Silicon Plano-Convex Lenses

Overview

Silicon plano-convex lenses are positive focal length spherical lenses for infrared optical systems. One surface is flat and the other surface is convex, allowing the lens to focus collimated infrared radiation or collimate radiation from a point source.

Single-crystal silicon is used in NIR and MWIR optical systems because it combines useful infrared transmission, high thermal conductivity, low density, high hardness, and strong mechanical stability. It is commonly reviewed for infrared lenses, windows, substrates, and optical components in sensing, imaging, medical, defense, and industrial systems.

Why Silicon Matters for MWIR Lenses

Silicon is lighter and harder than Germanium, making it useful for compact infrared instruments and mechanically demanding assemblies. It is suitable for many 1.2-8 µm applications, but it should not be selected for 10.6 µm CO2 laser transmission optics because of absorption behavior near that wavelength.

Quick Specifications

Parameter	Guidance
Material	Single-crystal Silicon (Si)
Lens Type	Plano-convex spherical lens
Typical Transmission Range	Approximately 1.2-8.0 µm for common infrared transmission applications
Refractive Index	Approximately 3.42 in the infrared region
Diameter Range	1-500 mm depending on geometry and specification
Processing Status	Blank, rough ground, polished, uncoated, or custom coated
Coating Options	Uncoated or custom infrared AR coating, including 3-5 µm broadband AR coating

Typical Material Properties

Property	Typical Value
Density	Approximately 2.33 g/cm3
Melting Point	Approximately 1420°C
Thermal Expansion Coefficient	Approximately 4.15 × 10-6 /°C
Thermal Conductivity	Approximately 163.3 W/(m·K) at 273 K
Knoop Hardness	Approximately 1150 kg/mm2
Young's Modulus	Approximately 131 GPa

Standard Lens Options

The following silicon plano-convex lens options are useful for engineering selection. Final availability, coating, and inspection requirements should be confirmed before ordering.

Diameter	Focal Length	EFL	Coating
12.7 mm	15.0 mm, 20.0 mm, or 40.0 mm	14.3-39.4 mm	Uncoated or Ravg <1.5% @ 3-5 µm
25.4 mm	25.4 mm, 50.0 mm, 75.0 mm, 100.0 mm, 150.0 mm, or 200.0 mm	24.4-198.7 mm	Uncoated or Ravg <1.5% @ 3-5 µm
25.4 mm	500.0 mm, 750.0 mm, or 1000.0 mm	499.4-999.4 mm	Uncoated or Ravg <1.5% @ 3-5 µm

Typical Applications

• MWIR imaging systems and infrared sensors
• Signal collection and beam control in compact optical paths
• Thermal and industrial imaging systems requiring low weight and high hardness
• Medical and defense infrared assemblies after coating and environmental review
• Selected terahertz components depending on grade and design
• Laser mirror substrates when coating design and thermal load are specified

Engineering Notes

Silicon has a high refractive index, so AR coating is normally recommended for practical infrared transmission systems. For MWIR systems, coating design and angle of incidence should be reviewed early to avoid transmission loss or unwanted reflection.

For CO2 laser transmission optics, review ZnSe material guidance instead. To request a silicon PCX lens quote, send diameter, focal length, wavelength range, coating requirement, tolerance level, quantity, and drawings through the contact form.