Trying to work out correct current for driver...

[nzoomed]

This looks like what im after?

Astral SuperDrive V - 5A Adjustable Buck / Constant Current Driver w/ 1 kHz PWM | eBay

Astral SuperDrive V. PWM Frequency: 1kHz. Mode: Buck Driver (step-down). Ripple: Depends on ratio of V-out / V-in. At 5A and 4.5Vf output, ripple is about 1-2%. V-out (V): 2.5 - 13V (depends on current output and laser diode’s Vf).

www.ebay.com

 

[paul1598419]

An M140 diode has a forward voltage ~4.5 volts. At 1.8 amps it consumes 8.1 watts of power to give 2 watts of optical power out. That means 6 watts is dissipated as heat for just 2 watts of optical power out. The driver also consumes power and much of that is wasted as heat. Heat is a real part of laser diodes and the reason they need substantial heat sinking to keep them from thermal runaway and failure.

I don't believe the astral buck driver is still available. Oh, I see Barnett has some still for sale. Pradipta, the engineer who developed and built these drivers, is not around much lately.

 

[nzoomed]

An M140 diode has a forward voltage ~4.5 volts. At 1.8 amps it consumes 8.1 watts of power to give 2 watts of optical power out. That means 6 watts is dissipated as heat for just 2 watts of optical power out. The driver also consumes power and much of that is wasted as heat. Heat is a real part of laser diodes and the reason they need substantial heat sinking to keep them from thermal runaway and failure.

I don't believe the astral buck driver is still available. Oh, I see Barnett has some still for sale. Pradipta, the engineer who developed and built these drivers, is not around much lately.

OK, sweet, so at least I know the astral driver is OK.
There were some other buck drivers I had seen from a US seller but not showing any more on ebay.