• Ø8 mm Positive Achromatic Doublet
• Focal Lengths: 20.0 mm
• Wavelength-Dependent Focal Length Shift Data for Each Doublet
• Surface Quality: 40/20 Scratch/Dig

Thorlabs' cemented Achromatic Doublet, which is designed for use in the near near IR spectral region (650 - 1050 nm), is computer optimized at infinite conjugate ratios. With design wavelengths at 706.5 nm, 855.0 nm, and 1015 nm, this doublet is useful for controlling chromatic aberration; it is frequently used to achieve a diffraction-limited spot when using a monochromatic source like a laser.

For best performance when collimating a point source with a positive focal length doublet, generally the first air-to-glass interface should have the greater radius of curvature (i.e., the flatter surface). Conversely, when focusing a collimated beam, the air to glass interface with the shorter radius of curvature (i.e., the more steeply curved surface) should face the incoming beam. When using a negative focal length achromatic doublet to diverge a collimated beam, the concave air-to-glass interface should face the collimated source.

• Design Wavelengths: 706.5 nm, 855 nm, and 1015 nm
• Diameter Tolerance: +0.00/-0.10 mm
• Focal Length Tolerance: ±1%
• Surface Quality: 40/20 Scratch/Dig
• Spherical Surface Power: 3?/2
• Spherical Surface Irregularity: ?/4
• Centration: =3 arcmin
• Clear Aperture: >90% of Diameter
• B Coating Range: R_avg < 0.5% (650 - 1050 nm)
• Damage Threshold: 5.0 J/cm² (810 nm, 10 ns pulse, 10 Hz, Ø0.155 mm)
• Operating Temperature: -40 °C to 85 °C
• Diameter: 8 mm
• f: 20 mm
• f_b: 18.2 mm
• r₁: 13.53 mm
• r₂: -10.59 mm
• r₃: -47.75 mm
• t_c1: 2.3 mm
• t_c2: 1.3 mm
• t_e: 2.8 mm
• Materials: N-LAK22/N-SF6HT
• Recommended Lens Mounting Option: LMRA8 with a LMR05