My curiosity sparked, I grabbed a phototransistor and my oscilloscope and sent the laser beam into the phototransistor to see if the laser is PWM or current controlled. Result: Both are PWM controlled at ~250 Hz. So, @CNC-Maker was right after all.
Here’s the 1.6W laser (Enclosure door open):
PWM frequency ~250 Hz.
For the 10W the phototransistor went quickly into saturation and I had to measure in the weaker side reflections of the beam, so the pulses look broader than they are, but the situation is clearly PWM:
The Counter got confused by the bad signal, saying 715 Hz, but if you look at the timebase it is clearly the same ~250 Hz.
I re-ran the grayscale-square from this post, and again the PWM pulses resolved into individual dots. A bit disappointing…
Still, firmware has improved since past then: Inline power control is clearly now in the firmware, and also the laser does not stop at power changes. That at least is a huge step forward!