Features

• Provides Collimation and Focusing of Fiber-Coupled Light
• Designed for Easy Integration with Pigtailed Ferrules
• 1300 nm and 1560 nm Versions are AR Coated
• 8° or 0° Face Angle
• Ideal for Telecom Applications

Thorlabs' family of graded-index (GRIN) lenses has been specially designed to be paired with our bare or connectorized pigtailed ferrules. In contrast to our pigtailed aspheric lenses and jacketed GRIN collimators, this product family allows the combination of GRIN lens and optionally connectorized pigtailed ferrule to be individually chosen, satisfying a wide range of experimental requirements. See the image to the right for an example of an assembled device, or use the Selection Guide below to choose compatible lens and pigtailed ferrule combinations for your specific application.

GRIN lenses are generally used to collimate or reimage the output of a fiber. Typical applications include coupling the output of diode lasers into fibers, focusing laser light onto a detector, or collimating laser light. The lenses listed here are designed for a central wavelength of 630, 830, 1060, 1300, or 1560 nm, and are available with either an 8° or 0° face angle. The 8° versions maximize the return loss by back reflecting the incident light at a non-normal angle and are recommended for building collimators. In contrast, the 0° versions are easier to align but are only recommended for general fiber-to-fiber coupling. The 1300 and 1560 nm lenses additionally feature an AR coating that reduces reflections at the interfaces to below 0.2% at the specified wavelengths, minimizing back reflections and insertion losses. Our line of pigtailed ferrules provides an 8° or 0° face angle that is designed to match the GRIN lenses.

GRIN lenses do not require an air gap to function since the operation of the lens is due to varying indices in the lens itself, rather than the difference in indices between the air and lens. Additionally, in a GRIN lens, all optical paths (refractive index multiplied by distance) are the same due to the radially varying refractive index, in contrast to a spherical or aspheric lens. For information on how to calculate the refractive index as a function of radius, please see the Specs tab.

A ray incident on the front surface of a GRIN lens follows a sinusoidal path along the rod. The "pitch" of the lens is the fraction of a full sinusoidal period that the ray traverses in the lens (i.e., a lens with a pitch of 0.25 has a length equal to 1/4 of a sine wave, which would collimate a point source at the surface of the lens). Our GRIN lenses feature pitches of 0.23 and 0.29, which are just short of focus and just past focus, respectively. For ray diagrams detailing how lenses with different pitches are used, please see the Ray Diagrams tab.

The 0.29 pitch lenses include 0° end faces.

The 0.23 pitch lenses include an 8° angled facet to minimize back reflection and compensate for the angular beam deviation from angled fiber ferrules.

• The "pitch" of the lens is the fraction of a full sinusoidal period that the ray traverses in the lens (i.e., a lens with a pitch of 0.25 has a length equal to 1/4 of a sine wave, which would collimate a point source located at the surface of the lens).
• Tolerance: +0.005/-0.010
• These lenses are AR coated for the 1250 - 1650 nm spectral range and offerR_avg < 0.2% over this range.

Index as a Function of Radius
The index as a function of radius, as shown in the diagram to the right, may be calculated with the equation:

where n₁ is the index of refraction on the optical axis, √A is the gradient constant, and r is the radial position (ranging from -D/2 to +D/2, where D is the diameter).

Relating Pitch and Lens Length
The pitch and length of a GRIN lens may be related using the following equation:

where P is the pitch of the lens and Z is the length of the lens.

The following ray diagrams are results from ZEMAX and are designed to show the uses of Thorlabs' GRIN lenses for various fiber coupling and collimating applications. For more details on the suitablilty for a GRIN lens to a particular application, please contact Technical Support.

GRIN Lenses with Pitch = 0.23

Coupling Collimated Light into a Fiber

Click to Enlarge

Collimating a Fiber with 0.14 Numerical Aperture

Click to Enlarge

1:1 Coupling from Fiber-to-Fiber

Click to Enlarge

Off-Axis Performance for Fiber Coupling

Click to Enlarge

GRIN Lenses with Pitch = 0.29

1:1 Coupling from Fiber-to-Fiber

Click to Enlarge

Theoretical Spot Size Resulting from the 1:1 Coupling Shown to the Left

Click to Enlarge

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.