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Faraday Modulator

Polarization Modulation

Highly stable & sensitive
Includes water cooling system

In Faraday Effect, the phase modulation of two mutually perpendicular components of linearly polarized light results into polarization modulation, which is then transformed into Amplitude Modulation by analyzer. The magneto-optic modulators are based on the rotation of optical polarization as light propagates along the magnetic field in a material, by the Faraday effect. Like intensity modulation, polarization modulation does not require sophisticated stabilized laser. Since, the optical sensitivity of a polarization modulated light is about twice as high as intensity modulated signal, it provides better receiver Signal to noise ratio (SNR).

Our modulator is made of MR3-2 Faraday material placed inside a solenoid coil with modulating electric current. Water cooling system is used for longer operation, for which water inlet and outlet connectors are provided on top of the device.

Since glass material in high power laser system is damaged as a consequence of self focusing, low non-linear refractive index as well as high Verdet constant are important factors for Magnetic Optical Glass. The MR3-2 glass is made by considering all these factors and is stable, sensitive and inherently immune to interference.


HO-FM20C Faraday Modulator



The optical Specifications :


    Faraday Rotator Glass  :  MR3-2 glass

    Verdet constant  :  -0.329 min / Oe*cm at 632.8nm and -0.108 min / Oe*cm at 1064nm

    Absorption coefficient  :  < 0.002 per cm at 1064nm

    Transmission  :  ≥ 86% without AR coating

    Bulk laser damage threshold for material  :  > 25 (Joules/cm²) at 1064nm, 10ns pulses

    For stress birefringence, extinction ratio to perpendicular polarization > 40 dB


Water Cooler for Faraday Modulator

Model Aperture
HO-FM05C 5 mm
HO-FM10C 10 mm
HO-FM015C 15 mm
HO-MOM-FR20C 20 mm

Wavelength Range (nm)

380 - 1100nm

Frequency Range

200 - 5000Hz

Resolution : +/- 1Hz


Applications :

    Polarimetry & Other Optical Rotation Measurements

    Magneto-Optic Kerr Effect

    Faraday Modulation Spectroscopy (FAMOS)

    Optical Communication

The Faraday modulator used for the polarimeter have important function other than providing an easy way of optimizing the signal to noise ratio; it allows the real and imaginary parts of the refractive indices to be separated. This stems from the fact that in the modulator there is very little absorption i.e. the effect is only to modulate the angle of rotation of the linearly polarized laser beam with negligible modulation of the phase or ellipticity of the light.

Faraday Isolator (Optical Isolator)


Faraday isolators are optical components which allow light to travel in only one direction. Their mode of operation is based on the non-linear Faraday effect (magneto rotation). In principle, the function of an optical isolator is analogue to that of an electrical diode. Faraday isolators are composed of three elements: entrance polarizer, Faraday rotator and exit Polarizer.

They are used to protect a laser source from destabilizing feedback or actual damage from back-reflected light. The 5mm aperture Faraday isolators are cylindrically-shaped magneto-optic devices. Strong Neodymium Iron Boron permanent magnets are used to generate high axially-oriented fields within the magnet housing.

In operation, the magnet housing is sandwiched between input and output polarizers that have their transmission axis oriented 90 degrees relative to each other. In the reverse direction the backward traveling beam has a polarization orthogonal to the input polarizer and is therefore crossed with it, resulting in a rejected beam exiting the input polarizer.

We also provide custom designed isolators, based on your requirements. Please feel free to contact us.

Model Center
Wavelength
Aperture Transmission Isolation
Min / Typical
Polarizer Type Rotating Medium Power Handling
HO-FI410 410 nm 5 mm 80 / 82 % 30 dB Calcite MR3-2
Farday Glass
> 25
( Joules/cm² )
at 1064 nm
10 ns pulses
HO-FI532 532 nm 85 / 89 % 36 / 40 dB
HO-FI632 632.8 nm 85 / 89 % 36 / 38 dB
HO-FI650 650 nm 85 / 89 % 36 / 38 dB
HO-FI785 785 nm 85 / 89 % 36 / 38 dB

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