Waveguiding, Modes, Organic LEDs

[needhelp87]

Hi everyone,

I was wondering if someone could please explain to me the concept of
waveguiding, coupling/coupled, and guiding mode.

Here is an application of these terms:

The photons emitted in the active region of OLEDs are
coupled into three types of modes: direct transmission into
the air, the glass total internal reflection mode, and the highindex
~ITO/organic! guided mode. Assuming Lambertian
light sources, the fractions of energy in the three modes have
been estimated as 0.2, 0.3, and 0.5, respectively.2 A number
of methods have been suggested for increasing the output
coupling efficiency. For example, random textures or ordered
microlens arrays have been employed on the top surface of
the glass substrate in order to minimize total internal
reflection.3,4 The thickness of the ITO layer has also been
controlled in order to reduce the energy in the high-index
layer.5 An integrated classical and quantum-mechanical weak
microcavity theory has been proposed in order to calculate
the efficiencies of each mode for OLED layered structure.6

I don't really understand HOW a photonic crystal helps "waveguide" these modes OUT of the OLED? I appreciate your help. Thanks!

Source: pbg.kaist.ac.kr/pdf_text/yjlee03APL.pdf

 

[needhelp87]

^ Bump ^

Please, any help is appreciated. I have a presentation due in a couple of days.

Thanks.