Features

• Fiber Collimation for Single Mode Patch Cables with FC/PC Connectors
• Aligned at 405, 543, 633, 780, 1064, 1310, 1550, or 2000 nm
• Each Collimation Package is Factory Aligned
• Simplifies Free-Space Laser to Fiber Coupling
• Non-Magnetic Stainless Steel Housing

These fiber collimation packages are pre-aligned to collimate light from an FC/PC-connectorized fiber with diffraction-limited performance. Because these fiber collimators have no movable parts, they are compact and not susceptible to misalignment. Due to chromatic aberration, the effective focal length (EFL) of the aspheric lens is wavelength-dependent. As a result these collimators will only perform optimally at the design wavelength (see the Focal Length Shift tab for more information).

The aspheric lens is factory-aligned so that it is one wavelength-adjusted focal length away from the fiber tip when inserted into the collimator. In addition, the aspheric lens has an AR coating that minimizes surface reflections. For optimal collimation these packages should be used at the alignment wavelength. To obtain a high coupling efficiency, the NA of the patch cable needs to be greater than or equal to the NA of the collimator, and the diameter of the focused beam needs to be smaller than the MFD/core of the fiber. For some applications they may also be used within the AR coating range. Please refer to the AR Coating Plots Tab for more details. Please contact Technical Support for custom alignment packages.

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 Selection Guide tab or contact our technical support group.

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. Alternatively, our large selection of standard fiber patch cables can also be used.

Click to Download Reflectance Data

Chromatic Focal Shift and Collimated Beam Diameter

The aspheric lenses used in these collimation packages exhibit a wavelength-dependent focal length shift, thereby limiting their collimation performance. For example, the wavelength-dependent shift for the A240 lens, which is used in the F240 collimators, is shown below. Due to this shift, the collimated beam diameter (i.e., the diameter of the beam waist) varies for different input wavelengths (focal shift data and plots are included in the Sub Groups below). Moreover, due to diffraction, the collimated beam will spread as it propagates through space. The beam diameter at any arbitrary point can be calculated. Two examples are given below.

Example 1: Calculating the Size of the Beam Waist After the Collimation Optic is Known

Suppose you are collimating a 1310 nm light source using an F240 collimation device. From the graph to the right, we know that the beam waist will occur 8.13 mm after the collimation device. At this wavelength, the beam waist is 1.43/2 = 0.715 mm (specs included in the Sub Groups below). However, due to diffraction, the light waves will begin to spread transversely as they propagate. For a Gaussian beam propagating in free space, the spot size w(z) will vary in accordance with

Here, z is the axial distance as measured from the beam's narrowest point (i.e., the beam waist), λ is the source wavelength, and w_o is the beam radius at the waist.

Therefore, for this example, w_o = 7.15 x 10^-4 m and λ = 1310 x 10^-9 m. Substitution into the equation above allows us to determine the radius of the 1/e² irradiance contour after the wave has propagated a distance z. The results for z = 0.5 m, 1 m, and 10 m are summarized in the table below:

Example 2: Calculating the Size of the Beam Waist After the Collimation Optic is Not Known

Suppose that you are using an F240SMA-C collimator to couple 1064 nm light into 980HP fiber. The effective focal length at this wavelength is 8.08 mm (see the plot above). You'll note that the table in the sub groups below does not give the diameter of the waist after the collimation optic for this particular wavelength, so we need to determine that piece of information from the mode field diameter (MFD) of the fiber. This particular fiber has a MFD of 6.2 μm. The new waist w₀₂ is given by

Here, f is the effective focal length of the collimating optic, w₀₁ is the size of the input waist (this is just half the MFD, which is 3.1 microns in this case), λ is the input wavelength, and d is the distance the that the waist should occur from the lens (here d = f). Substitution yields

Therefore, the size of the waist after the collimation optic should be 

This value can then be substituted for w₀ in the following equation (which is discussed in Example 1)

to determine the radius of the 1/e² irradiance contour after the wave has propagatied a distance z. The results for z = 0.5 m, 1 m, and 10 m are summarized in the table below:

Theoretical Approximation of the Divergence Angle

The divergence angle listed in the specifications table above is the measured beam divergence angle when using the fiber collimator at its design wavelength with the specific fiber denoted in the specifications table footnote. This divergence angle is easy to approximate theoretically using the formula shown below as long as the light emerging from the fiber has a Gaussian intensity profile. This 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.

Example Calculation:

When the F220SMA-A collimator is used to collimate 515 nm light emerging from a 460HP fiber with a mode field diameter (D) of 3.5 µm and a focal length (f) of approximately 11.0 mm (not exact since the design wavelength is 543 nm), the divergence angle is approximately given by

θ ≈ (0.0035 mm / 11.0 mm) x (180 / 3.1416) ≈ 0.018°.

When the beam divergence angle was measured for the F220SMA-A collimator a 460HP fiber was used with 543 nm light. The result was a divergence angle of 0.018°.

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.