Have you considered some transparent cooling, f.e. liquid loop? I would be scared of bubbles but if you can sort it out - maybe that wouldnât be badâŚ
^ Yeah, i suggested that too, earlier.
Water.
Flowing on both sides of the Phosphor, sandwiched between thin glass or PMMA.
AR coated if thatâs worth it.
The Phosphor will have a really hard time getting hot with direct water cooling.
Water is great stuff. Itâs also as clear as water !
I donât think it will be close to 2000lm, maybe 500 or a bit more, apparently about half of the laser light doesnât enter the collimation lens.
Using some special combinations of lenses I could make 100% of it go to the 0.1mm spot on the phosphor but first I need to check that it wonât get damaged as it currently is.
Also, I already said this before, but water has a very low thermal conductivity.
Less than 1w/mk.
Just because it has a high heat capacity doesnât mean it will cool the object well, because the area is so small that the heat transfer to the water will be miniscule.
You need a material will high thermal conductivity to move the heat away, then have high surface area to transfer that heat to the water or air efficiently.
This is why CPU heatsinks and waterblocks use copper to move the heat to large areas of fins, which THEN are cooled by water or air.
You canât cool a computer by running water or air directly on the CPU.
You would get electrical issues when you do thatâŚ
But i see your point.
But water is of course much better than air.
I donât know. Maybe youâre right.
Itâs a âgut feelingâ i guess, that convinces / persuades me to believe a thin wafer of Phosphor, basically sitting in rushing water has a really hard time to get hot.
But since youâre planning on hitting only a 0.01mm² spot, iâm not so sureâŚ
Tell me if iâm boring you, but i had another thought:
Maybe place the Phosphor wafer in a ball bearing and spin it so that the laser point never hits a single spot for a long time.
You could add motion to the whole bearing so that it doesnât only hit the same circle on the Phosphor.
Yeah, a lot of hassle, i guessâŚ
If you want you can calculate what equilibrium temperature the crystal would reach if it was in water.
I can tell you right now that 18mm^2 of area will reach a very high temperature before 3W of heat are carried away by the waterâŚ
Also rotating phosphor is what many projectors use:
Doing this with a single crystal phosphor would cost tens of thousands of dollars, assuming you can get a piece that large.
Thanks
Iâm still waiting for more updates on yours!
You need to use two ar-coated (specifically for 450nm) cylinder optics together with a G7 focussing optic to get the best possible hotspot, highest efficiency and least amount of stray light. The cylinder lenses correct for the differently expanding axes of the rectangular laser beam. This can easily cost 100$, but itâs worth it.
The optical assembly and the cooling will probably give you the most grief.
Did you get a suitable, adjustable laser driver? I know a very compact one if you need it.
The engraving lasers they sell are doing .1mm^2 without any cylindrical optics, so Iâm going to try that first.
Thereâs no point in spending $450 on an acylindrical lens if Iâm already burning through the crystals without it.
The driver I bought can be regulated by 5v in addition to a current trim pot to adjust the maximum.
Also comes with a temp sensor for protection of the laser diode