TGG (terbium gallium garnet) and TSAG (terbium scandium aluminum garnet) are magneto-optical crystal materials used in Faraday-rotation applications. Comparing them requires the operating wavelength, temperature, magnetic-field arrangement and optical loading conditions. A higher Verdet constant alone does not establish the isolation ratio or power rating of a finished device.
Compare Verdet constants under matching conditions
The Verdet constant describes the material’s Faraday rotation response to a magnetic field. Compare values at the same wavelength and temperature, and confirm the measurement method and crystal orientation.
A 2018 laser study by Guo and colleagues used a TSAG-based optical diode and reported a higher Verdet constant than the TGG reference at 1064 nm. This is evidence for the materials and conditions discussed in that paper, not a universal percentage advantage for every TSAG crystal.
Why absorption and thermal effects matter
Research on TGG shows that absorbed optical power can create temperature gradients and thermally induced depolarization. These effects can limit isolation performance. Beam size, optical power, crystal orientation and thermal handling therefore belong in the comparison alongside the Verdet constant.
Request absorption data at the intended operating wavelength and distinguish bulk absorption from coating and surface losses. A material comparison or supplier reference table does not establish the performance of a complete isolator.
TGG and TSAG comparison checklist
| Comparison item | What to confirm for both materials |
|---|---|
| Verdet constant | Value, sign convention, wavelength, temperature and measurement conditions |
| Optical absorption | Measurement wavelength, method and whether surface or coating losses are included |
| Crystal geometry | Length, diameter or aperture, orientation and dimensional tolerances |
| Operating conditions | CW or pulsed operation, power or pulse energy, beam size and temperature range |
| Optical surfaces | Polish, coating wavelengths, incidence angles and inspection criteria |
| Assembly evaluation | Magnet arrangement, mounting, cooling and the required isolation test |
Prepare a material inquiry
Send the component drawing, operating wavelength, optical loading conditions and required inspection records through our technical sales contact page. Identify whether you need a bare crystal or another component configuration. Material availability and the scope of supply must be confirmed before quotation.
Browse the current ATR Crystal product range for listed materials. This article is a technical comparison, not a specification for a complete Faraday isolator.
Technical references
- Guo et al., Realization of a 101 W single-frequency continuous wave all-solid-state 1064 nm laser by means of mode self-reproduction, Optics Letters, 2018. DOI: 10.1364/OL.43.006017.
- Khazanov et al., Investigation of Self-Induced Depolarization of Laser Radiation in Terbium Gallium Garnet, IEEE Journal of Quantum Electronics, 1999.
These publications describe the authors’ research and are not ATR batch inspection reports.