from unwanted back reflections, which can influence the laser power or damage the laser due to feedback. In addition to free space optical isolators, fiber optic isolators are also available.
Optical isolators use the Faraday effect: an optically inactive material becomes optically active when an external magnetic field is applied and rotates the polarization of the light. In an optical isolator, the strength of a Faraday rotator’s magnetic field is adjusted so that the polarization of the light is rotated by exactly 45°.
Polarization-sensitive optical isolators feature two polarization filters at each end of the magnetized material that are rotated 45° to each other. Now, the light coming from one direction is rotated 45° so that it can pass through the rear polarization filter (the analyzer) unhindered. Light coming from the opposite direction, however, is rotated by an additional 45° so that it now strikes the front polarization filter perpendicularly. It is thus not transmitted, but (in the case of polarization prism cubes) reflected to the side. Due to their construction, the insertion loss of polarization sensitive optical isolators depends on the input beam’s polarization.
Polarization-insensitive optical isolators, on the other hand, show a constant insertion loss for incident light of any polarization. Instead of simple polarizing filters, polarization-independent isolators feature birefringent wedges at the input and output that spatially separate the polarization components of the incident light beam that are perpendicular to each other and – after rotation by the common Faraday rotator – recombine them into the output. Reflected light – also independent of its polarization – is not blocked but scattered and deflected by the birefringent wedges in such a way that both beam’s orthogonal polarization components exit the input wedge in the opposite direction with a lateral offset as well as diverted. Thus, the reflected light does hardly interfere with the input beam.
Since the Faraday rotation of light depends on the wavelength, optical isolators only work in a defined wavelength range – outside of this wavelength range, a major part of the light is also transmitted in the opposite direction and part of the light in the forward direction is filtered out by the analyzer.
High-power optical isolators must allow for a sufficiently large beam area, and their maximum tolerable optical power is also limited by thermal effects such as heating due to parasitic absorption, thermal lensing or depolarization.
Among an optical isolator’s most important properties are the operational wavelength range, the degree of isolation (loss of optical power in the reverse direction, given in dB), insertion and return loss as well as the maximum average or peak power the isolator is able to transmit – and if the device is polarization sensitive or insensitive.
Alternative Terms: Free Space Isolator; High-power Free Space Isolator; Faraday Isolator; Optical Diode