Electromagnetic Optics

[Music] good morning and welcome to a new session on introduction to photonics so the next couple of lectures we're going to sort of switch tracks to a new module and before I do that I thought we should go back and review what we have seen so far so we started looking at the science

of light as far as this course is concerned from the perspective of ray optics where we look at propagation of light in terms of straight lines that we call as rays and then we said ok that is going to be limited in terms of its utility because light may be treated as waves in in which case you have phase

and you know wavelength that can be used to describe light and so we've been looking at wave optics and we are at a point where we are sort of at a crossroads between wave optics and actually treating light as you know particles in terms of photons I say that because as you know in the last few

lectures we've been looking at the concept of coherence of light and we defined what temporal coherence and spatial coherence means and that is to say in practical light sources there is a certain level of randomness associated with the propagation of light a certain level of randomness associated with the generation of light itself we will come

back and look at that in the next few weeks but as of now we are just characterizing light propagation and and we are saying that you know quantifying that randomness is what we are trying to do in terms of temporal coherence where we say okay light may actually be polychromatic may have multiple colors and because of that

you may not be able to get perfect correlation when you take one wavefront and interfere with another a delayed wavefront right that's what we've been seeing with the Michelson interferometer and of course we saw that we could define a coherence time and through that a coherence length and of course some of you that are taking this course here