Portable FAP Red

[Alaskan]

Good, glad to see you have it functioning. Thanks for the offer on the toys, but if everything works out well, I'm probably going to be in Afghanistan in about 10 days and can't use a laser there on a military base in a war zone.

 

[Hemlock_Mike]

I'm on a TI forum now asking for help on circuits to make the power module
more CC rather than CV. I Plan to graph temp vs time at 15, 20 25 and 30 Amps
for my "bed".
Your "toy" is a special sheet of paper !! I pray for your safe return.
HMike

I ran temp tests tonight. One minute runs starting at 66 Deg F. BORING.....
I ran it at 15, 20, 25 and 30 Amps and the "curves" are linear -- About 2 - 3 Deg / 10
seconds. At 15 Amps, it ended at 80 Deg F. AT 30 Amps, 86 Deg F ( a little over
spec limit). I'm happy with one minute but if the ambient temp starts at 75 Deg --
I'm screwed........ I'll call Coherent again for advice on spec temp limits.

 

[Alaskan]

Good, thank you for posting the info. I wonder if their temperature specs are for long life and running it hot, for the amount of time you will put on it, might not be so bad?

 

[Hemlock_Mike]

Chris -- I got an email from TI today about making this module CC and he mostly quoted the data sheet -- BUT he gave me a phone # !!!!
I will be coupling the fiber cable to the module next - ALL cleaned with that super methanol alcohol. I'm taking this a step at a time now.
My final project may be larger than I wanted....
HMike
This damn thing set fire to three pages of paper with a POP. I gotta be more careful .....

 

[Hemlock_Mike]

I connected the fiber cable tonight -- BOTH ends cleaned !!! That damn flimsy thing can slip from your fingers and drag 25 AMPS of photons across the back of your hand :-( that smarts and stinks. I cut my hand getting away !!!
The Coherent fiber cable coupled with the 25mm FL housing shows promise for focus. POW crap burns....
I called Coherent today and the 30 Deg C rating is for holding close control on the nM output. He said that 40 Deg C should be OK if wavelength isn't important.
The engineer at TI can't understand driving a diode bar with the power module. He wouldn't listen enough to be of much help. I had to keep telling him that I had explained stuff to him... Whatta waste of time.
HMike

 

[RedCowboy]

:tsk: You must be more careful than that, you could put a couple pieces of masking tape across the fiber like a sandwich to make a place to hold it. Safely away from your cleaned end of course.

 

[Hemlock_Mike]

RedC -- I will be building a better optic bench to hold lenses etc. This was a basic experiment to see if the fiber cable can take the power and smooth the 19 point beam. The power is controlled by a PB switch which kills the beam when I let go as I did.
It looks good so far. I just don't want to toast another FAP fiber face. I'm running at 25 amps and have limited the power module to 35 Amps. I don't want to go above 40..
So far, everything is remaining cool at the optic connections -- that's why I cleaned them. I even filled the small optic cavity with He. I was hoping NOT to achieve fusion temps!!!
HMike
Maybe more pix tomorrow

 

[RedCowboy]

QUOTE : The power is controlled by a PB switch which kills the beam when I let go as I did. : END QUOTE

Oh very good idea, I didn't know that, that is good thinking. :gj:

I am curious to see how well you can get the 19 emitter bundle to focus at medium distance, I have some 12 and 20 waters that I have done little more than test.

Just out of curiosity have you ever worked with that 100w coherent doughnut?

I have seen some at decent prices and 100 watts could keep me happy for a little while anyway, lol.

 

[Hemlock_Mike]

I'm not familiar with the "doughnut" 100 W ---WOW - I'll have to look into that. Doped fiber or disk?
I just turned it down to 15 amps (just above threshold) and it still burns (I had to put out a small fire!) but I'm using a non NIR coated 75mm FL lens - hand held. I want to get a tight beam at several feet and a nice beam at distance but it isn't too visible in open air. I have made expanders for other lasers but this is different. The fiber seems to homogenize the beam. Crazy stuff we do
sometimes.
HMike
$1200 for a doughnut?? Not for me......... Is that a pump diode system or a laser system with an output similar to a CO2?
What are you building?

 

[DashApple]

doughnut diodes are used for pumping rods and would be pretty useless outside of this setup

 

[Hemlock_Mike]

In a Galilean expander, the two plano lens surfaces are to face each other. That means that the concave expander surface faces the fiber. This could produce concentrated reflections, though limited, back to the fiber face with potential damage.
I called Edmonds and asked (axed) what happens if I reverse the expander lens and the poor devil was stumped. I want the plano toward the fiber. Comments or suggestions?
I am redesigning my expander for this.
HMike

 

[RedCowboy]

I'm sure you have already covered this, but just the shape of your fiber end, the way it's cut acts as a numeric aperture, well with 19 emitters I wonder how this will work? What kind of head are these meant to use?

 

[Hemlock_Mike]

RC-- I don't know but I'm using a Coherent fiber jumper about 7" long which smooths the beam and I can get a small spot with some crap lenses. I have some new lenses coming from Edmonds for a simple 2.2X expander. I use the jumper to protect the output of the FAP for now.
It is a Fiber optic jumper - with SMA connectors - 800 micron - AR coated and it works well to eliminate the 19 spots.
HMike

 

[Cyparagon]

...the concave expander surface faces the fiber. This could produce concentrated reflections, though limited, back to the fiber face with potential damage.

If you're using plain-ol-glass, reflection will be ~10%. If you're using something that has AR coating, reflection will typically be <2%. The reflected beam will not all be concentrated on the fiber unless the focal length is exactly half what the distance to the fiber output is. Realistically, the power increase at the fiber would be well under 1%, and would only lower slightly by flipping the lens around.

Don't worry about it.

 

[Hemlock_Mike]

Cy -- That's what I was thinking but I don't want to burn another :-(
HMike

 

[Hemlock_Mike]

I got my lenses from Anchor (Edmunds) and the 31 mm Dia lens measures 18.1 mm.....
I called them and was told that these experimenter lens specs can vary up to 10%.
They have nobody there who can use a caliper to find a correct sized lens. USAUSAUSA!
HMike
05/13 -- I ordered my NIR coated lenses from Thor tonight - A bit $$$ but less than Edmonds.