Laser !

[Pelin Sule]

Hello!
I would like to ask, why do we need polarization in laser optics?
Thanks
Pelin

[Ahmad Mustafa]

Hi Pelin,

Well, Polarization is a basic property associated with light just like its Amplitude, Phase, Frequency. There could be many applications in which polarization of light can be used e.g. in Polrization modulation where you modulate the polarization of your optical carrier to transmit data. Another application where polarization can be made use of is called Polarization Division Multiplexing where you transmit data in both the orthogonal polarization of light. In this case, you trasmit twice the data using the same Bandwidth.

Attached you will find the quite opened Eye Diagram of a 40 Gbps Polarization Division Multiplexed signal. I got this result from my simulation in OptiSystem.

I hope it helps.

Cheers,
Ahmad

Attachments:

1. 

   Eye-Diagram_40Gbps_Passband66GhzPDM.bmp
   

[Pelin Sule]

Thank you Ahmad.

from sunny but cloudy Turkey.

Pelin

[Jojo Mathew]

Hello Pelin Sule,
i have a very basic question… As we all know that Optical band has been divided in the form of windows. In other words first window , second window and third window… What is the reason for creating this bands in the form of windows rather than using the complete band as a single band.
Please reply the answer as early as possible so that i can continue with my project.
Regards.

[Dr. Dhiman Kakati]

Hi Jojo Mathew,

as per you have mentioned about the three windows in optical domain, they are experimentally found out from the optical fiber characteristics, such as attenuation, dispersion. The optical fiber posses lowest dispersion (dispersion is pulse broadening due to multi-path propagation ) at the wavelength of 1310 nm often called as zero dispersion window. at wavelength of 1550 nm the optical fiber posses lowest attenuation (around 0.16 dB/km) known as zero loss windows (attenuation is degradation in signal power due to propagation).

So basically all the three windows are made depending on the fiber characteristics.

Regards,
Dhiman

[burhan num mina llah]

Hi jojo mathew

In the 1970s, manufactures glass had a loss profile which showed a minimum loss at around wavelength of 800 nm (0.8μm). By the time this study of glass was going on, LASERs also were invented which used a semiconductor material named Gallium Arsenide (GaAs) for emission of light. GaAs intrinsically is capable of emitting light of wavelength 800nm. So, coincidently we had glass which had minimum loss at the wavelength that was emitted by LASERs, and so it proved to be great combination. So initial optical communications were started at 800nm wavelength region and hence it is called as the “First Window” of optical communication.
As technology improved, glass was further purified and it showed a region of minimum loss at 1300nm and 1550nm regions.
For further reference refer to following link.

http://nptel.ac.in/courses/117101002/downloads/Lec02.pdf

Regards

Burhan

[Bryan Tipper]

Please refrain from copying/pasting content from other web pages or articles.

Thanks,
Bryan

[FAYIQA NAQSHBANDI]

HELLO PELIN
In many, although not all, cases the output of a laser is polarized. This normally means a linear polarization state, where the electric field oscillates in a certain (stable) direction perpendicular to the propagation direction of the laser beam. There are cases (occurring e.g. with fiber lasers) where a different, e.g. elliptical but also more or less stable polarization state is generated, which can be transformed into a linearly polarized beam..This is not possible, however, for broadband emission with wavelength-dependent polarization state.
please refer to following link for further information.
https://www.rp-photonics.com/polarization_of_laser_emission.html
Thanks and regards

[Naazira Badar]

Hi Jojo..

Dhiman has rightly mentioned the favorable characteristics of the particular wavelengths and hence the windows these wavelengths belong.

Regards.

[varinder singh]

helo…jojo..
from point of view ,i think we requre polarization if we want to radiate wave….. the polarization of the wave will decide how much the your beam is stronger,,,and in which direction it will have the maximmun density
with regards

[Dr. Dhiman Kakati]

Hi varinder, I could not understand the above mentioned line that “we requre polarization if we want to radiate wave”, So willing to know what is the relation between Polarization and radiate wave.

Regards,
Dhiman

[Jojo Mathew]

Hello Varinder singh….thanks for your guidance…But as per my view,the strength of the radiation is not dependent ion the way it is polarized. The term polarization only reflects the way the radiations are radiated. As an example: Circular polarization radiates in all the directions that is Ubiquitous radiation…
Regards

[Ranjeet Kumar]

Hi Pelin,
Polarization in laser emission is important incase of nonlinear frequency conversion where phase matching in a nonlinear crystal is normally obtained only for one polarization direction.
It is also important in case where two laser beams have to be polarization-coupled.
And finally it is also helpful in the processing of laser beams in polarization-dependent devices, such as interferometers, semiconductor optical amplifiers, and optical modulators.
Although many fiber lasers do not generate a polarized output. This does not necessarily mean that the laser output is truly unpolarized, containing equal optical powers in two polarization components at any time, without any correlation of the corresponding amplitudes.

[Naazira Badar]

Hi all..
Ijust went throught the first comment here by Ahmad Mustafa. I think he has aptly mentioned the significance of polarization in optics. It is a characteristic property of light and significant as well.

Regards
Naazira Badar.

[Dr. Dhiman Kakati]

Hi Nazira Badar,
I want to add one more advantage regarding polarization is that we can split the polarization of the laser light suppose X and Y polarization and use each of them to modulate data separately, This will help you increase the data rate of the system up to two times, Here component splitter and polarization combiner are most useful. Thanking you.

Regards,
Dhiman

[Naazira Badar]

Yes, Dhiman Kakati.. You are absolutely right. Infact i have come across systems based on modulation based on polarization of light over the two axes. Thanks for elaborating on the discussion.

Best Wishes
Naazira Badar.

[Dr. Dhiman Kakati]

You are most welcome Naazira, please also refer to Varinder’s comment no 35478 he also has mentioned avery important point.

Regards,
Dhiman

[Naazira Badar]

Hi Dhiman, I checked that . Thanks a lot.

Thanks Varinder for adding to the discussion. (y)

Best Wishes
Naazira Badar.

[Dr. Dhiman Kakati]

You are most welcome Naazira, Feel free to ask any query here regarding Optisystema nd and other optiwave sodtwares.

Regards,
Dhiman

[SAHIL SINGH]

Hi all,

So nice to hear from all of you regarding the need for polarisation in laser optics… Thanks Dhiman for providing such valuable information on the aforementioned topic…

Regards
Sahil Singh

[Author]

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