Originally Posted by
RedlumX
The reasons why I think it is multiemitter are: the large power, the high asymmetry, the fact that at threshold once can see (when projecting on a screen) individual dots lighting up, which smear out when increasing the power.
On the other hand I checked by scanning the beam stripe over the slit of the OSA, that if there is "single mode", then the wavelength stays constant (up to the resolution which is a few Ghz). When the power is increased, then there is a transition to multimode and the mutual balance of the various peaks changes when scanning over the stripe (then also the interference pattern of the transverse modes blurs). So it seems that the "emitters" are locked to one wavelenghth at low power and at higher gain they unlock and at even higher gain the spectrum turns into a chaotic mess. The noise in the laser output grows accordingly.
It would be very interesting to settle this once for all. Probably this has a simple and well-known explanation by experts of diode lasers.... perhaps there are other constructions of diodes which have an extended size but are not multi-emitter in the classical sense.. I don't know.