What are Ball lenses and Half-ball lenses:
Ball lenses belong to a special form of biconvex lenses which have the geometries of a ball(sphere). They are manufactured from a single material, often optical glass with good transparency in the wavelength region of interest. Ball lenses are often utilized to focus or collimate light as fiber optics (e.g. laser-to- fiber coupling, fiber-to-fiber coupling) depending on the geometries of the input light source. Also, ball lenses could be ball pre-forms of aspheric lenses where the lenses are deformed in purpose in order to prevent spherical aberrations.
Half-Ball lenses are variants of ball lenses, obtained through cutting the ball lenses in half. Due to the ease of mounting derived from the one flat surface, half-ball lenses are ideal for applications where more compact designs are required, such as fiber communication, endoscopes, microscopes, optical pick-up devices, and laser measurement facilities.
There are three essential parameters of ball lenses and half-ball lenses. One is the effective focal length (EFL), which is the distance between a plane through the center of the lens and the beam waist (focus) of an input beam collimated at the initial. Another is back focal length (BFL), defined as the distance of the focal point from the lens surface, therefore half the diameter smaller than the EFL. The calculation equations OF EFL and BFL are given in the technical images, please check the technical images if you are interested. And the last is the numerical aperture (NA), during the collimation course of the incident light, the numerical aperture (NA) of the ball lens is dependent on the diameter of the ball lens (D), its index of refraction (n), and the diameter of the input source (d). Simply put, the numerical aperture is proportionate to the resolution of the lens, the larger the NA, the more light collected using the lens. And the equation is also given in the technical image.
Hangzhou Shalom EO provides both stocked and custom ball lenses and half-ball lenses made from Sapphire. The specification of the custom ball and half ball lenses could be varied upon your request.
Here are some important features of Sapphire:
Optical-grade Sapphires chosen to produce optical components are Alpha Single Crystal Sapphires, chemical formula Al2O3, with a wide transmission range from 0.225-5.5μm. Sapphire has a hexagonal structure. The lattice constant is a=b=4.758A, c=12.991A, and the refractive index is 1.762-1.770. Its strong covalent bonds contribute to the enduring and solid nature of sapphire. Its Mohs hardness is 9, ranking right after diamond, and its anti-compression strength is between 1.9-24 GPa. And Young’s Modulus of sapphire is 380Gpa, which is about twice the magnitude of iron’s. The melting temperature of sapphire is high,2045 °C, which enables sapphire to be engaged in manifolds of applications requiring high thermal loads.
Sapphire lenses are ideal for demanding applications because of their eminent performance, consisting of superior surface hardness ( 9 on the Mohs scale, the third hardest mineral, after diamond at 10 and moissanite at 9.5, which means high resistance to scratch and abrasion), high thermal conductivities, outstanding dielectric properties and resistance to common chemical acids and alkalis. In addition, sapphire features a high index of refraction and excellent broadband transmission characteristics.
|Materials||Optical grade sapphire crystals||Diameter Range||~300mm|
|Diameter Tolerance||+0.0/-0.2mm||Thickness Tolerance||+/-0.2mm|
|Surface Quality||60/40 S/D||Frings (N)||3|
|Irregularity (delta N)||1||Centration||3'|
Physical and Optical Properties:
|Transmission Range||0.17 to 5.5 μm||Refractive Index||No 1.75449; Ne 1.74663 at 1.06 μm (1)|
|Reflection Loss||14% at 1.06 μm||Absorption Coefficient||0.3 x 10-3 cm-1 at 2.4 μm(2)|
|Reststrahlen Peak||13.5 μm||dn/dT||13.1 x 10-6 at 0.546 μm(3)|
|dn/dμ = 0||1.5 μm||Density||3.97 g/cc|
|Melting Point||2040°C||Thermal Conductivity||27.21 W m-1 K-1 at 300K|
|Thermal Expansion||5.6 (para) & 5.0 (perp)x 10-6/K*||Hardness||Knoop 2000 with 2000gindenter|
|Specific Heat Capacity||763 J Kg-1 K-1 at 293K(4)||Dielectric Constant||11.5 (para) 9.4 (perp) 、at 1MHz|
|Youngs Modulus (E)||335 GPa||Shear Modulus (G)||148.1 GPa|
|Bulk Modulus (K)||240 GPa||Elastic Coefficients||C11=496 C12=164 C13=115 C33=498 C44=148|
|Apparent Elastic Limit||300 MPa (45,000 psi)||Poisson Ratio||0.25|
|Solubility||98 x 10-6 g/100g water||Molecular Weight||101.96|
|Class/Structure||Trigonal (hex), R3c|
1. Transmission of Sapphire at Infrared wavelength range (no coating)
2. Transmission of Sapphire at UV wavelength range ( no coating)