Simulating a laser focal point - any ideas?

I’m trying to simulate a laser beam waist (the part of the beam which is focused to a spot). I only know of one very good example of this rendered in 3D: - (the red object in the background)

Does anyone have any ideas how something similar could be done in blender?

In the past I have always represented this with a glass cylinder pinched in the middle and then played around a lot with textures & lighting but it never looks right, I’m sure there must be a way to do this with particle effects. Can anyone point me in the right direction?

(ps: I couldn’t find anything suitable in search or on tutorial sites; there are plenty of ‘laser beam’ tutorials out there, but most are unsuitable for this)