I was unable to focus the 445nm to a pinpoint as small as the 405nm. If I had to estimate it would be 0.4 - 0.6mm 'dot' for the 445nm vs a 0.1 - 0.2mm pin for the 405nm. Let's run with that:

- 405nm dot has a surface area of about 0.13mm^2 (using 0.2mm diameter)
- 445nm dot has a surface area of about 0.79mm^2 (using 0.5mm diameter)
- Assume the 405nm (200mA) puts out at 225mW
- Assume the 445nm (700mA) puts out 500mW
- 405nm delivers 225mW/0.13mm^2 = 1730mW / mm^2
- 445nm delivers 500mW/0.79mm^2 = 633mW / mm^2

So unless I can get the dot size down with the better lens the 445nm will have a hard time competing with the 405nm. This is consistent with my observations on the CNC so far.

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ReplyDeleteHey, thanks for the laser theory post. How long are you continuously running your laser during a CNC operation, and does it maintain its ability to cut?

ReplyDeleteThere is something else to consider with the different wavelengths. The actual energy delivered. Violet lasers deliver more energy than blue for the same power. The calculations are pretty simple, but I will only post the results per photon:

ReplyDelete405nm 3.061338207067eV 4.904804504128E-19J

450nm 2.755204386360eV 4.414324053715E-19J

650nm 1.907449190557eV 3.056070498726E-19J

450nm = 1.444 times the energy of 650nm

405nm = 1.605 times the energy of 650nm, and 1.111 times the energy of 450nm

so assuming the same absorption, and beam diameter you get more bang out of the 405nm.