Faraday rotators and Faraday mirrors · Non-reciprocal 45° rotation, wavelength band, rotation tolerance, extinction ratio, insertion loss, aperture and power
A Faraday rotator turns the polarization plane of light in a magneto-optic material inside a magnet, and keeps turning it the same way on the return pass, so light going back through it is rotated twice. That non-reciprocal behaviour is what makes optical isolators and Faraday mirrors work. Settle three things before ordering: the wavelength band and format, the optical power and aperture, and the rotation accuracy, extinction ratio and loss the system can tolerate.
Free-space Faraday rotators, in-line fibre Faraday rotators and Faraday rotator mirrors for lasers, amplifiers and fibre sensors. Complete optical isolators and circulators, wave plates, polarizers and electro-optic modulators are outside this page.
01
ModuOptik, a maker of free-space Faraday rotators, explains that its rotator gives non-reciprocal rotation while keeping the beam linearly polarized: one pass rotates the polarization by 45°, and the return pass adds another 45° in the same direction relative to the magnetic field. Its TGG rotators for 1064 nm are listed with a 3 mm aperture at 30 W average power and over 98% transmittance, and a 5 mm aperture at 50 W and over 97%, both with extinction ratio above 30 dB; an 820 nm version is also listed. [1]
For fibre systems, AFR describes a polarization-maintaining Faraday mirror as a passive device that rotates the polarization state by 90° on reflection, used in amplifiers, fibre lasers and fibre instruments to minimize polarization effects. [2] DK Photonics lists in-line Faraday rotators and Faraday mirrors from 1030 and 1064 nm through 1310, 1480 and 1550 nm to 1950–2050 nm. [3]
Editorial calculation: 45° on each of two passes gives 90° in total, which is why a Faraday mirror returns light in the orthogonal polarization state. [1] [2]
Give the supplier the centre wavelength and band, format (free-space rotator, in-line fibre rotator or Faraday mirror), fibre type and connectors, aperture, average and peak power or pulse energy, required rotation angle and tolerance, extinction ratio, insertion loss, operating temperature and quantity.
02
AFR's PM Faraday mirror datasheet lists centre wavelengths of 1310, 1480 or 1550 nm with an operating band of ±15 nm, 45° single-pass Faraday rotation with a maximum tolerance of ±1° at the centre wavelength and 23 °C, insertion loss of 0.4 dB (typ.) and 0.6 dB maximum, minimum extinction ratio of 20 dB, PM Panda fibre, 300 mW maximum CW power, 5 N maximum tensile load, −5 to +70 °C operation and −40 to +85 °C storage. Each added connector raises loss by 0.3 dB and lowers return loss by 5 dB and extinction ratio by 2 dB. [2]
Editorial calculation: adding one connector to the AFR mirror raises its 0.4 dB (typ.) insertion loss to about 0.7 dB (0.4 + 0.3) and lowers its minimum extinction ratio to about 18 dB (20 − 2). [2]
Editorial note: rotation angle depends on wavelength and temperature in magneto-optic materials, which is why AFR states the tolerance at the centre wavelength and 23 °C; ask for the angle at the edges of your band and temperature range.
03
The rotation in a free-space rotator comes from the magneto-optic crystal inside the magnet. Laser Crylink, a crystal grower, lists terbium gallium garnet (TGG, Tb3Ga5O12) for 400–470 nm and 500–1500 nm, with optical losses below 0.1%/cm, laser damage threshold above 1 GW/cm², refractive index 1.954 at 1064 nm, Mohs hardness 8 and an extinction ratio of 30 dB over 2/3 of the clear aperture. Its property table gives a Verdet constant of −134 rad·T⁻¹·m⁻¹ at 632 nm and −40 rad·T⁻¹·m⁻¹ at 1064 nm; the introduction on the same page quotes 35 rad·T⁻¹·m⁻¹ at 1064 nm, so confirm the value used for your design with the crystal supplier. [4]
Rotation angle equals Verdet constant × magnetic flux density × crystal length, so a 45° (π/4 rad) rotator needs a crystal length of 0.785 ÷ (V × B). Editorial calculation: at 1064 nm with V = 40 rad·T⁻¹·m⁻¹ and B = 1 T, L ≈ 19.6 mm; with V = 35 rad·T⁻¹·m⁻¹, L ≈ 22.4 mm; at 632 nm with V = 134 rad·T⁻¹·m⁻¹, L ≈ 5.9 mm. [4]
The supplier also states that TGG has twice the Verdet constant of a terbium-doped glass, and its example blanks for rotators and isolators include φ13 × 4 mm and 10 × 10 × 10 mm in [111] orientation and Ø3.2 × 25 mm with 1064 nm anti-reflection coating on both sides. [4]
Editorial note: a longer wavelength or a weaker magnet calls for a longer crystal, which adds absorption and thermal lensing at high power; ask the rotator maker for the crystal material, length and field at your wavelength.
04
The listings reviewed cover free-space TGG rotators for high-power lasers and fibre Faraday rotators and mirrors from about 1 to 2 µm; ask each for rotation angle and tolerance across band and temperature, extinction ratio, insertion and return loss, and power or damage rating.
05
The crystal and magnet rows set the 45° rotation; on a fibre mirror the connector row also moves loss and extinction ratio. [1] [2]
| Part | Role | Fix in the order |
|---|---|---|
| Magneto-optic crystal | Sets rotation; TGG listed. [1] | Material; length. |
| Magnet | Provides the axial field. [1] | Size; field. |
| Aperture | Beam size and power. [1] | Diameter. |
| Mirror (Faraday mirror) | Returns light for second pass. [2] | Coating; wavelength. |
| Fibre and connectors | PM fibre; added loss per connector. [2] | Fibre; connector. |
| Housing | Protects alignment; tensile limit. [2] | Package. |
06
Free-space and fibre devices are specified differently here: aperture and average power for the TGG rotators, connectors and CW power for the fibre mirror. [1] [2]
| Field | What it means and published values | Ask the supplier for |
|---|---|---|
| Wavelength Range (nm) | λc ± 15 nm example; 820–2050 nm offered. [2] [1] [3] | Band. |
| Aperture Diameter (mm) | 3 or 5 mm (free-space TGG). [1] | Aperture. |
| Rotation Angle (°) | 45° single pass, ±1° at λc, 23 °C. [2] | Angle and tolerance over band. |
| Insertion Loss (dB) | 0.4 (typ.), 0.6 max (fibre mirror). [2] | With connectors. |
| Extinction Ratio (dB) | >30 (free-space); ≥20 (fibre mirror). [1] [2] | Minimum. |
| Power handling and damage threshold | Average power 30–50 W listed (free-space) [1]; TGG crystal damage threshold above 1 GW/cm². [4] | Pulse damage threshold. |
| Operating Temperature (°C) | −5 to +70 (fibre mirror). [2] | Range. |
| Storage Temperature (°C) | −40 to +85. [2] | Range. |
| Relative Humidity (%) | Package limit. | Range. |
| Material | TGG crystal (free-space example). [1] | Crystal. |
| Weight (g) | Per device. | Weight. |
07
Paste it into your enquiry below or into an email to a maker, then replace every bracket.
Wavelength: [centre; band] Format: [free-space rotator; fibre rotator; Faraday mirror] Power: [average; peak; pulse energy] Aperture/fibre: [mm; fibre type; connectors] Performance: [angle tolerance; extinction; loss] Environment: [temperature range] Quantity: [units]
Hefei ModuOptik lists free-space TGG rotators for 1064 nm and 820 nm; Advanced Fiber Resources lists PM and standard Faraday mirrors from 1064 to 2070 nm; DK Photonics lists in-line rotators and mirrors from 1030 to 2050 nm.
Lists free-space TGG Faraday rotators for 1064 nm and 820 nm.
Product scope checked 2026-10-11
Lists PM and standard Faraday mirrors from 1064 to 2070 nm.
Product scope checked 2026-10-11
Lists in-line Faraday rotators and Faraday mirrors from 1030 to 2050 nm.
Product scope checked 2026-10-11
Explore company information and manufacturing capabilities, then discuss the scope of your project with a relevant supplier.
ModuOptik says the return pass rotates polarization another 45° in the same direction relative to the field. [1]
AFR describes it as rotating the polarization state of returned light by 90°. [2]
ModuOptik lists 1064 nm TGG rotators at 30 W (3 mm) and 50 W (5 mm) average power. [1]
AFR specifies ±1° at the centre wavelength and 23 °C for its PM Faraday mirror. [2]
Terbium gallium garnet (TGG) is one choice: Laser Crylink lists a Verdet constant of −40 rad·T⁻¹·m⁻¹ at 1064 nm, losses below 0.1%/cm and damage threshold above 1 GW/cm², so a 45° rotator at 1 T needs about 19.6 mm of crystal (Editorial calculation). [4]
Sources checked 2026-10-11. ModuOptik, AFR and DK Photonics are optical component makers publishing Faraday rotator and mirror specifications; all three are linked suppliers. Laser Crylink publishes TGG magneto-optic crystal properties.
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