In order to test the module, I found a nice strip of aluminium and bolted the module, driver and power supply to it. Note that the wiring from the rear of the module is very close to the mounting point - it would be nice if this had some sort of protective gland around it, and maybe exited more centrally.
The driver was then connected to the power supply and the power supply connected to the mains.
Measurement was via a Radiant LPM (Uncalibrated, just used as it came).
Much to my surprise, within a few seconds of applying mains power, the laser came on at full power - despite there being no modulation voltage applied. This was entirely due to my error - There is a small switch on the front of the board, allowing selection between 'TTL' and 'AS' (analogue) modulation
- I'd missed seeing the switch, and had the modulation cable plugged into the 'AS' socket but the switch in the 'TTL' position. Moving the modulation cable to the TTL socket, the laser behaved as expected - i.e. it stayed off with an applied voltage of 0V to 2.8 volts - once anything higher was applied, the laser came on at full power. Clearly, if TTL is selected on the switch, the TTL input must be clamped at 0V, not left floating...
Analogue modulation is nice and linear - (yes, I remembered to change the switch as well as swap modulation inputs!) - with the diode in LED mode until around 1.28 volts, at which point lasing commences. Here's a graph showing output power vs modulation voltage.
I've been measuring the power with the detector about 400 mm from the laser - moving it closer only seems to make a couple of mW difference. The maximum power reading seen was 966mW - if anyone in the Southampton area has a calibrated meter, it might be interesting to compare readings, but as far as I'm concerned, it's close enough to 1W as makes no real difference.
The diode module has a TEC cooling plate underneath it, sandwiched between the diode holder and the mounting plate. There is a thermistor inserted in the diode block. It's clear that the diode output is very dependent on temperature, as, with the modulation voltage held constantly at 5V, the output power reaches an initial peak and then slowly ramps down in small steps, sometimes climbing back a bit before dropping further. At the same time, the alloy plate to which the diode module was bolted started to get noticably warm, clearly from the hot side of the TEC cooler. If the laser is left at 0V modulation for a few minutes then everything cools down and max power is available again. This is unlikely to be a problem during shows, when the beam is being continually modulated, in which case the chassis, as a heat sink, should provide sufficient cooling, especially as my projector has a couple of fans already fitted - however, using heat transfer compound between the module base plate and the projector chassis will definitely be necessary.
Beam profile at 400mm from the aperture is approximately 2mm wide and 4mm high.
That's all for now, next I will be installing it in my projector and seeing how it performs doing graphics and beams. This will take me a few days, watch this space!