Received the second component of my future project

Interesting. :+1:

My imagination runs wild, but i have no data / specs…

Is the phosphor water resistant?
Thinking glass - water - Phosphor - water - glass sandwich, water pumped through the sandwich.
Because obviously the Phosphor will get crazy hot when you point a metal cutting laser at it… :wink:

I’ve been thinking about the ‘reflecting LEP’ too, with an extremely tiny parabola behind the Phosphor, a tiny dent in a aluminium (coated) heat sink.
The dent has to be filled with a piece of Phosphor.
I think it will produce horrible tint shift artefacts though…
Other than that, it’s so small, how are you gonna shape a 1 - 2 mm diameter parabola in a piece of metal, and coat it with PVD ?
Let alone put the right shape of Phosphor in there…

How thick is the Phosphor you bought?

Yeah it’s water resistant, it’s just a crystal.
Water would change the refractive index and would probably make focusing stuff problematic.
Also even though it has very high heat capacity the conductivity is not that high so the small area of the crystal wouldn’t dissipate much heat.

There have been experiments using liquid which has phosphor particles in it within a cooling loop so it’s cycling the phosphor through a radiator for cooling.

The phosphor plates are 0.25mm thick.

So is salt. :slight_smile:

You’ll get it focussed, i’m sure. :slight_smile:

Maybe i’m under- or overestimating something, but 0.25mm of anything sandwiched between running water will have a very hard time getting hot.
All will go dramatically wrong though, when the water reaches 100°C somehow…
Can’t imagine that happening with proper water flow though, but i could be wrong.
But water is an awesome cooling medium. Very high thermal capacity.
Oh, and it’s as clear as water, of course. :stuck_out_tongue:

Interesting idea.
You’ll need more Phosphor though…
But i guess powdered Phosphors, as used in LED dies are not that expensive.

One more question.
What diameter laser beam do you plan on hitting the Phosphor?
1.5 mm ? Less?

It will be concentrated, not sure how small I can go before burning the crystal but I’m gonna try .1mm square.

.1 mm² ?? :open_mouth:

0.1 x 0.1 mm
:slight_smile: :slight_smile: :slight_smile:

Wouldn't that be 0.01 mm²?

yeah, a square with side length .1mm.

0.01 mm² ??

Wowzers…
Well, you can burn quite a few 0.1 mm² holes in a 9 mm² Phosphor…

Haha true :stuck_out_tongue:

Hmm…2000 lm from 0.01 mm²?
That’s over 60 000 cd/mm², nearly 160 times brighter than the current LEPs used in flashlights.

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 wouldn’t be bad…

^ Yeah, i suggested that too, earlier.
Water.
Flowing on both sides of the Phosphor, sandwiched between thin glass or PMMA.
AR coated if that’s worth it.
The Phosphor will have a really hard time getting hot with direct water cooling.
Water is great stuff. It’s also as clear as water ! :stuck_out_tongue:

I don’t think it will be close to 2000lm, maybe 500 or a bit more, apparently about half of the laser light doesn’t 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 won’t 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 doesn’t 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 can’t cool a computer by running water or air directly on the CPU.

You would get electrical issues when you do that… :stuck_out_tongue:
But i see your point.
But water is of course much better than air.
I don’t know. Maybe you’re right.
It’s a ‘gut feeling’ 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 you’re planning on hitting only a 0.01mm² spot, i’m not so sure…

Tell me if i’m 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 doesn’t only hit the same circle on the Phosphor.
Yeah, a lot of hassle, i guess…

Looking forward to this one! Fresh tech and new implementation, is always exciting.


I also need to correct The Driver, the BFF is definitely not 250Mcd. There is a reason I have said it start with a 1.

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 water…

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 :stuck_out_tongue:
I’m still waiting for more updates on yours!

Suggestion, wear an eyepatch over your best eye whilst working on this. And please don’t shine it in my direction.

No worries, update is coming, just been busy with some other stuff.

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 it’s 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.