Sapphire Windows

Sapphire Windows, featuring reliable mechanical/thermal/chemical robustness, large dielectric constants, and broad optical transmission from 150-5500 nm, are excellent as both optical windows and protective windows in application contexts of more stringent requirements and extreme conditions.

Sapphires' unmatched mechanical toughness and hardness are what make them stand out the most. Sapphire has a Mohs hardness of 9, making it the third hardest substance ranked after diamond and moissanite). In truth, sapphire windows can just sometimes be injured with substances other than sapphire itself due to their high resistance to scratches and abrasions. This indicates that sapphire windows are ideal for applications that will encounter splattering abrasive particles, such as drilling viewport windows, protective laser processing windows, and gun sights, as sapphire windows can ensure clear optical apertures and maintain lucid sights even under attacks from sand or grit.

Sapphire windows can sustain tremendous pressure and be formed into much thinner pieces without cracking than their dielectric equivalents because of the solid internal covalent bonding of sapphire. For instance, sapphire windows are often chosen in deepwater and navigation scenarios.

Sapphire is also heat-resistant, with a maximum working temperature of 1600°C and a maximum melting temperature of 2000°C. In comparison to other optical materials, sapphire windows have a distinct advantage in tolerating high-temperature conditions due to their high thermal conductivity. Sapphire windows are thus excellent choices for combustion chambers, high-temperature plasma chambers, etc.

Sapphire windows are resistant to most acids and alkalis, except hot caustic salts. Sapphire performs better than other materials in enduring corrosive substances and erosive environments, enabling greater use of sapphire windows in chemical, pharmaceutical, and medical facilities.

Furthermore, sapphire windows have a broad spectral transmission range of 150 nm to 5500 nm. The transmission spectra of N-BK7 and UV Fused Silica, the two most common optical glass materials, are 350 nm-2200 nm and 200 nm-2200 nm. However, sapphire outperforms N-BK7 with superior UV functions and a wider IR transmission and UV UV-fused silica with less IR absorption. Sapphire windows could be utilized in multi-spectrum optical tasks.

Shalom EO offers various kinds of Sapphire Windows. This is a list of a complete portfolio of our off-the-shelf sapphire windows.  These stocked sapphire windows are uncoated, of circular or square shapes, with a wide selection of available diameters (or side lengths) up to 150mm and C-cut orientation. Most of the sapphire windows in our inventories are manufactured with 60/40 S/D surface qualities and 2λ flatness, however, advanced versions with 40/20 S/D and λ/4 flatness are also procurable as stocks. The sapphire windows are manufactured using KY (Kyropoulos) -grown single crystal sapphire, endowing the material sapphires with high homogeneities, low inclusions, few striae, and large-dimension capabilities.

Hangzhou Shalom EO manufactures and supplies sapphire windows, our engineers are willing to arrange and supervise the entire sapphire window production procedure according to your needs. Our sapphire windows feature exceptional hardness, temperature endurance, environmental durability, and optical transmission. Each stage of production including sapphire growth, drilling, cutting, grinding, polishing, and cleaning is carried out using forward techniques and designed equipment, under stringent regulations, to ensure the superior properties of our sapphire widows. Before shipment, all the products will go through an in-house inspection. With our proficient production line, we are capable of delivering high-precision sapphire windows as well as volume production. 

Besides the stocked versions, Shalom EO also supplies custom sapphire windows. 

The sapphire chosen to make sapphire windows is Alpha Sapphire, manufactured in labs and factories using particular artificial methods. The produced sapphire or sapphire glass is colorless, has higher Al2O3 purities, excludes water, and has more organized, predictable micro-structures than natural sapphire, making it better equipped to meet industrial and optical-grade requirements. Keep in mind that all sapphires are single crystals, and during the growth and cutting processes, sub-grains are avoided all the time.

Alpha-Sapphire has a hexagonal structure. The lattice constant is a=b=4.758A, c=12.991A. Alpha-sapphire constitutes hexagonal-closest piled oxide floors, and the 3/2 gaps of the octahedron are filled with Al3+ ions., six floors of Al2O3 unit cells are arranged in ARAB manners. 

Orientations of Sapphire:

As shown in the diagram below, sapphire windows often have the following orientations: "a," "c," "n," and "m. Sapphire is birefringent to a subtle extent and so in critical optical situations, the windows should be specified as 'zero degrees', or 'c-cut'. C-cut sapphire has the birefringence effect removed since it is cut in a direction perpendicular to the c-axis, which is parallel to the sapphire optical axis. When it comes to protecting and packaging usages such as the sight glass of wristwatches, A-cut sapphire is often utilized, which is cut in a direction perpendicular to the A-axis, containing exceptional mechanical hardness and scratch resistance. If unspecified, the component will be of a 'random' cut, but it is worth noting that this is, for the most part, 60° to the optic axis as this is the 'softest' direction for the sawing. Random-cut sapphire is common because of lower costs and is acceptable if there are no stringent requirements about optical or mechanical qualities. However, as mentioned above, because the behavior of sapphire varies depending on orientations, random orientation might be subject to spontaneous variations of strength and other properties in the final product.

Orientation Index:

C-plane (0001) = Z-cut 

A-plane (11-20) = Y-cut 

M-Plane (10-10) = X-cut 

R-Plane (10-10)

The Lattice Structure of Sapphire and Common Sapphire Crystal Orientations

The mechanical properties of single-crystal sapphires are relevant to their densities, the greater the densities, the better the mechanical properties. Single crystal sapphires with 100% Al2O3 composition are supposed to have theoretical densities of 3.68g/cm3. Under such presumption, the mechanical properties of sapphire are the best. Its anti-compression strength is between 1.9-24 GPa. The Young’s Modulus of sapphire is 380 Gpa, which is about twice the magnitude of iron’s 200 GPa. 

The enormous hardness is another important feature of sapphire, its Mohs hardness is 9, ranking right after diamond, indicating that optical components crafted using sapphire are resistant to scratch and wear. The hardness of sapphire is also proportionate in a positive manner to the purities of sapphire.

Thermal Properties of Sapphire:

Thermal properties in main include thermal conduction coefficients, thermal diffusion coefficients, specific heat, and thermal expansion coefficients. The thermal properties of sapphire relate to the purities of sapphire. In common circumstances, the higher the purities, the higher the thermal conduction coefficients and thermal diffusion coefficients, while there is no regular pattern between Al2O3 purities and the magnitude of thermal expansion coefficients. In fact, manufacturers seem unable to agree on the thermal expansion coefficient of sapphire, Whilst there might be some variation due to the method of growth, and of course, due to the orientation, this variation is inexplicable. 

Optical Transmission of Sapphire:

The optical transmission range of sapphire is wide, 225-5500mm, extending from UV to IR spectra.

No matter what the optical grades are, IR transmission is not a concern for uncoated sapphire above a wavelength of about 5000 nm. The UV range is where caution should be exercised since the transmission from 140 nm to 240 nm is susceptible to both interstitial vacancies and quite minor amounts of impurities. Although small aperture sapphire windows constructed from the aforementioned Verneuil "half-ingots" often contribute to good transmission, conventional sapphire material tends to demonstrate a poor UV performance at 160 nm to 240 nm. The major factor contributing to poor UV performance, aside from contaminants, is a wide absorption at 205 nm brought upon by interstitial vacancies.

There is also UV-grade sapphire, which is prepared to cater to UV transmission requirements. The UV sapphires will go through specific heat treatments to remove interstitial vacancies, which are reversible using heat.

In the past, the Verneuil Method was developed to fabricate synthetic sapphire. This process makes use of flame fusion. However, due to the difficulties in controlling flame heat, which results in fractures in the final product, and the substantial depletion of Al2O3 during the flame fusion process, which raises the cost of production, this approach is no longer effective in the current market. Moreover, the fact that a natural cleavage plane will be introduced down the middle of the sapphire ingot when using this approach makes it difficult to produce large-diameter sapphires.

For now, the SAPMAC Method and the KY (Kyropoulos) Method are utilized the most often to create optical-grade single-crystal sapphire. The Czochralski method, which the KY method is a modification of, leverages uplifting as the motivating force of growth, and the KY method relies on the delicate modulation of temperature changes to grow sapphire. The apparatus and operations of both methods are analogous.

The sapphires selected to produce Shalom EO's sapphire windows are KY-grown. The KY process involves melting a specific volume of Al2O3 inside a crucible inside a KY growth furnace, then dipping a rod with a seed sapphire crystal connected at the bottom into the resulting solution. The remaining portion of the sapphire crystal is produced utilizing a gradual and slow cooling procedure of the solution after a mild pulling up of the rod is done to extract the first head sector of the sapphire crystal.

The KY method is competent for growing bulk sapphire crystals with diameters greater than 100mm. And because there is little lifting during the growth phase of sapphire, the temperature gradient could be modulated with higher precision, minimizing the densities of lattice dislocation and thermal stress. 

Specifications:

Material Properties:

Applications Notes: The Advantages and Applications of Sapphire Windows

A Window, in the industrial context, is a transparent optical bulk element, functioning to maximize optical transmission within a certain wavelength range of interest or to shield the interior cores from possible damages like scratches, projectiles, high heat, corrosive substances, etc.

Sapphire Windows excel in windows made from other glass counterparts, especially in the aspects of superior surface hardness, durable qualities, and versatile functionalities. Sapphire the second hardest material that existed on earth, with a Mohs value of 9. The high structural integrity of sapphire contributes to its stable mechanical, chemical, thermal, and dielectric properties. So sapphire windows deliver more reliable performances and are often chosen when extreme conditions are encountered.

Sapphire Windows from Shalom EO

What Are The Advantages of Sapphire Windows

• Outlasting Mechanical Strength: Windows manufactured using sapphire are distinguished for their outstanding mechanical strength. Sapphire windows are resistant to scratches and abrasions and could withstand high pressures. The Young’s Modulus of sapphire is twice as large as the Young’s Modulus of Iron, this means sapphire windows are not prone to shape deformation even great forces are exerted. Therefore sapphire windows are often utilized in high-pressure environments like deep-water glass, or operations that confront frequent abrasions and high-speed projectiles, such as outdoor thermal camera windows, phone screens, laser drilling windows, and aerospace windows.
• Wide Optical Transmission: The transmission spectral range of sapphire is about 225-5500nm, extending from the ultraviolet zone to the infrared region. Compared with UV Fused Silica and N-BK7 windows, Sapphire windows have a wider transparent range, allowing uses in UV, VIS, and IR spectra or multi-spectrum transmission.
• Beneficial Thermal Properties: Sapphire windows feature high thermal conduction and are able to work without being affected under high temperatures with a melting point of 2030℃. Therefore sapphire windows are also a suitable candidate for high-power laser windows, plasma chambers, and combustion chambers.
• Chemical Inertia: Sapphire windows are not reactive to those normal acids and alkalis, with the sole exception being hot caustics. This means sapphire windows are sustainable in corrosive environments, such as the seaside and in the field of chemicals and pharmaceuticals.

Industrial: 

The fierce competition of the industrial sector in the modern era necessitates components of better performance and longer life spans to save replacement costs, a fact that points to sapphire windows. Because of its versatile nature and sturdiness, sapphire windows are applied in numerous industries. Furthermore, sapphire windows could be made much thinner and more compact due to their strong atomic bonds, making them a promising selection along with the high integration trend in the photonic and electric market. In addition, sapphire windows are transparent to a wide range of wavelengths, meaning that sapphire windows could support clear vision as sight windows or the designed transmission rate in some critical optical uses such as lasers after anti-reflection coating.

Examples include laser processing windows, plasma chambers, combustion chambers, furnace viewports, barcode readers, fingerprint lock screens, wristwatches, Infrared Windows, etc. 

Here are the reasons:

• High ruggedness that could avoid surface injuries
• Will not deform under high temperatures
• Will not scratch from splatters 
• Strong atomic construction enabling greater diameter-to-thickness ratio
• Broad Transmission encompassing UV, Visible, and IR transmission

Medical/Chemical:

In medical and chemical operations, it is crucial to prevent unintended chemical reactions which could hamper the operation or even lead to devastating consequences, so chemical inertia is an essential condition of the equipment components. Sapphire windows are immune to sorts of chemicals, which renders sapphire windows excellent medical and chemical components.

Examples include endoscopic windows, chemical container viewports, etc.

Here are the reasons:

• No out-gassing or formation of chemical products
• Convenient sanitization, being able to endure autoclave treatments
• outperform glass counterparts

Vehicles:

Sapphire windows could be integrated into vehicles as front car windows, and the windows of LiDAR sets of the airplane, which demands unparalleled protection from high-speed collisions with obstacles and various outdoor climates.

Examples include car windows, airborne Lidar windows, aircraft windows.

Here are the reasons:

• High ruggedness to ensure protection from the nuisance of high kinetic energies during driving
• High resistance against humid weather, water, corrosive atmosphere, and extreme climates
• Lightweight and reduced thickness

Defense:

Components incorporated in the defense sector require the highest standard of reliabilities to deal with all kinds of potential threats and emergencies, in the sense of which, sapphire windows are the rational option with unrivaled robustness.

Examples include submarine glass, the front windows of thermal imaging cameras, military-grade laser windows, etc.

Here are the reasons:

• Unrivaled harness to block potential threats
• Stable performance under variable climates
• High thermal loads to withstand explosives and firing

Hangzhou Shalom EO specializes in producing and providing sapphire windows with a profound engineering background. We optimize with unceasing efforts customer experience and the stages of sapphire window productions, seeking to achieve the best comprise between qualities and prices.

For off-the-shelf sapphire windows, we offer uncoated circular and square sapphire windows with c-cut orientations and diameters/side lengths up to 150mm. The routine specifications of the stocks are 60/40 S/D and 2 lambda flatness, whilst versions with 40/20 S/D and 1/4 lambda flatness are also accessible.

We also provide various kinds of custom sapphire windows including metalized sapphire windows, wedge sapphire windows, stepped sapphire windows, etc of random, c--cut/z-cut orientations and other custom orientations and tailored coatings. We are capable of manufacturing sapphire windows with 10/5 S/D, and 1/10 lambda flatness upon your request.

Note: If you are interested in more knowledge about sapphire windows, click here visit our resource sector to learn more about the Manufacturing Techniques of Sapphire Windows, and the Material Properties of Sapphire