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Optical Isolator Selection Guide
The following selection guides display Thorlabs' Optical Isolators. Click on any of the colored bars below to see full specifications and purchasing options for the chosen wavelength range and isolator type. For more details on the design and function of our isolators, see the Isolator Tutorial tab above. For isolator specification combinations not offered below, Thorlabs offers custom isolators with a wide range of center wavelengths, operating temperatures, package sizes, and various other specifications. Please see the Custom Isolators tab above for more details or to request a custom isolator.
Our Free-Space Isolators are available in fixed and adjustable narrowband options, as well as broadband and tandem options. For more information on differences between types of free-space isolators, see the Isolator Types tab above.
Our Fiber Isolators are available with SM or PM fiber. Our broadband SM fiber isolators, including those centered at 840 nm and 895 nm, are designed for use with superluminescent diodes (SLDs).
Optical Isolator Tutorial
An isolator's function is based on the Faraday Effect. In 1842, Michael Faraday discovered that the plane of polarized light rotates while transmitting through glass (or other materials) that is exposed to a magnetic field. The direction of rotation is dependent on the direction of the magnetic field and not on the direction of light propagation; thus, the rotation is non-reciprocal. The amount of rotation β equals V x B x d, where V, B, and d are as defined below.
Figure 1. Faraday Rotator's Effect on Linearly Polarized Light
β = V x B x d
V: the Verdet Constant, a property of the optical material, in radians/T • m.
B: the magnetic flux density in teslas.
d: the path length through the optical material in meters.
An optical isolator consists of an input polarizer, a Faraday rotator with magnet, and an output polarizer. The input polarizer works as a filter to allow only linearly polarized light into the Faraday rotator. The Faraday element rotates the input light's polarization by 45°, after which it exits through another linear polarizer. The output light is now rotated by 45° with respect to the input signal. In the reverse direction, the Faraday rotator continues to rotate the light's polarization in the same direction that it did in the forward direction so that the polarization of the light is now rotated 90° with respect to the input signal. This light's polarization is now perpendicular to the transmission axis of the input polarizer, and as a result, the energy is either reflected or absorbed depending on the type of polarizer.
Figure 2. A single-stage, polarization-dependent isolator. Light propagating in the reverse direction is rejected by the input polarizer.
The Forward Mode
In a dual-stage isolator, the light exiting the output polarizer is sent through a second Faraday rotator followed by an additional polarizer in order to achieve greater isolation than a single-stage isolator.
The Reverse Mode
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Figure 3. A single-stage, polarization-independent isolator. Light is deflected away from the input path and stopped by the housing.
Polarization-Independent Fiber Isolators
The Forward Mode
In a dual-stage isolator, the light then travels through an additional Faraday rotator, half-wave plate, and birefringent beam displacer before reaching the output collimating lens. This achieves greater isolation than the single-stage design.
The Reverse Mode
Figure 4. Pulse Dispersion Measurements Before and After an IO-5-780-HP Isolator
τ: Pulse Width Before Isolator
τ(z): Pulse Width After Isolator
Fixed Narrowband Isolator
The isolator is set for 45° of rotation at the design wavelength. The polarizers are non-adjustable and are set to provide maximum isolation at the design wavelength. As the wavelength changes the isolation will drop; the graph shows a representative profile.
Adjustable Narrowband Isolator
The isolator is set for 45° of rotation at the design wavelength. If the usage wavelength changes, the Faraday rotation will change, thereby decreasing the isolation. To regain maximum isolation, the output polarizer can be rotated to "re-center" the isolation curve. This rotation causes transmission losses in the forward direction that increase as the difference between the usage wavelength and the design wavelength grows.
Adjustable Broadband Isolator
The isolator is set for 45° of rotation at the design wavelength. There is a tuning ring on the isolator that adjusts the amount of Faraday rotator material that is inserted into the internal magnet. As your usage wavelength changes, the Faraday rotation will change, thereby decreasing the isolation. To regain maximum isolation, the tuning ring is adjusted to produce the 45° of rotation necessary for maximum isolation.
Fixed Broadband Isolator
A 45° Faraday rotator is coupled with a 45° crystal quartz rotator to produce a combined 90° rotation on the output. The wavelength dependences of the two rotator materials work together to produce a flat-top isolation profile. The isolator does not require any tuning or adjustment for operation within the designated design bandwidth.
Tandem isolators consist of two Faraday rotators in series, which share one central polarizer. Since the two rotators cancel each other, the net rotation at the output is 0°. Our tandem designs yield narrowband isolators that may be fixed or adjustable.
Click to Enlarge
Custom Isolator Example
Custom Adjustable Narrowband Isolator with Different Input and Output Polarizers Optimized for 650 nm Wavelength and 40 °C Temperature.
OEM Application Services
OEM and Non-Standard Isolators
In an effort to provide the best possible service to our customers, Thorlabs has made a commitment to ship our most popular free-space and fiber isolator models from stock. We currently offer same-day shipping on more than 90 isolator models. In addition to these stock models, non-stock isolators with differing aperture sizes, wavelength ranges, package sizes, and polarizers are available. In addition, we can create isolators tuned for specific operating temperatures and isolators that incorporate thermistors with heating or cooling elements for active temperature control and monitoring. These generally have the same price as a similar stock unit. If you would like a quote on a non-stock isolator, please fill out the form below and a member of our staff will be in contact with you.
Thorlabs has many years of experience working with OEM, government, and research customers, allowing us to tailor your isolator to specific design requirements. In addition to customizing our isolators (see the OEM Application Services list to the right), we also offer various application services.
We are able to provide a wide range of flexibility in manufacturing non-stock, free-space isolators. Almost any selection of specifications from our standard product line can be combined to suit a particular need. The table to the right shows the range of specifications that we can meet.
We offer isolators suitable for both narrowband and broadband applications. The size of the housing is very dependent on the desired maximum power and aperture size, so please include a note in the quote form below if you have special requirements.
We offer Faraday rotators center wavelengths from 532 nm to 1550 nm. These are the same components used to make our isolators and rotate the polarization of incoming light by 45°. Please contact Tech Support if you require a faraday rotator with a rotation angle or center wavelength outside of the aforementioned specifications.
Thorlabs is uniquely positioned to draw on experience in classical optics, fiber coupling, and isolators to provide flexible designs for a wide range of fiber optic specifications. Current design efforts are focused on increasing the Maximum power of our fiber isolators at and near the 1064 nm wavelength. We offer models with integrated ASE filters and taps. The table to the right highlights the range of specifications that we can meet.
The fiber used is often the limiting factor in determining the Maximum power the isolator can handle. We have experience working with single mode (SM) and polarization-maintaining fibers (PM); single-, double- and triple-clad fibers; and specialty fibers like 10-to-30 µm LMA fibers and PM LMA fibers. For more information about the fiber options available with our custom isolators, please see the expandable tables below.
In the spectral region below 633 nm, we recommend mounting one of our free-space isolators in a FiberBench system. A FiberBench system consists of pre-designed modules that make it easy to use free-space optical elements with a fiber optic system while maintaining excellent coupling efficiency. Upon request, we can provide select stock isolators in an optic mount with twin steel dowel pins for our FiberBench systems, as shown to the left.
We are also in the process of extending our fiber isolator capabilities down into the visible region. For more information, please contact Technical Support.
Custom Fiber Isolator
Custom Free-Space Isolator for Wavelengths Below 633 nm
Click to Enlarge
Twin Steel Pins Insert into FiberBench
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Make to Order Options
The expandable tables below provide information on some common isolator and rotator specials we have manufactured in the past. We keep the majority of the components for these custom isolators in stock to ensure quick builds, so these specials are available with an average lead time of only 2-4 weeks. Please use the Non-Stock Isolator Worksheet below for a quote.
Request a custom isolator quote using the form below or by contacting us for more information at (973) 300-3000.