Comparison of silicon lenses and germanium lenses
Silicon lens: suitable for NIR and MIR, high hardness, good thermal stability, low cost.
Germanium lens: suitable for MIR and FIR, high refractive index, easy to process, but high cost, poor thermal stability.

Applications of monocrystalline silicon lenses
1. Infrared optics: monocrystalline silicon is typically used as a substrate for 3-5 μm mid-wave infrared optics windows and optical filters.
2. Laser mirrors: monocrystalline silicon is also a common material for laser mirror substrates.
3. Superstructured lenses: superstructured lenses based on monocrystalline silicon octagonal nanopillars have promising applications in the visible wavelength band, especially in optical sensors.