Sapphire

Single-crystal sapphire is an exceptional material for optical applications, particularly in demanding environments involving high temperatures, intense radiation, or harsh conditions. Its wide transparency range, exceptional hardness, chemical inertness, and thermal stability make it invaluable for UV optics, laser optics, infrared optics, and protective coatings.

However, its birefringence, high hardness, and the complexity of crystal growth can pose challenges in certain applications and manufacturing processes.

This technical summary provides an overview of the key characteristics and applications of Sapphire in optical systems. For more information see the Product Data Sheet

Crystal Structure and Properties

Sapphire is a crystalline form of aluminum oxide (Al2O3) with a rhombohedral crystal structure.

It has an extremely wide bandgap of 8.7 eV, making it transparent from the deep ultraviolet (UV) to the mid-infrared (IR) region, with a broad transmission range of 0.15 μm to 5.5 μm.

Sapphire exhibits exceptional hardness (Mohs hardness of 9) and chemical inertness, making it highly resistant to scratches, abrasion, and harsh environments.

It has a high melting point of 2,050°C and excellent thermal conductivity, allowing it to withstand high temperatures and intense radiation.

Sapphire has a relatively high refractive index of 1.77 in the visible range, which is useful for optical components requiring high refractive index materials.

Optical Applications

UV Optics: Sapphire is widely used for optics in the UV region, such as lenses, windows, and filters, due to its wide bandgap and excellent UV transparency.

Laser Optics: Sapphire is commonly employed in high-power laser systems as a material for laser rods, windows, and other optical components, owing to its exceptional thermal and mechanical properties.

Infrared Optics: Sapphire is utilized for infrared optics, such as lenses, windows, and domes, in applications where high temperatures, intense radiation, or harsh environments are encountered.

Protective Coatings: Sapphire is used as a protective coating material for optical components, such as camera lenses and watch crystals, due to its exceptional hardness and scratch resistance.

Fabrication and Processing

Single-crystal sapphire is typically grown using techniques like the Czochralski process, heat exchanger method (HEM), or edge-defined film-fed growth (EFG) method. - Sapphire can be polished to obtain high-quality optical surfaces with extremely low surface roughness.

Challenges and Limitations

The fabrication of high-quality, large-diameter sapphire crystals can be challenging and expensive due to the high temperatures and specialized techniques required.

Sapphire is a birefringent material, meaning it exhibits double refraction, which can be a limitation in certain optical applications where polarization effects need to be minimized.

The high hardness of sapphire can make machining and processing more difficult compared to softer optical materials.

Sapphire

Crystal Structure and Properties

Optical Applications

Fabrication and Processing

Challenges and Limitations

This website uses cookies.