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.
Four Focal Length Options: 2.0 mm, 4.6 mm, 7.5 mm, and 11.0 mm
Three AR-Coated Aspheric Lens Options
350 - 700 nm
650 - 1050 nm (600 - 1050 nm for CFC-2X-B)
1050 - 1620 nm (1050 - 1700 nm for CFC-2X-C)
Diffraction-Limited Performance if used with FC/PC Patch Cables
Non-Magnetic Stainless Steel Housing
Thorlabs' 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 FiberPorts or a fiber launch nanopositioning stage. The adjustable collimators featured here are available with an FC/PC receptacle. 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. Once the desired position is reached, the adjustment can be locked into place using two 0-80 setscrews and the included 0.7 mm hex key. The optic can be translated by a distance equal to the "Fiber-to-Lens Distance" listed in the tables below.
These collimators are 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. Each collimator can be made compatible with our SM1 (1.035"-40) threading by mounting it in an AD9.5F collimator mounting adapter.
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 aspheric 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 incorporated into the collimator, not the entire 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 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 an MM 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).
When the CFC-2X-A collimator is used with a single mode fiber patch cable such as our former item P1-460A-FC-2 such that MFD = 3.3 µm and f ≈ 2.0 mm, the divergence angle is
θ ≈ (0.0033 mm / 2.0 mm)*(180/3.1416) ≈ 0.095° or 1.66 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, MFD is the mode field diameter, and f is the focal length of the collimator.
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)] = 0.87 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.
When the CFC-2X-A collimator is used with a single mode fiber patch cable such as our former item P1-460A-FC-2 such that MFD = 3.3 µm, f ≈ 2.0 mm, and λ = 488 nm, then the maximum waist distance is
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.
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-terminated fiber and provide diffraction-limited performance at the design wavelength.
These 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.
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.
Thorlabs' Large-Beam Fiber Collimators are designed with an effective focal length (EFL) of 40 mm or 80 mm over three different wavelength ranges and are available with FC/PC or FC/APC connectors. A four-element, air-spaced lens design produces a superior beam quality (M2 close to 1) and less wavefront error when compared to aspheric lens collimators. As a result, these collimators are very flexible; they can be used as free-space collimator or coupler. They may also be used over a long distance in pairs, which allows the free-space beam to be manipulated prior to entering the second collimator and may be useful in long-distance communications applications.
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.
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.
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.
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.
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.
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.