Graduate Does the Silicon Nitride Waveguide Have a Cladding?

[Sciencestd]

Does the Silicon Nitride Waveguide (Si3N4) has a cladding ?! I read an article that they use the evanescent field of silicon-nitride waveguide.. If the answer yes it doesn't has a cladding then can I say that the evanescent field length in the surrounding medium is the mode field portion in that medium (outside the core)?!

 

[trurle]

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Does the Silicon Nitride Waveguide (Si3N4) has a cladding ?! I read an article that they use the evanescent field of silicon-nitride waveguide.. If the answer yes it doesn't has a cladding then can I say that the evanescent field length in the surrounding medium is the mode field portion in that medium (outside the core)?!

If the question is in context of on-chip optical waveguide, answer is "likely no cladding". Some processes have polyimide coating over top silicon nitride, but polyimide option is uncommon.

 

[Sciencestd]

Thank you so much for your answer. If we couple light into the waveguide... does the field above the surface then will be evanescent field or the mode field of the coupled light (let's say the mode field is Gaussian beam)..

 

[trurle]

Thank you so much for your answer. If we couple light into the waveguide... does the field above the surface then will be evanescent field or the mode field of the coupled light (let's say the mode field is Gaussian beam)..

Evanescent as long as beam angular diameter is much smaller than full reflection angle.

 

[Sciencestd]

Can you please explain it "Evanescent as long as beam angular diameter is much smaller than full reflection angle." Actually I'm not sure if I got it..!

 

[trurle]

Can you please explain it "Evanescent as long as beam angular diameter is much smaller than full reflection angle." Actually I'm not sure if I got it..!

Narrow beams will produce only evanescent field above waveguide; unfocused (i.e. on-chip LED) will produce propagation modes above waveguide.

 

[Sciencestd]

That's really great it's exactly solved my problem, Thank you sooo much :)