Functional Crystals

OST Photonics offers various functional crystal materials for laser systems, optical equipment and instruments. Crystals are divided into six types according to their functions: laser crystals (diffusion bonding crystals, Nd:YAG, Er:YAG, Yb:YAG, CTH:YAG, Nd:Ce:YAG, Nd:YVO4, Nd:GdVO4, Nd:YLF, Pr:YLF, Ho:YLF, Tm:YLF, Ti:Sapphire, Er:Yb: Glass), nonlinear crystals (KDP & DKDP), KTP, LiNbO3, LBO, BBO, BIBO), passive Q-switch crystals (Cr4+:YAG, Co2+:MgAl2O4), birefringent crystals (YVO4, α-BBO), Magneto-optic Crystals (TGG) and optical crystals (BaF2, CaF2, MgF2, LiF, Germanium single crystal, Sapphire (Al2O3), YAG, ZnSe, Silicon single crystal, ZnS). If you want to know more about our functional crystals, please do not hesitate to contact OST Photonics.

What are Functional Crystals?

A wide range of functional crystal materials is used in various optical applications. While optical glass is commonly used as a transparent material, different functional crystal materials, primarily monocrystalline materials, are required for diverse applications due to their unique functionalities:

In contrast to glass, birefringent crystals can exhibit birefringence, which is a requirement for various types of polarizers, wave plates, birefringent tuners, and other optical components. Commonly used birefringent crystal materials include YVO4, α-BBO, quartz, calcite and sapphire.

The lattice symmetry of a crystal material is not too high (such as a triangular, quadrilateral, or single prism), and it can exhibit nonlinearity. Nonlinear crystals are primarily used for nonlinear frequency conversion but also find applications in optical modulators like the Pokel cell.

A wide variety of functional crystal materials can be used as laser crystals, serving as host materials for laser-active dopants (rare earth ions or transition metal ions). They typically exhibit relatively high transition cross sections, small gain bandwidth, and good heat conduction compared to laser-active glasses. In general, they also allow for higher doping concentrations.

In some cases, functional crystal materials are used in spectral regions where glass does not have a wide enough wavelength range and high transmittance. In particular, various materials such as zinc sulfide (ZnS), zinc selenide (ZnSe) and Sapphire (Al2O3) are used as infrared crystals, and other materials such as lithium fluoride (LiF), calcium fluoride (CaF2) and magnesium fluoride (MgF2) are used as ultraviolet crystals.

Some functional crystal materials, such as terbium gallium garnet (TGG), exhibit the Faraday effect (polarization rotation caused by magnetic fields), and they can be utilized in devices like Faraday rotators and Faraday isolators.

The pyroelectric effect in some functional crystal materials, such as lithium niobate (LiNbO3) and lithium tantalate (LiTaO3), is exploited in pyroelectric detectors.

The scintillation crystal materials have the capability to detect radiation.

Most optical crystals are insulating (dielectric) materials with wide band gaps and very low absorptivity in the visible spectral region. However, there are also semiconductors that are used as optical crystals, for example as infrared optical crystals, where strong absorption in the visible region is not correlated.

Functional crystals have a wide range of geometric shapes, from simple cubes to cylinders and other shapes with curved surfaces.

What is a Diode Pumped Solid State Laser (DPSS)?

DPSS is short name for Diode Pumped Solid State (DPSS) Lasers.

Diode pumped solid-state (DPSS) lasers are solid-state lasers pumped by laser diodes. They emit very short nanosecond pulses with high peak power and repetition rates, while generating minimal heat. These lasers are available in a variety of different wavelengths with very good beam quality. The gain medium of these lasers is glass or crystals doped with impurities, such as neodymium, chromium, erbium, or other ions. This gain medium is placed between two mirror surfaces. The main laser crystals used in this laser are neodymium-doped yttrium aluminum garnet (Nd:YAG), neodymium-doped yttrium orthovanadate (Nd:YVO4) and potassium titanium phosphate (KTP). KTP crystals are sensitive to optical damage at extremely high output levels. DPSS lasers are optically pumped with a diode module with a long life. Because the laser diode has a low noise intensity, the noise of the diode-pumped laser is also very low.

DPSS laser is a continuous wave laser that can also operate in pulse mode through a Q-switch. These lasers are very sensitive to temperature. Compared to flash pumped lasers, their design is more compact, the laser head is smaller, and they are very efficient, reliable, and flexible. This type of laser may generate harmonics, allowing wavelengths from ultraviolet to infrared to be emitted. The commonly used DPSS laser is a 532 nanometer green laser. DPSS lasers utilize the narrow linewidth and high brightness characteristics of diode lasers. This leads to maximum absorption, thereby improving efficiency.