Category: Rotator

What are Faraday Rotators and Isolators and where are they used?

When it comes to transmission of light signals, the “Polarization State” is one of the important characteristics that you need to focus on and Faraday rotators and isolators are those devices which help engineers to take care of it. So, today, we have decided to share the basic information about these crucial devices and their applications.

Faraday Rotator and Its Applications

It is a magneto-optic device which employs Faraday Effect to rotate the polarization state. In this device, the light is transferred through a transparent medium which is exposed to the magnetic field. The direction of magnetic field lines is approximately the same or the opposite as the direction of the beam.

If light is linearly polarized in some direction, this direction is continuously rotated while passing through the medium. When a linearly polarized beam is passed through a Faraday rotator and back again after reflecting in a mirror, the polarization changes of the two passes add up instead of canceling. This non-reciprocal behavior of Faraday rotator is what makes it distinct from other arrangements such as waveplates and polarizers.

Applications:

High power Faraday rotators are widely used in laser technology. Some of its major applications are:

  • One of the most common applications of Faraday rotators is in Faraday isolators for protection of lasers and amplifiers against back-reflected light. In this application, the rotation angle should be close to 45 degrees in a particular spectral region. Highly uniform polarization rotation is required for attaining high attenuation for back-reflected light.
  • A Faraday rotator is also used in a ring laser resonator for introducing round-trip losses that depend on the direction and, thereby, enforce unidirectional operation. Since only a very small difference of loss is enough most times, a Faraday rotator will be helpful to facilitate a small rotation angle.
  • It can be used for Faraday mirrors which help in achieving a polarization direction that is orthogonal to that of the input beam even if the polarization state is not preserved by the amplifier. It works better than using a Faraday isolator, an amplifier, and an ordinary mirror.
  • It is also used in interferometers because polarization state changes through the fiber are canceled out on the return trip.

Faraday Isolator and Its Applications

A Faraday isolator is typically an optic isolator which transmits light in a certain direction while blocking light in the opposite direction. They are variants of optical circulators having at least three ports and based on Faraday rotators.

Types:

Polarization Sensitive Faraday Isolators

It is the simplest one because it functions only when the input beam has a fixed direction of linear polarization.

Polarization Insensitive Faraday Isolators

This Faraday isolator is a device which works for arbitrary polarization of the input beam and therefore, it is widely used in fiber optics as many fibers don’t maintain polarization.

Applications:

  • They are sometimes used for protecting laser or amplifier against back-reflected light. Some amplifier chains contain several isolators between different stages not only for protection purposes but also for amplified spontaneous emission.
  • The polarizing property of a polarization-dependent isolator can be used within a laser resonator for enforcing linear polarization state or for mode locking with a nonlinear polarization rotation.

So, both high power Faraday rotators and isolators play a significant role in electronics and telecommunication industry.

High Power Faraday Rotator and Isolator: Key Features and Top Benefits

From multi-level laser amplifier, ring laser to the optical modulator, the Faraday rotator and isolator is a key component in a wide range of devices used in diverse verticals today. It plays a vital role in how these devices perform. Or in other words, the efficiency of these devices largely depends on faraday rotator and isolator. As to help you why you should invest in those, we will discuss those two vital components from every perspective – keys features, applications, and benefits.

What are faraday isolator and rotator?

The Faraday rotator is a polarization rotator that works on the Faraday Effect, and this is a reason the component is called Faraday rotator.  The component also based on magnetic effect. It works because one polarization of the light received is in the ferromagnetic resonance with the object which increases the phase velocity more than the other.

 Faraday rotator changes the polarization state of light that is run through it. As a result, the output polarization state is caused to move around by 45 degrees with respect to the input polarization.  When combined with mirror, the light reflected starts rotating by another 45 degrees, and this all results in a 90-degree rotation.  Moreover, the polarization handedness is reversed by the mirror, which results in a reflected polarization orthogonal to the original polarization. This is of immense importance if used in interferometers as the polarization changes through the fiber and is canceled out on the return journey.

While an optical isolator also known as an optical diode is an optical component that allows the transmission of light in only one direction.  The use of this component is meant to prevent unwanted feedbacks into the device called optical oscillator such as a laser cavity.

The component comes in various series. The high power series include in-line type, beam expanded and fiber-in and free space out isolators.  For example, 1064nm High Power Free-Space Isolator belongs to free space in and out isolator which is widely used in fiber laser and instrumentation applications.

Prime Applications

These two components have a slew of applications ranging from Multi-level laser amp to a number of instrumentation applications. It makes no sense discussing each and every use of those components here in the blog post. Instead, we will try to throw light on some of the most crucial applications. Below are some of their crucial uses.

  • Multi-level laser amplifier
  • Ring laser
  • Erbium-doped fiber amplifier
  • Seed injecting laser
  • Optical modulator

Top benefits that make these components ideal choice

No matter what you do as a business outfit, to sustain and get an edge in this hyper-competitive world, you must work towards cutting on unwanted cost, follow highest standards in your domain, and provide top quality for low cost. And this is what Faraday rotators and isolators are all about. Some of the top benefits the components offer include low insertion loss, low cost, RoHS compliant, high reliability, high power handling and high isolation.