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KAD11F Kinematic Tip/Tilt Adapter Used to Mount a Fiber Collimator in
an LM1XY Translation Mount

Features

• Fiber Collimators with FC/APC Connectors (2.2 mm Wide Key) for Single Mode Patch Cables
• Aligned at Wavelengths from 405 nm to 4.55 µm (See Table to the Right)
• Collimated Beam Diameters from 0.63 mm to 4.05 mm Depending on Wavelength
• Each Collimation Package is Factory Aligned
• Simplifies Fiber-Coupled Detection Systems
• Non-Magnetic Stainless Steel Housing
• Compatible with Narrow and Wide Key FC/APC Connectors
• Custom Options, Including Custom Alignment Wavelengths, Available by Contacting Tech Support

These fiber collimation packages are pre-aligned to collimate light from an FC/APC-terminated fiber with diffraction-limited performance. Because these fiber collimators have no movable parts, they are compact and easy to integrate into an existing setup. Due to chromatic aberration, the effective focal length (EFL) of the aspheric lens is wavelength dependent. The design wavelength indicates the wavelength of ideal beam divergence (see the Divergence Plots and Calculations tabs for more information). Collimation packages at select design wavelengths are available with different collimated beam diameters. Select a wavelength from the quick links table to the right for details.

The aspheric lens is factory aligned for collimation at the design wavelength when connected to its specified single mode fiber patch cable. In addition, the aspheric lens has an AR coating on both sides that minimizes surface reflections (see the AR Coating Plots tab). For some applications they may also be used at other wavelengths within the AR coating range; please refer to the theoretical divergence plot for each collimator to determine if it is appropriate for your application. The operating temperature range for these collimators is -40 °C to 93 °C. Please note that these collimation packages are not vacuum compatible. Collimation packages with custom alignment wavelengths, operating temperature ranges, or vacuum compatibility are available by contacting Tech Support.

These fiber collimators are intended for use with single mode fiber patch cables. For improved performance, we recommend using these collimators with our AR-coated single mode fiber optic patch cables. These cables feature an antireflective coating on one fiber end for increased transmission and improved return loss at the fiber-to-free-space interface. Please note performance specifications are guaranteed only when used with single mode fiber.

To mount these fiber collimation packages, we recommend using our collimator mounting adapters, including our kinematic collimator mounting adapters that provide pitch and yaw adjustment. In addition to Ø1/2" and Ø1" unthreaded versions, options are available with external SM05 (0.535"-40), RMS (0.800"-36), or SM1 (1.035"-40) threading. The collimation packages with external M12 x 0.5 threading can be mounted directly into our cage plate CP1M12(/M) to be integrated into our 30 mm cage systems.

Mid-IR Collimators
For our collimators with an alignment wavelength of 3.45 µm and 4.55 µm, we recommend using our angle-polished fluoride fiber patch cables; these collimators include a tightly toleranced ceramic sleeve to protect the fluoride fiber tip during insertion and improve pointing stability. Although these collimators are factory aligned for a specific wavelength, they have low divergence angles over a broad range of wavelengths. Therefore, they may be used at other wavelengths within the AR coating range. Please refer to the theoretical divergence plot for each collimator to determine if it is appropriate for your application.

Alternatives
We also offer a line of adjustable collimation packages called FiberPorts that are well suited for a wide range of wavelengths. These are ideal solutions for adjustable, compact fiber couplers. For other collimation and coupling options, please see our Collimator Guide tab or contact Tech Support.

• See the tables below for the designated coating ranges for specific collimators.

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Divergence Angle Comparison

The divergence angle can be estimated using the formula shown to the right, given that the light emerging from the fiber has a Gaussian intensity profile. This formula works well for single mode fibers but will underestimate the divergence angle for multimode fibers where the light emerging from the fiber has a non-Gaussian intensity profile.

Simulations of the theoretical divergence when using one of our standard collimators at wavelengths other than the design wavelength are shown in the graphs below. For example, if you need to collimate 700 nm light from a fiber into a ~1.5 mm diameter beam, the F240APC-780 collimator (represented by the '-780' line in the F240 graph below) can be used but will provide a higher divergence than at its design wavelength of 780 nm. Individual theoretical divergence plots and raw data are also available below for each collimator. Please contact Tech Support to request a collimator aligned at a custom wavelength.

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Theoretical Approximation of the Divergence Angle

The beam diameter as a function of propagation distance was simulated for each of our collimators at the design wavelength, assuming input from the design fiber and a Gaussian intensity profile. The design wavelength and fiber are specified in the caption for each graph.

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At 405 nm with S405-XP Fiber

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At 532 nm with 460HP Fiber

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At 543 nm with 460HP Fiber

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At 635 nm with SM600 Fiber

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At 780 nm with 780HP Fiber

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At 850 nm with 780HP Fiber

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At 980 nm with SM980-5.8-125 Fiber

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At 1064 nm with SM980-5.8-125 Fiber

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At 1310 nm with SMF-28-J9 Fiber

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At 1550 nm with SMF-28-J9 Fiber

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At 2000 nm with SM2000 Fiber

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At 3.45 µm with ZrF₄ Fiber

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At 4.55 µm with InF₃ Fiber

Theoretical Approximation of the Divergence Angle

The full-angle beam divergence listed in the specifications tables is the theoretically-calculated value associated with the fiber collimator. This divergence angle is easy to approximate theoretically using the formula below as long as the light emerging from the fiber has a Gaussian intensity profile. Consequently, the formula works well for single mode fibers, but it will underestimate the divergence angle for multimode (MM) fibers since the light emerging from a multimode fiber has a non-Gaussian intensity profile.

The Full Divergence Angle (in degrees) is given by

where MFD is the mode field diameter and f is the focal length of the collimator. (Note: MFD and f must have the same units in this equation).

Example:

When the F220FC-A collimator (f ≈ 11.0 mm; not exact since the design wavelength is 543 nm) is used to collimate 515 nm light emerging from a 460HP fiber (MFD = 3.5 µm), the divergence angle is approximately given by

θ ≈ (0.0035 mm / 11.0 mm) x (180 / pi) = 0.018°.

When the beam divergence angle was measured for the F220FC-A collimator, a 460HP fiber was used with 543 nm light. The result was a divergence angle of 0.018°.

Theoretical Approximation of the Output Beam Diameter

The output beam diameter can be approximated from

where λ is the wavelength of light being used, MFD is the mode field diameter, and f is the focal length of the collimator. (Note: MFD and f must have the same units in this equation).

Example:

When the F240FC-1550 collimator (f = 8.18 mm) is used with the P1-SMF28E-FC-1 patch cable (MFD = 10.4 µm) and 1550 nm light, the output beam diameter is

d ≈ (4)(0.00155 mm)[8.18 mm / (pi · 0.0104 mm)] = 1.55 mm.

Theoretical Approximation of the Maximum Waist Distance

The maximum waist distance, which is the furthest distance from the lens the waist can be located in order to maintain collimation, may be approximated by

where f is the focal length of the collimator, λ is the wavelength of light used, and MFD is the mode field diameter. (Note: MFD and f must have the same units in this equation).

Example:

When the F220FC-532 collimator (f = 10.9 mm) is used with the P1-460B-FC-1 patch cable (MFD ≈ 4.0 µm; calculated approximate value) and 532 nm light, then the maximum waist distance is approximately

z_max ≈ 10.9 mm + [2 · (10.9 mm)² · 0.000532 mm] / [pi · (0.004 mm)²] = 2526 mm.

Insights into Best Lab Practices

Scroll down to read about some practices we follow when setting up lab equipment.

• Align Fiber Collimators to Create Free Space Between Fibers
• Fiber Collimators: Tip for Mounting with Adapters

Click here for more insights into lab practices and equipment.

Align Fiber Collimators to Create Free Space Between Fibers

Two collimators, inserted into a fiber optic setup, provide free-space access to the beam. The first collimator accepts the highly diverging light from the first fiber and outputs a free-space beam, which propagates with an approximately constant diameter to the second collimator. The second collimator accepts the free-space beam and couples that light into the second fiber. Some collimation packages, including the pair used in this demonstration, are designed for use with optical fibers and mate directly to fiber connectors.

Ideally, 100% of the light emitted by the first fiber would be coupled into the second fiber, but some light will always be lost due to reflections, scattering, absorption, and misalignment. Misalignment, typically the largest source of loss, can be minimized using the alignment and stabilization techniques described in this video.

In this demonstration, the first fiber is single mode. The optical power incident on the second collimator, as well as the power output by the second fiber, are measured. When the second fiber is multimode with a 50 µm diameter core, alignment resulted in 91% of the power incident on the second collimator being measured at the fiber output. This value was 86% when the second fiber is single mode. Some differences in collimator designs, and their effects on the characteristics of the collimated beams, are also discussed.

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.

Date of Last Edit: April 21, 2021

Fiber Collimators: Tip for Mounting with Adapters

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Figure 1: The components shown above are joined using threaded interfaces. Since unscrewing the fiber connector could unintentionally loosen connections between the other components, Thorlabs suggests applying epoxy to the other two interfaces to immobilize them.

Fiber collimators are often used to introduce light into an optical setup from a fiber coupled source. Thorlabs offers a variety of fiber collimator packages, some only provide a smooth barrel (like the triplet collimators) and others have a metric thread at the end of the barrel (like the asphere collimators).

For both packages, Thorlabs typically suggests the use of an adapter with a nylon tipped set screw that holds the barrel against a two line contact.

Adapters for the external thread are available (AD1109F) that allow the user to thread the fiber collimator into a mount.

However, the use of these adapters results in a stack up of threaded interfaces (threaded fiber connector, threaded collimator, and threaded adapter). As a result, it is possible that unscrewing the fiber connector could inadvertently loosen another thread interface and create an unknown source of instability in the setup.

For this reason, Thorlabs suggests epoxying the threaded fiber collimators into the threaded mounts if that mounting mechanism is preferred.

Figure 1 indicates the assembly order and places to apply the epoxy.

Date of Last Edit: Dec. 4, 2019

Fiber Collimator Selection Guide

Click on the collimator type or photo to view more information about each type of collimator.

Type		Description
Fixed FC, APC, or SMA Fiber Collimators		These fiber collimation packages are pre-aligned to collimate light from an FC/PC-, FC/APC-, or SMA-terminated fiber. Each collimation package is factory aligned to provide diffraction-limited performance for wavelengths ranging from 405 nm to 4.55 µm. Although it is possible to use the collimator at detuned wavelengths, they will only perform optimally at the design wavelength due to chromatic aberration, which causes the effective focal length of the aspheric lens to have a wavelength dependence.
Air-Spaced Doublet, Large Beam Collimators		For large beam diameters (Ø5.3 - Ø8.5 mm), Thorlabs offers FC/APC, FC/PC, and SMA air-spaced doublet collimators. These collimation packages are pre-aligned at the factory to collimate a laser beam propagating from the tip of an FC or SMA-terminated fiber and provide diffraction-limited performance at the design wavelength.
Triplet Collimators		Thorlabs' High Quality Triplet Fiber Collimation packages use air-spaced triplet lenses that offer superior beam quality performance when compared to aspheric lens collimators. The benefits of the low-aberration triplet design include an M2 term closer to 1 (Gaussian), less divergence, and less wavefront error.
Achromatic Collimators for Multimode Fiber		Thorlabs' High-NA Achromatic Collimators pair a meniscus lens with an achromatic doublet for high performance across the visible to near-infrared spectrum with low spherical aberration. Designed for use with high-NA multimode fiber, these collimators are ideal for Optogenetics and Fiber Photometry applications.
Reflective Collimators		Thorlabs' metallic-coated Reflective Collimators are based on a 90° off-axis parabolic mirror. Mirrors, unlike lenses, have a focal length that remains constant over a broad wavelength range. Due to this intrinsic property, a parabolic mirror collimator does not need to be adjusted to accommodate various wavelengths of light, making them ideal for use with polychromatic light. Our fixed reflective collimators are recommended for collimating single and multimode fiber and coupling into multimode fiber. These collimators are available with UV-enhanced aluminum or protected silver reflective coatings and with FC/PC, FC/APC, or SMA connector compatibility.
Compact Reflective Collimators		Thorlabs' Compact Reflective Collimators incorporate a 90° off-axis parabolic mirror with a protected silver coating. Because the focal length is independent of wavelength for an off-axis parabolic mirror, they are ideal for use with polychromatic light. Our fixed reflective collimators are recommended for collimating single and multimode fiber and coupling into multimode fiber. These collimators are directly compatible with our 16 mm cage system. They are available with FC/PC, FC/APC, or SMA connector inputs.
Adjustable Reflective Collimators		Thorlabs' Adjustable Focus Reflective Collimators are based on a 90° off-axis parabolic (OAP) mirror with a protected silver coating. The adjustable fiber-to-OAP distance, combined with the OAP having a constant focal length across wavelengths, makes these collimators ideal for optimizing collimation or coupling of polychromatic light with single mode or multimode fiber. These adjustable collimators have a 15 mm reflected focal length and are available with FC/PC, FC/APC, or SMA connectors.
FiberPorts		These compact, ultra-stable FiberPort micropositioners provide an easy-to-use, stable platform for coupling light into and out of FC/PC, FC/APC, or SMA terminated optical fibers. It can be used with single mode, multimode, or PM fibers and can be mounted onto a post, stage, platform, or laser. The built-in aspheric or achromatic lens is available with five different AR coatings and has five degrees of alignment adjustment (3 translational and 2 pitch). The compact size and long-term alignment stability make the FiberPort an ideal solution for fiber coupling, collimation, or incorporation into OEM systems.
Adjustable Fiber Collimators		These collimators are designed to connect onto the end of an FC/PC, FC/APC, or SMA connector and contain an AR-coated aspheric lens. The distance between the aspheric lens and the tip of the fiber can be adjusted to compensate for focal length changes or to recollimate the beam at the wavelength and distance of interest.
Achromatic Fiber Collimators with Adjustable Focus		Thorlabs' Achromatic Fiber Collimators with Adjustable Focus are designed with an effective focal length (EFL) of 20 mm, 40 mm, or 80 mm, have optical elements broadband AR coated for one of three wavelength ranges, and are available with FC/PC, FC/APC, or SMA905 connectors. A four-element, air-spaced lens design produces superior beam quality (M2 close to 1) and less wavefront error when compared to aspheric lens collimators. These collimators can be used for free-space coupling into a fiber, collimation of output from a fiber, or in pairs for collimator-to-collimator coupling over long distances, which allows the beam to be manipulated prior to entering the second collimator.
Zoom Fiber Collimators		These collimators provide a variable focal length between 6 and 18 mm, while maintaining the collimation of the beam. As a result, the size of the beam can be changed without altering the collimation. This universal device saves time previously spent searching for the best suited fixed fiber collimator and has a very broad range of applications. They are offered with FC/PC, FC/APC, or SMA905 connectors with three different antireflection wavelength ranges to choose from.
Single Mode Pigtailed Collimators		Our single mode pigtailed collimators come with one meter of fiber, consist of an AR-coated aspheric lens pre-aligned with respect to a fiber, and are collimated at one of eight wavelengths: 532 nm, 633 nm, 780 nm, 850 nm, 1030 nm, 1064 nm, 1310 nm, or 1550 nm. Although it is possible to use the collimator at any wavelength within the coating range, the coupling loss will increase as the wavelength is detuned from the design wavelength.
Polarization Maintaining Pigtailed Collimators		Our polarization maintaining pigtailed collimators come with one meter of fiber, consist of an AR-coated aspheric lens pre-aligned with respect to a fiber, and are collimated at one of five wavelengths: 633 nm, 780 nm, 980 nm, 1064 nm, or 1550 nm. Custom wavelengths and connectors are available as well. A line is engraved along the outside of the housing that is parallel to the fast axis. As such, it can be used as a reference when polarized light is launched accordingly. Although it is possible to use the collimator at any wavelength within the coating range, the coupling loss will increase as the wavelength is detuned from the design wavelength.
GRIN Fiber Collimators		Thorlabs offers gradient index (GRIN) fiber collimators that are aligned at a variety of wavelengths from 630 to 1550 nm and have either FC terminated, APC terminated, or unterminated fibers. Our GRIN collimators feature a Ø1.8 mm clear aperture, are AR-coated to ensure low back reflection into the fiber, and are coupled to standard single mode or graded-index multimode fibers.
GRIN Lenses		These graded-index (GRIN) lenses are AR coated for applications at 630, 830, 1060, 1300, or 1560 nm that require light to propagate through one fiber, then through a free-space optical system, and finally back into another fiber. They are also useful for coupling light from laser diodes into fibers, coupling the output of a fiber into a detector, or collimating laser light. Our GRIN lenses are designed to be used with our Pigtailed Glass Ferrules and GRIN/Ferrule sleeves.