A What are the unusual absorption features observed in the EIT signal of 85Rb gas?

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The discussion focuses on an experiment involving electromagnetic induced transparency (EIT) in 85Rb gas, utilizing two light sources for probing and coupling, with a stable polarization spectrum. The experiment aims to establish a Lambda-type EIT configuration, with specific energy levels indicated for both light sources. The researcher observes unusual absorption features on either side of the EIT signal when coupling light is applied, compared to the signal without it. The inquiry seeks explanations for these abnormal absorptions and invites feedback or additional insights from the community. Overall, the experiment highlights the complexities of EIT in rubidium and the need for further analysis of the observed phenomena.
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recently,I am doing some experiments about electromagnetic induced transparency in the rubidium gas.Comparing the signal with pump light and no pump light, i noticed that there are two strange absorption in the situation of no pump light.
Hello,everyone!
Recently i am doing an experiments about electromagnetic induced transparency in 85rubidum gas.
I have two light source,which use the polarization spectrom frequncy stablizaiton technology to make them stable.One is used for probing light,and the other one is used for coupling light.I will show you the polarization spectrom of rubidium85 below.and this picture is from[1].In this picture,the coupling light is stabilized in Fg=3 -- Fe=2(in blue),and the probing light is scanned in Fg=2--Fe=2,3(in red) with triangular wave.
1658392336617.png

As you can see,I try to built an EIT configuration of Lambda-type.I will show you the energy level diagram for the D1 line of 85Rb.and in this picture,I point out the coupling light and the probing light.
1658393030096.png

Also,I will show you my optical system below
1658393288015.png

Then,I collect the signal from the detector in two situations.one situation is collecting the EIT signal with coupling light,and the other one is without coupling light.I notice that there are two strange absorption on both sides of EIT signal,and i don‘t know what it is.I will show you this signal below.
1658394271118.png


in this picture, the signal from detector without coupling light is in blue,and the signal with coupling light is in yellow.I also show the corresponding scanning polarization spectrom of 85Rb in Fg=2--Fe=2,3.
You can see from this picture,there are two abnormal absorption on both sides of EIT signal campared the signal without coupling light.can anybody tell me what it is?if you need any parameters like the width of these two signal,please don’t hesitate to contact me.or if you have some new thoughts about my experiment,please let me know.
Thank you all!
Hope you have a good day!

[1]Bin Wu,Yin Zhou,Kanxing Weng,et al.Modulation transpfer spetroscopy for D1 transition line of rubidium[J].Journal of the Optical Society of American B,2705-2710(2018)
 

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