Magneto-optical crystals for isolators


When a light beam passes through a magnetic tool, the Faraday effect causes a rotation in the direction of the light’s polarization; that is, the light beam’s polarization axis rotates clockwise by an angle visible from the viewer’s perspective. If the outbound light is reflected back to the original tool, the onlooker will see that the polarization axis of the light has actually been turned clockwise by the very same angle. A Faraday rotator is an optical rotator that takes advantage of the Faraday effect. Magneto-optical crystals are often used in Faraday isolators and rotators.

Classification of magneto-optical crystals

Magneto-optical crystals are crystalline materials with a magneto-optical effect. Magneto-optical crystals can be divided into three groups:

  • Ferromagnetic magneto-optical crystals
  • Paramagnetic magneto-optical crystals
  • Diamagnetic magneto-optical crystals.

Advantages and applications of magneto-optical crystals

Magneto-optical crystals are extensively utilized in optical communication, computer system storage, microwave gadgets as well as other areas due to their large Faraday result, reduced wavelength absorption coefficient, high leaks in the structure and high magnetization. Magneto-optical crystals can be widely used in optical tool production fields such as optical modulator, optical isolator, optical ring, optical stage shifter, optical switch, in addition to optical storage space, optical screen, optical recorder, microwave tools, laser gyro and other storage space and also microwave device manufacturing areas.


Faraday isolators as well as spinners based on Terbium gallium garnet (TGG) have continued to be the industry requirement until now, as TGG has actually been made use of in the isolators and also rewriters sector as Faraday crystals with modern-day crystal development techniques and also specific control of resources.

TGG crystal is the best magneto-optical material for making a Faraday optometer and isolator, ideal for wavelengths 400–1100 nm (leaving out 470–500 nm). TGG solitary crystal has high magneto-optical continuity, reduced light loss, high thermal conductivity, and a high laser light damage threshold. It is commonly utilized in YAG, Ti-doped sapphire, and various other multistage boosting, ring type, and seed injection lasers.

Magneto-optical crystals for isolators
TGG crystal

The main advantages:

  • Huge magneto-optical constant (35 Rad T-1 m-1)
  • Reduced light loss (<0.1%/ centimeters)
  • High thermal conductivity (7.4 W m-1K-1)
  • High laser damages limit (>1GW/cm2)
  • Large Verdet coefficient (35 Rad T-1 m-1)
  • Low optical losses (<0.1%/ cm)
  • High thermal conductivity (7.4 W m-1K-1)
  • High laser damage threshold (>1GW/cm2)


TSAG is the key isolation product of the future generation fiber laser. As an optimal visible and also infrared magneto-optical crystal, TSAG has the advantages of high Verdet constant, exceptional thermal as well as mechanical homes.

Terbium-scandium-aluminum garnet (TSAG) crystals are perfect magneto-optical materials for both noticeable as well as infrared wavelengths (wavelength array: 400-1600nm). TSAG crystal has the advantages of high stability, great thermal and mechanical buildings, and is a crucial crystal for the future generation of high power laser.

Compared with TGG crystals, TSAG has higher field constant as well as reduced absorption loss, which can make the isolator smaller sized, and is an ideal material for optical isolators with high power.

The main advantages:.

  • Verdet continuous 20% greater than TGG (65radT-1m-1 at 1064nm).
  • Low Absorption(<3000ppm/cm at 1064nm).
  • High power certified.
  • Low thermally-induced birefringence.
  • Make isolator more compactand smaller sized.


Rare earth trifluoride crystals, such as CeF3 and PrF3, are outstanding new magneto-optical materials without “core” and also have high usage rate of crystal spaces.

The Verdet constant worth of CeF3 crystal is the same as that of TGG crystal at 1310nm wave length, which shows that the crystal can be ideal for Faraday isolator in close to infrared band, and turns into one of the potential prospects to change business magneto-optical products.

Faraday rotating glass

Faraday magneto-optical glass (rare-earth Faraday magneto-optical glass) is a new type of useful product that has a wide application potential in the field of fiber optic communication and is also gaining popularity due to its good anisotropic harmony, outstanding magneto-optical properties, and low cost.

Magnetically rotating glass, likewise referred to as Faraday revolving glass, is a new clear optical practical material established in recent decades. It can turn the polarization airplane of a light beam of linearly polarized light alongside the magnetic field. Magnetic optically rotating glass is the core material of high-tech intensive products, which is extensively utilized in the modern areas of optics, electrical power as well as magnetism. As an example, this material can be made use of to make optical isolator, magneto-optical modulator, magneto optical attenuator, magneto optical switch, magneto optical sensing unit as well as a range of high-precision gyroscope in fiber communication.

Verdet Coefficient

Verdet coefficient is an extremely crucial criterion in magneto-optical materials. Although YFeOGdBiFeOz as well as other rare earth iron garnet crystals (YIG) have extremely high Verdet constant and also high passage in the infrared region, they are not clear to visible light, and can only be applied in the infrared region when they are utilized as Faraday rotating components, with challenging growth as well as extended period. The Verdet constant of magneto-optical glass is smaller sized than that of crystal collection, but it reveals strong vitality in the application of magneto-optical gadgets due to a collection of advantages such as good light transmittance, excellent optical uniformity, affordable price, preferred basic materials, especially very easy to produce large-size products.

In addition to figuring out the function of the isolator and the flexibility of the front as well as backside user interfaces, many specifications, such as accuracy, output ripple, temperature level drift, sound, and feedback time, require to be carefully selected by the user.

Read more: Laser Frequency Doubling


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