A TGG Crystal, also known as a Terbium Gallium Garnet Crystal, is a high‑performance Magneto-Optical Crystal widely used for Faraday rotation in laser systems. As a High Verdet Constant Crystal, it enables efficient non‑reciprocal polarization rotation and serves as the active element in TGG Faraday Rotator and TGG Optical Isolator Crystal assemblies. Combining low optical absorption, excellent thermal properties, and high laser damage resistance, TGG crystals are commonly integrated with optical isolators, laser optics, polarizers, waveplates, and other optical components, while specialized coatings help maximize transmission and system efficiency.
Crystals available from stock
Description
A TGG Crystal, also known as a Terbium Gallium Garnet Crystal, is a specialized Magneto-Optical Crystal designed for Faraday rotation in high-power laser systems. Owing to its high Verdet constant, low optical absorption, and excellent thermal properties, TGG is widely used as the active material in Faraday rotators and optical isolators. As a High Verdet Constant Crystal, it enables efficient polarization rotation in the presence of a magnetic field, making it one of the most widely used magneto-optical materials for protecting laser sources from harmful back reflections.
A TGG Faraday Rotator operates by rotating the plane of polarization in proportion to the magnetic field strength and optical path length through the crystal. Unlike reciprocal polarization components, the Faraday effect is non-reciprocal, allowing TGG to serve as the core element of optical isolation systems. As a TGG Optical Isolator Crystal, it is commonly integrated into laser cavities and free-space optical systems to improve laser stability and suppress optical feedback.
The performance of a TGG Crystal depends on several parameters, including crystal dimensions, orientation, optical quality, wavelength range, and surface finish. Anti-reflection coatings may be applied to the entrance and exit surfaces to reduce Fresnel reflections and maximize transmission at the operating wavelength. The choice of coating therefore depends on laser wavelength and application requirements, with optimized coatings improving transmission efficiency and minimizing insertion loss.
TGG crystals also provide excellent resistance to laser-induced damage, good thermal conductivity, and stable operation under high optical power densities. These characteristics make them especially suitable for demanding laser environments where thermal effects and long-term reliability are critical. Within complete laser assemblies, TGG crystals are frequently used alongside optical isolators, laser optics, polarizers, waveplates, and other optical components.
Key Features
- High Verdet constant for efficient Faraday rotation;
- Functions as a High Verdet Constant Crystal for magneto-optical applications;
- Non-reciprocal polarization rotation based on the Faraday effect;
- Low optical absorption for high transmission and reduced thermal loading;
- Excellent thermal conductivity for stable operation under high optical power;
- High resistance to laser-induced damage;
- Suitable for continuous-wave and pulsed laser systems;
- Available with anti-reflection coatings optimized for specific wavelengths;
- Performance depends on crystal dimensions, orientation, optical quality, and surface finish;
- Widely used in TGG Faraday Rotator and TGG Optical Isolator Crystal assemblies.
Applications
- TGG Faraday Rotator systems for polarization control;
- Optical isolators for suppressing back reflections and protecting laser sources;
- High-power solid-state laser systems;
- Fiber laser and diode-pumped laser assemblies;
- Industrial laser systems requiring optical feedback suppression;
- Scientific and research laser instrumentation;
- Precision optical measurement systems;
- High-power photonics applications requiring stable magneto-optical performance;
- Laser beam delivery systems requiring reliable isolation and polarization control.
Specifications
Product Specifications
| Chemical formula | Tb3Ga5O12 (terbium gallium garnet) |
| Optical symmetry | Isotropic (cubic) |
| Crystal structure | cubic (garnet, space group Ia3d) |
| Lattice constants | a = 12.355 Å |
| Density | 7.13 g/cm³ |
| Mohs hardness | 8 |
| Melting point | 1725 °C |
| Refractive index (at 1064 nm) | 1.954 |
| Thermal conductivity coefficient | K = 7.4 Wm-1K-1 |
| Verdet constant | V = 38.5 rad T-1m-1 @ 1064 nm |
| Termal expansion coefficient | α = 7.3 x 10-6 °C-1 |
| Direct band-gap energy (293 K) | Eg ≈ 3.8 eV |
| Transparency range | 400–1100 nm (except 470–500 nm) |
Standard manufacturing specifications
| Cut orientation: | [111] +/- 15 arcmin |
| Dimensions tolerance: | Ø +0/-0.05 mm, L +/- 0.2 mm |
| Clear aperture: | 90% of aperture dimensions |
| Surface quality: | 10-5 S-D |
| Surface flatness: | < λ/10 @ 633 nm |
| Parallelism: | < 10 arcsec |
| Perpendicularity: | < 5 arcmin |
