Webpage Feature
	These links open a window that contains additional information about the aspheric lens incorporated into each of these adjustable collimators. Here, you'll find sketches, aspheric coefficients, lens specifications, glass transmission and coefficients data, and links to the complete product drawings and catalog page documents.

Features

• Collimate Light
• Four Focal Length/Numerical Aperture Combinations
• f = 2.0 mm, NA = 0.50
• f = 4.6 mm, NA = 0.53
• f = 7.5 mm, NA = 0.30
• f = 11.0 mm, NA = 0.30
• Three AR-Coated Aspheric Lens Options
• 350 - 700 nm (400 - 600 nm for CFC-2X-A)
• 650 - 1050 nm (600 - 1050 nm for CFC-2X-B)
• 1050 - 1620 nm (1050 - 1600 nm for CFC-2X-C)
• Diffraction-Limited Performance if used with FC/PC Patch Cables
• Non-Magnetic Stainless Steel Housing
  

Thorlabs' CFC Series of Adjustable Focus FC Collimators, which consist of a spring-loaded, AR-coated aspheric lens mounted inside a stainless steel cell, are designed to collimate light exiting a fiber. For fiber-to-fiber coupling, we recommend using our PAF Series of FiberPorts or a fiber launch nanopositioning stage. The adjustable collimators featured here are available with an FC/PC receptable. Rotation of the outer barrel of the collimator leads to translation of the housed aspheric lens along the optical axis, making it possible to adjust the distance between the lens and the tip of the fiber; the optic, which is held in place with two setscrews, can be translated by a distance equal to the "Fiber-to-Lens Distance" listed in the tables below. For some models (e.g., CFC-8X-A), this distance can be as much as 2 mm.

The CFC series of collimators is comprised of four different focal length options (2.0 mm, 4.6 mm, 7.5 mm, or 11.0 mm), each of which is available with one of three antireflection coatings deposited on the aspheric lens surfaces. Please see the tables below for more information. All focal length lenses except for 11 mm provide dual FC/PC and FC/APC compatibility. In all cases, the fiber tip of the APC versions has the standard 8° wedge, leading to a 4° beam deviation from the mechanical axis of the housing.

Please note that for the 2.0 mm, 4.6 mm, and 7.5 mm focal length versions, which accept both FC/PC and FC/APC connectors, the light will not travel through the center of the apheric lens if an FC/APC connector is used. For wavefront-sensitive applications that suffer from off-axis performance characteristics of aspheres, consider using a FiberPort; with 6 degrees of freedom, the optic location can be adjusted to ensure the beam travels through the optical axis of the lens.

Also please note that the Numerical Aperture (NA) specified in the Lens Details section of the tables below is that of the aspheric lens included with the collimator, not the collimator assembly.

We recommend using adjustable 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. These cables are available with an AR-coated FC/PC or FC/APC connector. Alternatively, our large selection of standard fiber patch cables can also be used.

Theoretical Approximation of the Divergence Angle

The divergence angle listed in the specifications tables is the measured 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 an MM fiber has a non-Gaussian intensity profile.

The Divergence Angle (in degrees) is given by

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

Example:

When the CFC-2X-A collimator is used with a single mode fiber patch cable such as P1-460A-FC-2 such that D = 3.5 µm and f ≈ 2.0 mm, the divergence angle is

θ ≈ (0.0035 mm / 2.0 mm)*(180/3.1416) ≈ 0.100° or 1.75 mrad.

Theoretical Approximation of the Output Beam Diameter

The output beam diameter can be approximated from 

where λ is the wavelength of light being used, D is the mode field diameter, and f is the focal length of the collimator.

Example:

When the CFC-5X-C collimator (f = 4.6 mm) is used with the P1-SMF28E-FC-1 patch cable (MFD = 10.5 µm) and 1550 nm light, the output beam diameter is

(4)(1550 nm)[4.6 mm / (π · 10.5 µm)] = 0.865 mm

Theoretical Approximation of the Maximum Waist Distance

The maximum wast distance, which is the furthest distance from the lens the waist 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 D is the mode field diameter.

Example:

When the CFC-2X-A collimator is used with a single mode fiber patch cable such as P1-460A-FC-2 such that D = 3.5 µm, f≈ 2.0 mm, and λ = 450 nm, then the maximum waist distance is

(2 mm) + (2 (2 mm)² (450 nm) / (3.1416) (3.5 µm)) = 96 mm.

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-connectorized fiber. Each collimation package is factory aligned to provide diffraction-limited performance at one of six wavelengths: 405, 543, 633, 780, 1064, 1310, or 1550 nm. 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 spheric lens to have a wavelength dependence.
Air-Spaced Doublet, Large Beam Collimators		For large beam diameters (Ø6.6 - Ø8.5 mm), Thorlabs offers FC/PC, SMA, and FC/APC 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 conectorized fiber and provide diffraction-limited performance at the design wavelength.
Adjustable Fiber Collimators		These snap-on collimators are designed to connect onto the end of an FC/PC or FC/APC connector and contain an AR-coated aspheric lens. The distance between the aspheric lens and the tip of the FC-terminated fiber can be adjusted to compensate for focal length changes or to recollimate the beam at the wavelength and distance of interest.
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 three 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.
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.
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 reflective collimators are ideal for single-mode fiber.
Pigtailed Collimators		Our pigtailed collimators come with one meter of either single mode or multimode fiber, have the fiber and AR-coated aspheric lens rigidly potted inside the stainless steel housing, and are collimated at one of six wavelengths: 532, 830, 1030, 1064, 1310, 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.
GRIN Fiber Collimators		Thorlabs offers gradient index (GRIN) fiber collimators that are aligned for either 980, 1064, 1310, or 1550 nm and have either FC connectorized, APC connectorized, 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.