Page 349 - Mike Murphy's Blog Posts

Then you plot the calculated fluences (energy densities) against the input setting, from your laser (as in the above graph).
This is then your calibration chart!
To find any output fluence you simply look along the x-axis - which corresponds to the 'energy' setting on your laser screen - and look up till you meet a curve - either 532nm or 1064 nm (for an Nd:YAG laser) - and then read off the corresponding fluence on the y-axis.
So now the numbers on your laser screen make sense - real fluences!
I tend to stay below 6 J/cm^2 for tattoo treatments (until you are tackling the real deep pigment when you will need higher fluences). Hence the green dotted line on the above chart - everything below that line is in the 'Safe Zone'. In other words, in this example, the laser can be set up to around 1300 mJ, and you know you are operating safely.
Note that this chart was constructed on the 1st July 2020 - calibration charts are time- dependent! Since the flashlamp will degrade with time, you really should get your system re-calibrated after around 150,000 shot (or so). These curves will 'drop' with time.
You should also note that the 532nm output is really a mixture of 532nm and 1064nm since frequency-doubling crystals are not 100% efficient. Typically, this can be in the ratio of 70% 532nm to 30% 1064nm.
Calibration charts are important since they tell you what your real laser outputs are. The 'mJ' numbers on your screen are quite meaningless! Unless you measure the actual output and its corresponding spot diameter, you cannot know the real numbers.
Hope this helps, Mike
Mike’s Blog Posts 349