UV Free-Space Isolators (365 - 385 nm)

  • Center Wavelength of 375 nm
  • Isolation up to 30 dB
  • 100 W/cm2 Power Density
  • Custom Isolators Available Upon Request


from Saddle



Shown in the SM1RC Saddle Mounted on an Optical Table Using a BA1 Base with an SD1 1/4"-20 to 8-32 Counterbore Adapter

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Tunable Isolation Curves
Click to Enlarge

Our Adjustable Narrowband Isolators can be tuned to maximize the peak isolation for any wavelength within a narrow spectral range (shaded in this graph). See the Wavelength Tuning tab for more details.

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


  • Minimize Feedback into Optical Systems
  • Free-Space Input and Output Ports
  • Tunable Wavelength Ranges
  • Isolation at Center Wavelength of 30 dB
  • Ø2.7 mm or Ø4.7 mm Max Beam Diameter (Model Dependent)
  • Polarization-Dependent Input

Thorlabs is pleased to stock these free-space optical isolators, which have been designed for use in the UV spectral range (365 - 385 nm). Optical isolators, also known as Faraday isolators, are magneto-optic devices that preferentially transmit light along a single direction, shielding upstream optics from back reflections. Back reflections can create a number of instabilities in light sources, including intensity noise, frequency shifts, mode hopping, and loss of mode lock. In addition, intense back-reflected light can permanently damage optics. Please see the Isolator Tutorial tab for an explanation of the operating principles of a Faraday isolator.

Selection Guide for Isolators
(Click Here for Our Full Selection)
Wavelength Range
365 - 385 nm (UV)
390 - 700 nm (Visible)
690 - 1080 nm (NIR)
1064 nm (Nd:YAG)
1110 - 2100 nm (IR)
2.20 - 4.55 µm (MIR)
Fiber Isolators
Custom Isolators

In the UV wavelength range, we offer adjustable narrowband isolators. These offer the user the ability to adjust the alignment of the input and output polarizers, allowing tuning of the center wavelength within a 10 nm range and an operation range of 20 nm. Please see the Isolator Types tab for additional design details and representative graphs of the wavelength-dependent isolation.

Each isolator's housing is marked with an arrow that indicates the direction of forward propagation. In addition, all isolators have engravings that indicate the alignment of the input and output polarizers.

Thorlabs also manufactures isolators for fiber optic systems and wavelengths extending into the infrared (see the Selection Guide table to the left). If Thorlabs does not stock an isolator suited for your application, please refer to the Custom Isolators tab for information on our build-to-order options, or contact Tech Support. Thorlabs' in-house manufacturing service has over 25 years of experience and can deliver a free-space isolator tuned to your center wavelength from 244 nm to 4.55 µm. Our vertically integrated manufacturing structure allows us to offer faraday rotators used in optical isolators. We offer a selection of faraday rotators from stock and can provide custom faraday rotators upon request.

Shaded regions on a graph represent the center wavelength tuning range of the isolator. With these isolators, the isolation and transmission curves will shift as the center wavelength shifts. Please note that these curves were made from theoretical data and that isolation and transmission will vary from unit to unit.

Tuning an Adjustable Narrowband Isolator

  • Optimize Our Isolators to Provide the Same Peak Isolation Anywhere Within Their Tuning Range
  • Simple Tuning Procedure, Illustrated Below, Consists Primarily of Rotating the Output Polarizer
  • Slight Transmission Losses Occur Due to Polarizer Rotation
Dependence of Transmission on Center Wavelength
Click to Enlarge
When the isolator is tuned away from its design wavelength, the maximum transmission falls because the output polarizer's transmission axis is not parallel to the polarization direction of the output light.
Tunable Isolation Curves
Click to Enlarge

Our Adjustable Narrowband Isolators can be tuned to maximize the peak isolation for any wavelength within a narrow spectral range (shaded in this graph).

Click to Enlarge

Light Not at the Design Wavelength is Partially Transmitted

Click to Enlarge

Light at the Design Wavelength is Rejected

Operating Principles of Optical Isolators
Thorlabs' Adjustable Narrowband Isolators are designed to provide the same peak isolation anywhere within a 20 - 40 nm tuning range. They contain a Faraday rotator that has been factory tuned to rotate light of the design wavelength by 45°. Light propagating through the isolator in the backward direction is polarized at 45° by the output polarizer and is rotated by 45° by the Faraday rotator, giving a net polarization of 90° relative to the transmission axis of the input polarizer. Therefore, an isolator rejects backward propagating light. See the Isolator Tutorial tab for a schematic of the beam path.

The magnitude of the rotation caused by the Faraday rotator is wavelength dependent. This means that light with a different wavelength than the design wavelength will not be rotated at exactly 45°. For example, if 670 nm light is rotated by 45° (that is, 670 nm is the design wavelength), then 660 nm light is rotated by 46.5°. If 660 nm light is sent backward through an isolator designed for 670 nm without any tweaking, it will have a net polarization of 45° + 46.5° = 91.5° relative to the axis of the input polarizer. The polarization component of the light parallel to the input polarizer's axis will be transmitted, and the isolation will therefore be significantly reduced.

Since the net polarization needs to be 90° to obtain high isolation, the output polarizer is rotated to compensate for the extra rotation being caused by the Faraday isolator. In our example, the new polarizer angle is 90° - 46.5° = 43.5°. This adjustment increases the isolation back to the same value as at the design wavelength.

Consequences of Wavelength Tuning Procedure
As a direct consequence of rotating the output polarizer, the maximum transmission in the forward direction decreases. 660 nm light propagating in the forward direction is polarized at 0° by the input polarizer and rotated by 46.5° by the Faraday rotator, but the output polarizer is now at 43.5°. The amount of the transmission decrease can be quantified using Malus' Law:

Malus's Law
Malus' Law

Here, θ is the angle between the polarization direction of the light after the Faraday rotator and the transmission axis of the polarizer, I0 is the incident intensity, and I is the transmitted intensity. For small deviations from the center wavelength, the decrease in transmission is very slight, but for larger deviations, the decrease becomes noticeable. In our example (a 10 nm difference between the design wavelength and the usage wavelength), θ = 46.5° - 43.5° = 3.0°, so I = 0.997 I0. This case is shown in the graphs above.

In applications, the decrease in transmission caused by the tuning procedure is usually less important than the significantly enhanced isolation gained by tuning. For example, if the 670 nm isolator shown in the graphs above were used at 650 nm without tuning, the transmission would be 88.7% (instead of 88.0%), but the isolation would be only 25 dB (instead of 40 dB). This case is also shown in the graphs above.

Thorlabs' isolator housings make it easy to rotate the output polarizer without disturbing the rest of the isolator. Our custom isolator manufacturing service (see the Custom Isolators tab) can also provide an isolator specifically designed for a particular center wavelength, which can eliminate or strongly mitigate the transmission losses that occur at the edges of the tuning range. These custom isolators are provided at the same cost as their equivalent stock counterparts. For more information, please contact Technical Support.

Illustrated Tuning Procedure

To optimize the isolation curve for a specific wavelength within the tuning range, the alignment of the output polarizer may be tweaked following the simple procedure outlined below. Only a minor adjustment is necessary to cover a range of several nanometers. The procedure differs slightly for different isolator packages, but the principle remains the same across our entire isolator family, and complete model-specific tuning instructions ship with each isolator.

Step 1:
Orient the isolator in the backward direction with respect to the beam (i.e., with the arrow pointing antiparallel to the beam propagation direction). A power meter with high sensitivity at low power levels should be placed after the isolator.

Use the included 5/64" hex key to loosen the isolator from its saddle.

Step 2:
Grip the isolator by the sides and gently bring it out of its saddle. It is only necessary to bring it out far enough to expose the 8-32 setscrew at the top, as shown in the photo to the left.

Step 3:
Use the included 5/64" hex key to tighten the isolator back into its saddle with the 8-32 setscrew exposed.

The isolator is mechanically stable in this position as long as the isolator has not been brought forward too much. (The amount shown in the image to the left is safe by several millimeters.) It should therefore not be necessary to reinsert the isolator at the end of the tuning procedure.

Step 4:
Loosen the exposed 8-32 setscrew using the included 5/64" hex key. At this point, the output polarizer will be free to rotate.

Step 5:
Rotate the output polarizer to minimize the power on the power meter. As explained above, the necessary adjustment should be only a few degrees, depending upon the desired center wavelength. Tighten the 8-32 setscrew once optimization is achieved.

As long as the isolator was not brought forward too much at the end of Step 2, the isolator will be mechanically stable in this position. Attempting to reinsert the isolator at this point may cause misalignment.

Fixed Narrowband Isolation

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.

  • Fixed Rotator Element, Fixed Polarizers
  • Polarization Dependent
  • Smallest and Least Expensive Isolator Type
  • No Tuning

Adjustable Narrowband Isolation

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.

  • Fixed Rotator Element, Adjustable Polarizers
  • Polarization Dependent
  • General-Purpose Isolator

Adjustable Broadband Isolation

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.

  • Adjustable Rotator Element, Fixed Polarizers
  • Polarization Dependent
  • Simple Tuning Procedure
  • Broader Tuning Range than Adjustable Narrowband Isolators

Fixed Broadband

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.

  • Fixed Rotator Element, Fixed Polarizers
  • Polarization Dependent
  • Largest Isolation Bandwidth
  • No Tuning Required

Tandem Isolators

Tandem Isolators

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.

  • Up to 60 dB Isolation
  • Polarization Dependent
  • Highest Isolation
  • Fixed or Adjustable

Polarizer Types, Sizes, and Power Limits

Thorlabs designs and manufactures several types of polarizers that are used across our family of optical isolators. Their design characteristics are detailed below. The part number of given isolator has an identifier for the type of polarizer that isolator contains. For more details on how the part number describes each isolator, see the given isolator's manual. 

Polarizer Comparison
Type Schematic
(Click to Enlarge)
Maximum Power Density Description
Very Low Power 
VLP Polarizer 10 W/cm2 (CW, Blocking)
25 W/cm2 (CW, Transmission)
Our Very Low Power Absorptive Film Polarizers are compact options for isolating free-space beams. For light polarized perpendicular to the polarizer's transmission axis, the max power density is 10 W/cm2, while for light polarized parallel to the polarizer's transmission axis, the max power density is 25 W/cm2.
Very Low Power
(P or VLP)
VLP Polarizer 25 W/cm2 (CW, Blocking)
100 W/cm2 (CW, Transmission)
These polarizers are also for use with very low power sources but are made with a different material than the type C polarizers listed above. This gives these polarizers a higher maximum power density. For light polarized perpendicular to the polarizer's transmission axis, the max power density is 25 W/cm2, while for light polarized parallel to the polarizer's transmission axis, the max power density is 100 W/cm2.
Wire Grid
VLP Polarizer 25 W/cm2 (CW) Wire Grid Polarizers are used in our mid-IR isolators. They consist of a linearly spaced wire grid pattern that is deposited onto an AR-coated silicon substrate.
Polarizing Beamsplitter
PBS Polarizer 13 - 50 W/cm2 (CW) Polarizing Beamsplitter Cubes are commonly used in low-power applications and feature an escape window useful for monitoring or injection locking.
GLB Polarizer 100 W/cm2 (CW) Thorlabs' α-BBO Glan-Laser polarizers are all based on high-grade, birefringent, α-BBO crystals with a wavelength range of 210 - 450 nm. Due to the birefringent structure of α-BBO, a phase delay is created between two orthogonally polarized waves traveling in the crystal. These are similar to the High Power (HP) polarizers, but have a different escape angle.
Low Power
LP Polarizer 250 W/cm2 (CW)
25 MW/cm2 (Pulsed)
Our Low Power Polarizers are Glan-type, crystal polarizers, providing high transmission and power densities at the expense of a larger package than Very Low Power (VLP) and Polarizing Beamsplitter (PBS) polarizers.
Medium Power
MP Polarizer 100 W/cm2 (CW)
50 MW/cm2 (Pulsed)
Medium Power Polarizers are Glan-type, crystal polarizers, capable of handling higher powers. The rejected beam is internally scattered, which reduces the maximum power density, but also eliminates a stray beam from the setup.
High Power
HP Polarizer 500 W/cm2 (CW)
150 MW/cm2 (Pulsed)
High Power Polarizers are Glan-type, crystal polarizers, similar in size and transmission to Medium Power (MP) polarizers, but capable of handling higher powers. They feature an escape window suited for injection locking.
Yttrium Orthovanadate
HP Polarizer 25 W/cm2 (CW) YV polarizers are similar to the Medium Power (MP) Glan-type crystal polarizers; however, by using yttrium orthovanadate (YVO4) rather than calcite, YV polarizers can accommodate wavelengths in the 2.0 - 3.4 µm range. The rejected beam is internally scattered, which reduces the maximum power density, but also eliminates a stray beam from the setup.
Very High Power
VHP Polarizer 20 kW/cm2 (CW)
2 GW/cm2 (Pulsed)
Our Very High Power Polarizers are based on Brewster windows and feature the highest power handling possible. These polarizers have larger packages than HP-based designs, but are also more economical. All VHP-based designs also feature escape windows.

Video Insight: How to Align an Optical Isolator

To ensure optimal transmission of optical power from the source, as well as effective suppression of reflections traveling back towards the source, the Faraday isolator must be properly aligned. Alignment is demonstrated using an IO-3-532-LP polarization-dependent free-space isolator with a 510 nm to 550 nm operating range, an R2T post collar, a PL201 linearly polarized and collimated 520 nm laser, a S120C silicon power sensor, and a PM400 power meter.

If you would like more information about tips, tricks, and other methods we often use in the lab, we recommend our other Video Insights. In addition, our webinars provide practical and theoretical introductions to our different products.


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 244 - 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 244 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:
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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

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The following selection guide contains all of Thorlabs' Free-Space 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 fiber optical isolators and custom optical isolators.

Optical Isolators633 +/- 30660 -0/+10780 +/- 20850 +/- 20830 +/- 20980 +/- 201064 +/- 201050 +/- 201030 +/- 201310 -60+651550 +/- 50560 +/- 30532 -22/+18488 -18/+17440 +/-20405 -15/+20375 +/-10589 +/-20633 +/-30670 +/-30730 +/- 40780 +/-40850+/-40895 +/-40940 +/- 40980 +/-401030 +/-401050 +/-301064 -44/+361150 +/-401220 +/-401310 -60/+651390 +/-501480 +/-501550 +/-501650 +/-501850 +/-502050 +/-502300 +/- 502500 +/- 503400 +/- 504500 +/-501750 +/-501950 +/-50780 - 1000748 - 851650 - 980780 +/- 40670 +/-30633 +/-20850 +/-40980 +/-301064 -44/+361550 +/-50
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375 nm Polarization-Dependent Isolators

Click Image for Details IO-3-375-GLB IO-5-375-GLB
Item # IO-3-375-GLBa IO-5-375-GLBa,b
Type Adjustable Narrowband Adjustable Narrowband
Center Wavelength 375 nm 375 nm
Tuning Range 370 - 380 nm 370 - 380 nm
Operating Range 365 - 385 nm 365 - 385 nm
Transmissionc 70% 70%
Isolationc 30 dB (Min) 30 dB (Min)
Performance Graph
(Click for Details)
Click for Details Click for Details
Max Beam Diameterd 2.7 mm 4.7 mm
Max Powere 3 W 8 W
Max Power Density 100 W/cm2 100 W/cm2
Compatible Mounting
  • This isolator has two exit ports for rejected beams. Adequate beam traps should be selected and positioned to ensure safety.
  • The housing of this isolator cannot be freely rotated in its saddle. However, tapped holes in the housing allow the isolator to be mounted with the polarization axis either parallel or perpendicular to the base of the mount. If you require free rotation for your setup, consider using an SM3B2 or C2RC (C2RC/M) adapter (see below for details).
  • Specified at center wavelength. See Performance Graph for wavelength dependence.
  • Defined as containing 100% of the beam energy.
  • 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.
  • Please see below for further details.
  • One SM1RC with an 8-32 tap is included with this isolator. For an SM1RC/M with an M4 tap, please contact Tech Support prior to ordering.

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Simplified Mechanical Drawing

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Simplified Mechanical Drawing
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IO-5-375-GLB Isolator Mounted with the Polarization Axis Perpendicular to the Base of the Mount
Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Imperial Price Available
IO-3-375-GLB Support Documentation
IO-3-375-GLBCustomer Inspired! Free-Space Isolator, 375 nm, Ø2.7 mm Max Beam, 3 W Max
+1 Qty Docs Part Number - Universal Price Available
IO-5-375-GLB Support Documentation
IO-5-375-GLBCustomer Inspired! Free-Space Isolator, 375 nm, Ø4.7 mm Max Beam, 8 W Max
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Isolator Mounting Adapters

These adapters provide mechanical compatibility between our isolator bodies and SM2 (2.035"-40) lens tubes, SM3 (3.035"-40) lens tubes, 30 mm cage systems, Ø1/2" posts, or Ø1" posts.

Mounted Isolator
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IO-3-375-GLB Mounted in a CP36 30 mm Cage Plate
Click Image to Enlarge CP36 SM1RC SM1TC SM2A21 SM3B2 C2RC
Item # CP36 SM1RC(/M) SM1TC SM2A21 SM3B2 C2RC(/M)
Isolator Diameter 1.2" 1.2" 1.2" 1.2" 2.0" 2.0"
Mounting Options 30 mm Cage Systems Ø1/2" Posts Ø1/2" Posts SM2 Lens Tubes or Mechanics with Ø2" Bore SM3 Lens Tubes Ø1/2" Posts or
Ø1" Posts
Compatible Isolators IO-3-375-GLB IO-5-375-GLB
Limited Stock Icon

The SM3B2 will be retired without replacement when stock is depleted. If you require this part for line production, please contact our OEM Team.

Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Imperial Price Available
C2RC Support Documentation
C2RCSlip Ring for Ø2" (Ø50.8 mm) Components, 8-32 Tap
SM1RC Support Documentation
SM1RCSlip Ring for SM1 Lens Tubes and C-Mount Extension Tubes,
8-32 Tap
+1 Qty Docs Part Number - Universal Price Available
CP36 Support Documentation
CP3630 mm Cage Plate, Ø1.2" Double Bore for SM1 and C-Mount Lens Tubes
SM1TC Support Documentation
SM1TCClamp for SM1 Lens Tubes and C-Mount Extension Tubes
SM2A21 Support Documentation
SM2A21Externally SM2-Threaded Mounting Adapter with Ø1.20" (Ø30.5 mm) Bore and 2" Outer Diameter
SM3B2 Support Documentation
SM3B2Ø2.0" Isolator to SM3 Adapter
+1 Qty Docs Part Number - Metric Price Available
C2RC/M Support Documentation
C2RC/MSlip Ring for Ø2" (Ø50.8 mm) Components, M4 Tap
SM1RC/M Support Documentation
SM1RC/MSlip Ring for SM1 Lens Tubes and C-Mount Extension Tubes,
M4 Tap