As being an amateur Quantum Optics researcher, I am looking for RG's help with comprehend a few questions re. my fiber Labs.
1. Assuming HeNe laser sources with LP and Random polarizations (RP), let such lights pass through aligned-fringe pattern interferometer (I had only done LP laser). Is there any difference in the TWO sources' output interference patterns? Why?
2. A LP free-space Laser source's MFD and waist get well aligned with a PM fiber coupler (slow axis is in vertical). How and why will the PM fiber coupling ratio (%) be varying with the different polarization incidence angles, e.g. Vertical, Horizontal and Diagonal?
What will be their output characteristics at the PM fiber output end in terms of polarization states?
3. To control a SM fiber output polarization, it can be done by using a fiber-stress type polarization controller. How if I can or cannot control a PM fiber output polarizations by using such controller?
4. How if a typical ED (Erbium-doped) fiber can be used as a CPA (coherent perfect absorber) for certain absorption Laser frequencies?
Or, if one can devise a ED fiber being the exact opposite of the laser process. In turn, make a design what we term a CPA. The ED fiber device perfectly absorbs incoming coherent laser light with given frequency and turns it into some form of internal energy — EM heat or energy.
that's a pretty long question!
interference between two sources is highly unlikely to happen, if it happens the interference pattern cannot be detected because of rapid fluctuations.
good luck for the other questions
Dear Dr. Hassan,
Thanks for your guidance and allow me to supplement my question 1. a bit more in below:
1. Assuming TWO HeNe laser sources one with LP and the other with Random polarizations (RP), l can see clear fringe pattern if LP light source pass through aligned-fringe pattern MZ interferometer (I had only a LP HeNe laser in my Lab). Is there any difference if take the temporal coherent RP Laser source for doing the same MZ test? Why?
I have just tested it in my Lab for my Question 3. and found a answer of mine.
I cannot control a PM fiber output polarizations by using such a pedal polarization controller, due to the PM fiber can maintain the LP input-to-output states at all time, even if I bend or twist the PM fiber with my hands.
Random polarization HeNe lasers usually also show a stable polarization direction but it is not specified which orientation it is towards the housing. Even when these lasers lack a Brewster plate there seems to be always a tiny unsymmetry that favors one polarization direction. But it might be, that neighboring longitudinal modes have perpendicular polarization orientation. Most HeNe lasers accomodate multiple longitudinal modes within the ~1.5GHz wide gain profile of the laser. Having modes with different polarization in your beam will definitely disturb your experiments.
Properly coupled light in a PM fiber cannot be manipulated with a "mickey mouse ear" polarization controller. These fibers are made to transport polarization undisturbed by stress onto the fiber. This is only true as long as the light is only coupled into one (the slow or fast) axis of the fiber. Each light component coupled into one axis will stay in that orientation towards the fiber axis. The phase relation between these two light components in both axes however is not defined at the fiber output. When there is an equal amount of light in both axes then any elliptical or oblique linear polarization state can be observed at the output.
(2) The coupling efficiency into a (PM) fiber should largely not change with changing polarization direction. It is at best a very tiny effect maybe when the fiber is cleaved under an angle then reflection differs for p and s polarization.
Alexander Dräbenstedt It looks great and thank you for sharing the best guidance with me.
I had ever made quite stable interference fringes by using randomly polarized incandescent light source (i.e. a flashlight as photo attached) along with Michelson interferometer as shown attached.
The light is not a "coherent" source at all. Still, it may show stable fringe patterns in my lab. It can be showing a clear momo-chromatic "Bull's Eye" fringes if I inserted a 633 or 532 nm bandpass filter before the screen.
The is why I wonder ... May someone help me to understand if a Randomly-Polarized coherent HeNe Laser source could make the stable and clear fringes along with MZ interferometer (I do not have that RP Laser in my lab).
The incandescent light source is not considered a coherent source.
This source has a very short coherence time, and you cannot consider it a thermal light though.
another how it could HeNe laser and randomly polarized at the same time!
honestly, I cannot see how could please explain how it is a laser system and randomly polarized.
if you are going to use a thermal light the fringes will be washed-out.