Today, I was trying to achieve square beam and then to focus that beam with AixiZ lens.
When flat side of cylinder lens is facing chip of the diode it's impossible to get square beam.
After I managed to get something that looks like square I tried to focus light with AixiZ lens but beam looked like line, not dot.
Then I tried to face cylindrical side of lens to chip of the diode and then I managed to get very clear square.
But it's very difficult to do without precise lens holders....these holder should be adjustable so I can move lens from diode very, very precisely.
But I don't have that tool and don't have access to CNC machine.
After I managed to get the most symmetrical rectangle I again used AixiZ lens to get the smallest spot, but spot was very big and there were wings around dot.
I don't plan to use this laser for high distances so I tried to focus it to 15 cm but then only that I can get is very thin line and then I can not burn.
Here is video that shows everything:
YouTube - Problem with cylinder lens and 9mm 808nm diode
Maybe that lens is not good for these diodes or I just can not get very good square without precise lens holders.
After unsuccessful testing of cylinder lens I tried to find any other optics that can solve my problem.
Then I found very thick glass lens with very long focal point.
Here is picture of this lens:
I tried to put this lens just on the window of the diode and then to use AixiZ lens to focus beam to smallest spot at about 15cm.
And it worked...I achieved very small spot (looks like very small line) and laser can burn very well.
Laser burns better if I use that thick glass lens because all light is collected.
With only AixiZ lens some light don't pass lens.
But I don't know if this lens is optimized for 808nm wavelength and don't know how much power I lose if light goes trough this lens.
I don't have LPM to test it.
After all I'm very confused.
Should I try something else with cylinder lens, or to use that lens that I found, or to find other solution?