Understanding Optical Modes Without the Jargon

[Eriance]

What is an "Optical Mode".

I've been reading a lot of solar cell articles, especially those having to do with nanophotonics. There is a term that I keep running into, 'optical mode', but I've yet to find an explanation that I can visualize or understand. What exactly is the "mode" being used here? I know it ha to due with confining light to a certain area withing a optical waveguide, but I'm not sure what a mode is. Can someone explain in layman's terms what it is?

 

[Jano L.]

"Mode" refers to "abstract harmonic oscillator describing standing wave". For example, the EM field within metallic cavity can sometimes oscillate in such a way that the electric field at any place oscillates in phase with one common variable $y$ which varies sinusoidally in time.

There are many possible standing wave patterns, and each corresponds to one distinct "mode". This pattern can be complicated, with various nodal surfaces and variation of the maximum amplitude all over the cavity, but the temporal variation is a simple harmonic oscillation with frequency determined by the pattern. The more the number of nodal planes the higher the frequency of the "mode".

 

[Bill_K]

From the book "Nanophotonics",

Optical modes are the eigensolutions of Maxwell Equations which correspond
to a spatial distribution of the electromagnetic field which is stationary in the time
scale.