Friday, April 29, 2011

405nm vs 445nm comparison

I've been a bit disappointed by the 445 nm diode so far. It's not really burning as well as the 405nm diode. So I decided to put down some estimates to see what is happening.

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.


  1. Hi!, Congratulation for your project, realy is very it inspiring the make one based in this information. I belive in the criativity yet more when it is shared like you did. Very thanks and one more time congratulation.

  2. Hey, 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?

  3. There 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:
    405nm 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.