CeF3 crystal has paramagnetic rotation characteristics. Among the rare earth (RE3+) ions, fluoride crystals generally have higher UV-VIS-IR transparency than oxide crystals. At the same time, Ce3+ is characterized by complete transparency in the VIS region. However, the TGG material traditionally used as a Faraday rotator (FR) has a continuous decrease in transparency toward shorter wavelengths in the visible (VIS) wavelength region, resulting in optical loss and loss of equipment performance and other adverse effects. Therefore, in the uncovered UV and VIS wavelength regions, the use of cerium fluoride crystals as FR has considerable potential.
The magneto-optical properties of CeF3 crystal enable it to be used as a Faraday rotator used in the field of high-power lasers
CeF3 crystal is transparent in the spectral range up to 2.5µm. As a consequence, it can be used as a 2µm Faraday device, and similarly, it is a paramagnetic material. In the 1.86 − 2.3 µm spectral range, the Verdet constant is approximately 9–5 rad / Tm (absolute value). In order for the CeF3 crystal to reach the Faraday rotation angle required by the standard, a relatively strong magnetic field or multiple magneto-optical elements will be required. Another significant advantage keeps that the possibility of producing large-aperture (up to ~10 cm) optical elements remain available for CeF3 in high-power laser systems. In this respect CeF3 surpasses most of the magneto-active crystal media. For example, the largest aperture of a TGG single crystal with quality fit for producing an FI is only 40 mm.
|Melting point (℃)||1443|
|Refractive index @400nm||1.62|
|Growth Method||Bridgman Stockbarger|
|Verdet Constant(450 nm)||247 rad/T|
|Verdet Constant(532 nm)||180 rad/T|
|Verdet Constant(633 nm)||129 rad/T|
|Verdet Constant(810 nm)||63 rad/T|
|Verdet Constant(980 nm)||44 rad/T|
|Verdet Constant(1075 nm)||33 rad/T|
|Verdet Constant(1310 nm)||10 rad/T|
|Verdet Constant(1940 nm)||10.1 rad/T|
|Laser Host Material,Emission Wavelength||CeF3 Crystal,V [rad/Tm] (L45 [mm])|
|Tm:silica fiber, 1.86 µm||– 9.2 ± 0.1 (∼53.2)|
|Tm:germanate fiber, 1.90 µm||– 8.7 ± 0.1 (∼56.5)|
|Tm:silica fiber, 1.94 µm||– 8.2 ± 0.1 (∼60.0)|
|Tm:YAG, 2.01 µm||– 7.4 ± 0.1 (∼66.5)|
|Ho:YLF, 2.05 µm||– 7.0 ± 0.1 (∼70.5)|
|Ho:YAG, 2.10 µm||– 6.5 ± 0.1 (∼75.9)|
|Tm:YLF, 2.30 µm||– 4.8 ± 0.1 (∼102.2) * 185 ± 15 (∼4.2)|
An L45 length of a magneto-optical element needed for a 45-degree polarization plane rotation is specifified in the brackets for all of the investigated materials.
- is transparent up to 2.5 µm and, therefore, it is also used for the 2-µm Faraday devices.
- has a ∼9–5 rad/Tm (in the absolute value) Verdet constant in the 1.86 6 2.3 µm spectral region.
- Relatively strong magnetic fields or multiple magneto-optical elements would be needed to achieve the standardly needed Faraday rotation angles using the CeF3 crystal, nevertheless, the technology to fabricate this material in large sizes is already available.
- Verdet constant dispersion data in the 2-µm spectral region may be approximated (with a <15% accuracy) by a model, which considers contributions of a single, most dominant electric dipole transition located at approximately 0.234 µm.
Faraday rotator used in the field of high-power lasers