Optics: Plane mirror cavity - collimated beams | MIT Video Demonstrations in Lasers and Optics

[@sadiqnawazkhan3333]

Thank you, very informative and simple

[@jesussaucedolopez540]

thank you !!!

[@mengding92]

I have a question. Based on Fox-Li's method, for plane mirror cavity, there is a fundamental mode related to the mirror size and cavity length. If I launch collimated light into a plane mirror cavity, what will be the mode excited in a plane mirror cavity?

[@nc-broadcast]

Thank you!

[@nathanclin70]

Why is there a line of dots in the first part of the demonstration? Is it like fringes?

[@subhabrataghosh3565]

i think we have to read the theory to understand the experiment

[@hyportnex3973]

The light beam runs back and forth between the two mirrors but a small fraction of each round trip leaks out at the output mirror and that leakage is projected onto the screen. When the the mirrors are aligned, ie. they are coaxial, then there is only one dot, otherwise the dots are projected off axis and get displaced horizontally by one additional off-axis angle for each round.

[@SiggiJacksn]

plane cavity means that you have two plane and parallel mirrors facing to each other (each has a reflectance of less than 1, so some light can enter and leave the cavity at all) if the mirrors are misaligned they are not parallel anymore and multiple reflections will spread out more and more, leading to several dots with equal spacing (due to the angle between the mirrors)