Broadband Fiber Isolators for SLDs

  • Flat Isolation Over a 100 nm or 150 nm Wavelength Range
  • Available Center Wavelengths: 840 nm, 895 nm, 950 nm, 1064 nm
  • Ideally Suited for Use with SLDs
  • OEM and Build-to-Order Fiber Isolators Available


(No Connectors)

Connectors Available Upon Request

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Selection Guide for Isolators
(Click Here for Our Full Selection)
Fiber Isolators
Spectral Region Wavelength Range Fiber Type
Visible 650 - 670 nm SM
NIR 770 - 1060 nm SM
Nd:YAG 1064 nm SM
IR 1290 - 2010 nm SM
Fiber Isolators for Broadband SLDs
Free-Space Isolators
Custom Isolators

Custom Isolators

  • Customizable Wavelength, Aperture, Max Power, Housing, Polarizers, and Operating Temperature
  • Pricing Similar to Stock Units
  • Wide Range of OEM Capabilities
  • Please Contact Tech Support or See Our Custom Isolators Page


  • Flat, ≥23 dB Isolation over a Broad Wavelength Range is Ideal for SLDs
  • Minimize Feedback into Optical Systems
  • Operating Wavelength Ranges of 790 - 890 nm, 820 - 970 nm, 900 - 1000 nm, or 1014 - 1114 nm
  • 0.8 m to 1 m of Fiber Built in to Each Side of the Isolator
  • Unterminated Fiber Pigtails (Connectors Available by Contacting Tech Support)
  • Each Unit is Individually Tested
  • Polarization-Independent Design

Fiber isolators protect light sources from back reflections and signals that can cause intensity noise and optical damage. Optical isolators, also known as Faraday isolators, are magneto-optic devices that preferentially transmit light in the forward direction while absorbing or displacing light propagating in the reverse direction (see the schematic below). Please see the Isolator Tutorial tab for an explanation of the operating principles of a Faraday isolator.

Light Propagation Through a Polarization-Independent Isolator
Click for Details

Polarization Independent Isolator Schematic
Light is deflected away from the input path and stopped by the housing. See the Isolator Tutorial tab for more information. Click the schematic to show polarization states.

The IO-F-SLD Series Polarization-Independent Broadband Fiber Isolators are specifically designed for use with superluminescent diodes (SLDs). Typical fiber isolators have a narrow operating wavelength range with a peak isolation of about 33 dB. The isolators on this page are designed for flatter isolation over a broader wavelength range of either 100 nm or 150 nm, depending on the model, but have a lower isolation of 23 dB. This wider operating band makes them an ideal choice for broad-spectrum devices like SLDs. These polarization-independent models are designed for use with CW light sources only and come with 780HP or HI1060 single mode fiber with unterminated, scissor-cut fiber ends.

There is 0.8 m to 1 m of fiber built in to each side of the isolator, and an arrow on the body indicates the transmission direction. In addition, each unit is tested before shipment to ensure compliance with our specifications and a complete test report comes with every serialized part.

Optical Isolator Tutorial

An optical isolator is a passive magneto-optic device that only allows light to travel in one direction. Isolators are used to protect a source from back reflections or signals that may occur after the isolator. Back reflections can damage a laser source or cause it to mode hop, amplitude modulate, or frequency shift. In high-power applications, back reflections can cause instabilities and power spikes.

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.


Faraday Effect in an Isolator Drawing
Click to Enlarge

Figure 1. Faraday Rotator's Effect on Linearly Polarized Light

Faraday Rotation

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.


Drawing of Light Propagation Through an Isolator
Click to Enlarge

Figure 2. A single-stage, polarization-dependent isolator. Light propagating in the reverse direction is rejected by the input polarizer.

Polarization-Dependent Isolators

The Forward Mode
In this example, we will assume that the input polarizer's axis is vertical (0° in Figure 2). Laser light, either polarized or unpolarized, enters the input polarizer and becomes vertically polarized. The Faraday rotator will rotate the plane of polarization (POP) by 45° in the positive direction. Finally, the light exits through the output polarizer which has its axis at 45°. Therefore, the light leaves the isolator with a POP of 45°.

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
Light traveling backwards through the isolator will first enter the output polarizer, which polarizes the light at 45° with respect to the input polarizer. It then passes through the Faraday rotator rod, and the POP is rotated another 45° in the positive direction. This results in a net rotation of 90° with respect to the input polarizer, and thus, the POP is now perpendicular to the transmission axis of the input polarizer. Hence, the light will either be reflected or absorbed.


Light Propagation Through a Polarization-Independent IsolatorClick for Details
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 polarization independent fiber isolator, the incoming light is split into two branches by a birefringent crystal (see Figure 3). A Faraday rotator and a half-wave plate rotate the polarization of each branch before they encounter a second birefringent crystal aligned to recombine the two beams.

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
Back-reflected light will encounter the second birefringent crystal and be split into two beams with their polarizations aligned with the forward mode light. The faraday rotator is a non-reciprocal rotator, so it will cancel out the rotation introduced by the half wave plate for the reverse mode light. When the light encounters the input birefringent beam displacer, it will be deflected away from the collimating lens and into the walls of the isolator housing, preventing the reverse mode from entering the input fiber.


General Information

Damage Threshold
With 25 years of experience and 5 U.S. patents, our isolators typically have higher transmission and isolation than other isolators, and are smaller than other units of equivalent aperture. For visible to YAG laser Isolators, Thorlabs' Faraday Rotator crystal of choice is TGG (terbium-gallium-garnet), which is unsurpassed in terms of optical quality, Verdet constant, and resistance to high laser power. Thorlabs' TGG Isolator rods have been damage tested to 22.5 J/cm2 at 1064 nm in 15 ns pulses (1.5 GW/cm2), and to 20 kW/cm2 CW. However, Thorlabs does not bear responsibility for laser power damage that is attributed to hot spots in the beam.

Autocorrelation Measurement of Isolator IO-5-780-HP
Click to Enlarge

Figure 4. Pulse Duration Measurements Before and After an IO-5-780-HP Isolator

The magnet is a major factor in determining the size and performance of an isolator. The ultimate size of the magnet is not simply determined by magnetic field strength but is also influenced by the mechanical design. Many Thorlabs magnets are not simple one piece magnets but are complex assemblies. Thorlabs' modeling systems allow optimization of the many parameters that affect size, optical path length, total rotation, and field uniformity. Thorlabs' US Patent 4,856,878 describes one such design that is used in several of the larger aperture isolators for YAG lasers. Thorlabs emphasizes that a powerful magnetic field exists around these Isolators, and thus, steel or magnetic objects should not be brought closer than 5 cm.

The magnets and the Faraday rotator materials both exhibit a temperature dependence. Both the magnetic field strength and the Verdet Constant decrease with increased temperature. For operation greater than ±10 °C beyond room temperature, please contact Technical Support.

Pulse Dispersion
Pulse broadening occurs anytime a pulse propagates through a material with an index of refraction greater than 1. This dispersion increases inversely with the pulse width and therefore can become significant in ultrafast lasers.

τ: Pulse Width Before Isolator

τ(z): Pulse Width After Isolator

τ = 197 fs results in τ(z) = 306 fs (pictured to the right)
τ = 120 fs results in τ(z) = 186 fs

Optical Isolator in FiberBench Mount
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

  • Direct Integration to Laser Head Assemblies
  • Combination Isolator and Fiber Coupling Units
  • Minimum Footprint Packages
  • Filter Integration
  • Active Temperature Control and Monitoring
  • Feedback Monitoring
  • Environmental Qualification
  • Private Labeling
  • ITAR-Compliant Assembly

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.


Parameter Range
Wavelength Range From 365 - 4550 nma
Aperture Sizes  Up to Ø15 mm
Polarization Dependence Dependent or Independent
Max Powerb Up to 2 GW/cm²
Isolation Up to 60 dB (Tandem Units)
Operating Temperature 10 - 70 °C
  • Custom Faraday rotators, for use in the 365 to 5000 nm range, are also available.
  • The maximum power specification represents the maximum power for the combined forward and reverse directions. Therefore, the sum of the powers in the forward and reverse directions cannot exceed the maximum power specification.

Free-Space Isolators

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.


Faraday Rotators

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.


Parameter Range
Wavelength Range From 633 - 2050 nma
Polarization Dependence Dependent or Independent
Max Powerb (Fiber to Free-Space) 30 W
Max Powerb (Fiber to Fiber) 20 W
Operating Temperature 10 - 70 °C
  • For wavelengths shorter than 633 nm, we recommend using our free-space isolators in conjunction with our modular FiberBench accessories. Please contact Technical Support for more information.
  • The maximum power specification represents the maximum power for the combined forward and reverse directions. Therefore, the sum of the powers in the forward and reverse directions cannot exceed the maximum power specification.

Fiber Isolators

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

Optical Isolator in FiberBench Mount
Click to Enlarge

Twin Steel Pins Insert into FiberBench
Optical Isolator in FiberBench Mount
Click to Enlarge

Mounted Isolator
Polarization Independent Fiber
Polarization Maintaining Fiber


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.

Adjustable Narrowband Isolators
Faraday Rotators
Fixed Narrowband Isolators
Fixed Broadband Isolators


Custom Request Form

Request a custom isolator quote using the form below or by contacting us for more information at (973) 300-3000.

Non-Stock Isolator Worksheet:
Please select your input type:   Free-Space Input  |    Fiber Input
Is this an ITAR request?:   Yes  |    No     Not sure?
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ITAR (International Traffic in Arms Regulation) is a United States Government regulation controlling the import and export of defense-related articles on the United States Munitions List (USML). Information and material pertaining to military and defense related technology may only be shared with U.S. Persons unless authorization from the Department of State is received or a special exemption is used.
Free-Space Input
Wavelength or Wavelength Range (nm):
Power (W):
Max 1/e2 Beam Diameter (mm)*:
Isolation (dB):
% Transmission:
Fiber Input
Wavelength or Wavelength Range (nm):
Power (W):
Polarization Sensitivity:  Dependent   |     Independent
Isolation (dB):
% Transmission:
Fiber Connector:   FC/PC   |     FC/APC   |     Other
Output:   Fiber   |     Free-Space

Customer Information:
First Name*:
Last Name*:
Zip/Postal Code*:

Characters are Case-SensitiveClick for Details

Click for a new code.

Posted Comments:
Fabian Krabbe  (posted 2019-04-17 12:17:08.267)
I have a question concerning the insertion loss and the performance graph, specifically the transmission curve. Either I am making a mistake in the way I am thinking about them or there is a mistake. The definition for insertion loss is the ratio of input power to output power, which is the reciprocal of the transmission. When calculating the transmission from the stated insertion loss of any isolator, I get the maximum value for the transmission on the respective curve in the performance graph. This is confusing to me, as the stated insertion loss is supposed to be the maximum insertion loss over the isolator bandwidth, so it should lead to the minimum of the transmission instead of the maximum right? Because a lower transmission should mean a higher insertion loss. Is the graph just upside down, or am I interpreting something wrong? (is the stated insertion loss possibly only valid at the central wavelength?) Thanks Fabian
YLohia  (posted 2019-04-22 03:12:53.0)
Hello Fabian, thank you for contacting Thorlabs. The insertion loss spec is a maximum value while the transmission spec is a theoretical value. For example, for the IO-F-SLD100-840, the 1.6 dB insertion loss corresponds to 30.8% loss (note that we are referring to optical powers here which is calculated as 10*log(ratio), not electrical losses). The theoretical transmission value based on the plot is 69.2% for the center wavelength and thus the math works out. That being said, we normally build and test these isolators with an SLD whose center wavelength matches closely to that of isolator. We do also try single wavelength CW diodes in the operating range to test for insertion loss and isolation for validation and QC purposes.
yantengkui  (posted 2015-12-08 15:21:34.37)
the wavelength range of IO-F-SLD100-1064 in the spec table is 1064 ± 50 nm, but the product description appears 900 - 1000 nm, would they contradict with each other?
jlow  (posted 2015-12-08 08:57:21.0)
Response from Jeremy at Thorlabs: It seems the product description had a typo. We will get this corrected. The specification in the spec table is correct.
chienchunglee  (posted 2015-06-08 19:27:51.443)
What kind of fiber collimator is used for coupling in and out in these isolators? Do they have AR-coating? Is the fiber end cleaved at an angle? Thanks.
rwalz  (posted 2015-07-30 04:04:45.0)
Single mode angle polished AR coated fiber are used on the inputs and outputs. The standard angle is 8 degrees. Small AR coated aspheric lenses are used as the collimating and coupling lenses.

The following selection guide contains all of Thorlabs' Fiber Optical Isolators. Click the colored bars below to to see specifications and options for each wavelength range and isolator type. Please note that Thorlabs also offers free space optical isolators and custom optical isolators.

Optical_Isolator 940 nm PM
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Broadband Fiber Isolators for SLDs

Click Image to Enlarge IO-F-850 IO-F-895 IO-F-SLD100-950 IO-F-SLD100-1064
Item # IO-F-SLD100-840 IO-F-SLD150-895 IO-F-SLD100-950 IO-F-SLD100-1064
Polarization Independent Independent Independent Independent
Wavelength 840 ± 50 nm 895 ± 75 nm 950 ± 50 nm 1064 ± 50 nm
Max Powera 2 W (CW)
Isolationb ≥25 dB ≥23 dB ≥25 dB ≥25 dB
Performance Graph
(Click for Plot)
Click to View Click to View Click to View Click to View
Insertion Loss ≤1.6 dB ≤2.1 dB ≤1.5 dB ≤1.5 dB
Polarization Dependent Loss (PDL) ≤0.25 dB
Return Loss ≥52 dB ≥50 dB
Fiber 780HP HI1060
  • The maximum power specification represents the maximum power for the combined forward and reverse directions. Therefore, the sum of the powers in the forward and reverse directions cannot exceed the maximum power specification. Not recommended for high-power pulsed applications. The maximum power handling of this isolator is reduced with the addition of connectors.
  • Isolation at Center Wavelength
Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available
IO-F-SLD100-840 Support Documentation
IO-F-SLD100-840Customer Inspired! Fiber Isolator, 790 - 890 nm, SM, 2 W, No Connectors
Lead Time
IO-F-SLD150-895 Support Documentation
IO-F-SLD150-895Customer Inspired! Fiber Isolator, 820 - 970 nm, SM, 2 W, No Connectors
IO-F-SLD100-950 Support Documentation
IO-F-SLD100-950Customer Inspired! Fiber Isolator, 900 - 1000 nm, SM, 2 W, No Connectors
IO-F-SLD100-1064 Support Documentation
IO-F-SLD100-1064Customer Inspired! Fiber Isolator, 1014 - 1114 nm, SM, 2 W, No Connectors