Rehabilitating a Leadlight 105? Help?

Greetings fellow laser enthusiasts!

An old Leadlight 105 of mine has recently gone to laser heaven in the form of a dying 808 nm pump diode. As far as I can tell nothing else is wrong with it and so I want to tap into the existing crystals and brass module by replacing the diode and circuitry. What I am wondering (and have searched the forums with no success) is what was the optical power rating on the original pump diode?

The diode looks like a 3.6 mm can which if I am not mistaken I will be able to replace with a spare 808 nm diode out of a Blu-Ray burner I have. I will probably replace the driver for it as well.
I found mention of someone actually replacing the original diode with a stronger one (on the order of 500 mW) but could not locate details on it.

Is there anyone that can point me in the right direction to pursue this idea?
I am missing usage of the modded 105. It has been a sweet little piece of work for some time now.

Thanks!

-Scott

DVD/Blu-Ray drives use a 780nm IR diode, so it wouldn't work. Stonetek.org sells 500mW 808nm 5.6mm diodes for sale for <$10 I believe.

Prototype said:

DVD/Blu-Ray drives use a 780nm IR diode, so it wouldn't work. Stonetek.org sells 500mW 808nm 5.6mm diodes for sale for <$10 I believe.

Click to expand...

Ah ok so I was off on the size AND the wavelength....nice . I just checked the diode again and verified that in accord with what you are saying here a 5.6mm is what's needed.

I will check the Stonetek site. That would be pretty awesome to be able to get a 500 mW diode at that price and use that. I understand that the power losses through the optics and crystals can be fairly significant so it will be interesting to see what green power will ultimately be reasonably achievable.

Thanks Prototype!

-Scott

Hmmm, well Stonetek appears to only have diodes up to 300 mW. Any other suggestions?

Thanks again,

-Scott

Well there's a bunch of cheap 1W 808nm diodes on ebay but the ones I looked at were 9mm. Might be able to make one work by machining out the hole or making an adapter, I'm not sure how the beam shape compares though.

Anything ~500mW or more usually has a multimode beam, and not a nice one like the 445s have either . A 300mW pump would get you 75mW or so I should think, if you're good at alignment and lucky you might be able to see 100mW out, but that's expecting 30% efficiency in a pen laser.

A 300mW pump should be sufficient if you are going for 5mW out. You could probably get as much as 20mW or so without too much difficulty. 75mW will probably not be feasible unless the crystals are a "freak" set.

I am not sure what the set-up for the pump + crystal assembly is (it's been a while since I've looked at the guts of a Leadlight 105) but IIRC, the crystals are pumped directly by the diode with no additional optics to collimate the IR beam.
This makes it a matter of seating the crystals as close as possible to the diode and then rotating the alignment for best power. An LPM helps.

Start off testing at low currents. Check that the beam is in TEM00. When you get a good profile and a bright spot, you can crank up the power on the driver. Check that it is stable. If not, reduce power and/or apply more heat-sinking mass.

And be careful with the 808 pump light!

Prototype said:

Anything ~500mW or more usually has a multimode beam, and not a nice one like the 445s have either . A 300mW pump would get you 75mW or so I should think, if you're good at alignment and lucky you might be able to see 100mW out, but that's expecting 30% efficiency in a pen laser.

Click to expand...

It looks like Stonetek might just be temporarily out of 500 mW diodes. For me the ideal situation at the prices offered there would be to purchase the 500 mW and the 300 mW diodes and experiment with both of them to test which best suits my liking.

james1095 said:

Well there's a bunch of cheap 1W 808nm diodes on ebay but the ones I looked at were 9mm. Might be able to make one work by machining out the hole or making an adapter, I'm not sure how the beam shape compares though.

Click to expand...

I'm trying to go K.I.S.S. on this. Although it would be cool to see what a 1 watt diode could do here, the effort to machine the module and risks of damaging the crystals (or to eyesight in the form of an overdriven IR filter) precludes my wanting to go such a route.

Thanks for the idea though.

RA_pierce said:

A 300mW pump should be sufficient if you are going for 5mW out. You could probably get as much as 20mW or so without too much difficulty. 75mW will probably not be feasible unless the crystals are a "freak" set.

I am not sure what the set-up for the pump + crystal assembly is (it's been a while since I've looked at the guts of a Leadlight 105) but IIRC, the crystals are pumped directly by the diode with no additional optics to collimate the IR beam.
This makes it a matter of seating the crystals as close as possible to the diode and then rotating the alignment for best power. An LPM helps.

Start off testing at low currents. Check that the beam is in TEM00. When you get a good profile and a bright spot, you can crank up the power on the driver. Check that it is stable. If not, reduce power and/or apply more heat-sinking mass.

And be careful with the 808 pump light!

Click to expand...

Thanks for the tips.

-Scott

Simply replacing the pump diode with another may or may not always work.

Although they may say that they are 808nm, they may be out as much as 10nm.

Although YVO4 isn't as picky as YAG when it comes to pump wavelength, it still does matter. It may mean that the diode won't work very efficiency, or won't work at all for pumping.

wannaburn was the first to report this with the cheap 808nms. If you want a diode for pumping, go for a known source where the diodes are actually within 2 or 3nm within spec.