The equation for the beam width of the confocal cavity – where has it come from?
A. The cross-sectional beam profile in a cavity is actually a 2D Gaussian function and the quoted width is the value to which the intensity falls off to 1/e of its maximum value. There is quite a bit of maths in the derivation and I felt deriving the equation would not add to the understanding of the physics – it would just be a maths exercise. So just try to understand what the terms are and what they mean – don’t worry too much as you will not be asked to derive it, or get marks for remembering it. HOWEVER THERE ARE SOME IMPORTANT FUNDAMENTAL EQUATIONS THAT YOU WILL NEED TO REMEMBER THAT WE DID NOT DERIVE – YOU WERE TOLD ABOUT THE IMPORTANCE OF THESE DURING THE COURSE.
