So my colleague was off seeing a diamond nitrogen vacancies lab,
That seems like a lot of work/expense to find a non-ideal source, and we got to talking about photon statistics.
You've got Hanbury Brown, which I tried to measure once, but made an error in my set-up.. maybe again some day, but it's damn hard to see 'photon bunching'... (George thinks about a rubidium lamp, pin hole and single photon detector...? and various filters.)
Anyway I was thinking of non-ideal light sources, Non-ideal, but fundamental.. not just a noisy laser. (or clouds going in front of the sun.) There are these labs that use a moving diffusior and laser speckle pattern to make noise.. but it's sorta man made. (you can change the diffusor speed, which changes the noise spectrum, so at least it has a knob.)
I once looked at the noise of a diode laser right near threshold; it looked noisier, but it was dang tweaky to keep the laser 'near' ... some FB loop that looked at the noise?
Other ideas?
George H.