Crystal Systems - Sapphire Grades

Advantages of HEM^TM Sapphire
One of the major advantages to the Heat Exchanger Method (HEM) of crystal growth is an isothermal environment created in the furnace after solidification of the crystal. After crystal growth is complete, the furnace temperature is below the solidification temperature and the heat exchanger temperature is increased; thereby in situ annealing of the boule is achieved prior to controlled cooldown to room temperature. In situ annealing of sapphire boules after growth relieves stress and reduces lattice defects introduced during cooldown.

Detecting Sapphire's Quality
Crystal Systems has developed a matrix defining standards for characterizing HEM sapphire into five classes based upon lattice distortion and light scattering. Lattice distortion is detected by examination of sapphire between cross polarizers; light scatter is detected by illuminating sapphire with an intense white light source in a dark room.

HEM^TM Sapphire Quality Matrix
HEM sapphire, available in five grades, is selected for specific applications and priced according to quality. The transmission of all grades is above 80% in the non-vacuum spectrum (from 0.25 to 4.5 mm) and all grades are available in a variety of orientations: (0001), (1010), (1102) and (1120). Because of our consistency in material selection and the outstanding quality of our material, many customers specify one of our quality levels in their design criteria. HEM sapphire grade for specific applications is a reliable choice, since customers are not sold a higher priced product if a lower grade can meet their requirement.

HEMEX is the premium grade, the highest quality sapphire available worldwide and the only sapphire free of light scatter and lattice distortions. This sapphire grade is used in applications that demand crystal perfection, with no compromises.

HEMLUX is a superior grade of sapphire with minimal light scatter and/or lattice distortions, used primarily in optical applications with more stringent requirements than standard optical grade material.

HEMLITE is a standard optical grade material with limited light scatter and/or lattice distortion. Available in diameters up to 10 inches for windows and laser optics, other applications include infrared (IR) windows and lenses, laser windows and tubes and maser cavities.

HEMCOR is a versatile grade available in diameters up to 12 inches, with modest amounts of light scatter and/or lattice distortion. Used for many optical applications and for Light Emitting Diodes (LED) and Laser Diode (LD) applications. Many advanced manufacturers of blue Laser Diodes (LD) prefer this grade of material.

HEMVERNEUIL is an economical grade equivalent to material produced using the flame fusion (Verneuil) growth technique, but of higher purity. It is available in diameters up to 12.5 inches with stronger light scatter and/or lattice distortion. Suitable for some light emitting diode (LED) wafers, wafer carriers, and mechanical and structural applications such as bearings and fixtures.