Is there any specific kind of applications in PCF with zero confinement in terahertz frequency range?
The confinement loss of a fiber structure directly depends on the imaginary part of the effective refractive index. When the imaginary part of the effective refractive index is zero, we can say that the confinement loss of is zero.
In order to obtain the imaginary part, we used to add 10% thick Perfectly matched layer (PML ) to the outer surface of PCF structure. But we could obtain a zero imaginary part for the fundamental like mode at that time.
My questions are
1) Is it possible?
2) If so what are the applications of such condition?
Okay, now I get it. A PCF fiber can have modes with zero or negligible confiniment loss and for this, it is enough to increase the number of layers of air-holes. This is not so special, since other losses still exist in the fiber, such as absorption, scattering, and loss in splicing regions.
Because it is so easy to obtain negligible confinement losses with PCF, nobody try to do deep study about this. Higher order modes usually have higher losses, but increasing the layers of air-holes them can also have negligible confinement losses
@Marcos A R Franco
Thank you so much for the answer.
Yes, it is easy to design a PCF structure for negligible confinement loss. But first time I got the zero confinement loss with PML layer. In fact, my expectation is to estimate the loss of that structure. But I do not know that is given zero value even with PML.
When you use a numerical approach to evaluate the confinement loss (from the imaginary part of effective index), the value can be so small that is lower than the numerical acuracy. When this accurs the software can make a truncation resulting zero in the imaginary part of effective index.
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