Tutorial on Wave Optics

[Music] welcome to introduction to photonics so we've been talking about interference of light you know we've been treating light propagation in waves and we've been talking about recently we'd been talking about the statistical property of light which provides this concept of temporal coherence and spatial coherence and what we're going to do in today's session is

try to see if we can use the knowledge that we have gained so far see if we can use that to actually design certain optical components okay and one of those we started doing in the last session Orsino we said we'll consider interference in thin films right and while we are considering interference in

thin films we noticed that whenever light goes from one medium to another medium it's going to undergo certain reflection and we recognize that if you look at going from a rarer medium into a denser medium that is n 2 is greater than n 1 then you have a PI phase shift at that interface now based on this we

were asking the question whether it is possible to you know have things like anti-reflection coating so i mentioned that if you're going from air to glass let's say you have this air medium and going into a glass medium we expect to have a certain reflection at that interface and so if you are going in

from here you're going to have a reflection at that interface and that reflection is gonna give you a PI phase shift is there any possibility that you can cancel this reflection using the kind of properties that we have talked about okay this is the question and the answer turns out to be yes we can do

that provided you have destructive interference between the incident wave and the reflected components okay so what are the reflected components we are talking about now this incident wave suppose if it's incident before it hits the glass medium before it under before it hits that inter glass interface it encounters another medium let's say a