Precision Optical Plano Concave Lenses for Beam Expansion and Light Divergence

1. Material & Fabrication

   • Substrates: Optical glass (N-BK7, SF11), Fused Silica (UV grade), CaF₂ (deep UV), ZnSe/Ge (IR)

   • Precision Standards: λ/4 surface accuracy, ±0.01mm thickness tolerance, <3 arcmin centration error

   • Coatings: Broadband/V-Lambda AR options (>99.5% transmission)

2. Key Optical Properties

   • Focal Length: Negative (typically -10mm to -1000mm)

   • Surface Quality: 20-10 scratch-dig specification

   • Wavefront Distortion: < λ/2 @ 632.8nm

   • Geometric Feature: Flat (plano) surface + inward-curving (concave) surface

3. Primary Functions

   • Beam Expansion: Diverges collimated input to widen laser diameter (e.g., pre-collimation in Galilean telescopes)

   • Light Divergence: Creates controlled spreading for uniform illumination

   • Focal Length Reduction: Compensates for convergence in imaging systems

   • Aberration Correction: Counters spherical distortion in multi-lens assemblies

4. Critical Applications

   • Laser Systems: Beam shaping in Nd:YAG/CO₂ lasers, fiber collimators, and interferometers

   • Imaging Optics: Field flattening for microscopes/telescopes, eyepiece correction

   • Sensing & LiDAR: Divergence control in rangefinders and 3D scanners

   • Illumination: Uniform light distribution in medical/scientific devices

   • Metrology: Wavefront manipulation in interferometric testing