• Graded-Index Lenses for Fiber Coupling and Collimation
• Uncoated
• Small, Low-Cost Design is Ideal for Telecom Applications

Thorlabs’ GRIN2906 graded-index (GRIN) lens is designed for use at 630 nm. GRIN lenses are typically used in fiber-based passive and active components to couple laser light from one fiber through a free space optical system and back into another fiber. This lens can also be used for coupling the output of laser diodes into fibers, focusing laser light onto a detector, or collimating laser light.

GRIN lenses' major advantage over aspheric lenses is their lower cost and ease of handling due to the sleeve and ferrule (available separately). Additionally they 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 (index multiplied by distance) are the same due to the radially varying index of refraction. This is in contrast with a traditional spherical or aspheric lens.

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 (ie, 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). This GRIN lens features pitches of 0.23 and 0.29, which are just short of focus and just past focus, respectively.

• Transmittance: >89%, 380 – 2000 nm
• Polarization Preservation: 0.99
• Operating Temperature: <350 °C
• Pitch: 0.29
• Facet Angle: 0°
• Design Wavelength: 630 nm
• Effective Focal Length: 1.90 mm
• Working Distance: 1.411 mm
• Index: 1.6073
• NA: 0.46
• Gradient Constant: 0.339 mm^-1
• Diameter: Ø1.8 mm