Gradient-Index Lenses - CVI Melles Griot - #1

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Gradient-index (GRIN) lenses combine refraction at the plane end surfaces with continuous refraction within the rod. Made from SELFOC®, a radial gradient-index material, GRIN lenses are easy to use and are well suited to coupling the output of a diode laser into an optical fiber.

■ Aberration correction can be achieved without complex multi­element systems or aspherics.

■ Real images are formed at the lens surface.

■ An antireflection coating reduces reflection to less than 0.5 percent per surface.

The refractive index of SELFOC® material varies parabolically as a function of radius. The index variation may be expressed as

Design Wavelength: 633, 830, 1300, or 1560 nm Gradient-Index Constant: A^1/2± 2.5% Working Distance for 0.23-Pitch Lenses:

0.21 mm at 633 nm

0.21 mm at 830 nm

0.26 mm at 1300 nm

0.26 mm at 1560 nm Working Distance for 0.29-Pitch Lenses: See graph Coating: Multilayer metal oxide Diameter: f ±0.02 mm (0.01 mm for f=1.0 mm)

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where «_r is the refractive index at a distance r from the optical axis, «o is the design index on the optical axis, and A is a positive constant.

A ray incident on the front surface follows a sinusoidal path along the rod. The period of the sinusoidal path ("pitch" of the lens) is given by

s*

nj c

M o Q_

Another important parameter is the maximum acceptance angle

V = sin^-1 (n₀Ry[A ) where R = f/2.

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