Where to buy Diodes!

[JimBo]

Well I've had a look....

I can't see the fine wire, but it must be there.
I have metered the resistance of the diode and I get 12Mohm forward and o/c reverse so I guess it may be ok.
Does anybody know if them resistances sound right?, I did remove the protection diode before making the measurements so it is just the c-block that I have metered.

Jim

[The_Doctor]

I think you might have problems. First, try looking again, but don't touch it with anything at all for now, unless absolutely unavoidable!

Earlier I mentioned bright diffuse light. I meant it, blast it with light. You could get within a metre of a 400 W metal halide lamp and still not be able to see it well without a small microscope to help you. You need all the white light and magnifying power you can get, unless you have hardcore industrial lamps right next to you there is no such thing as too much.

That reading you got sounds bad. It sounds like almost open circuit to me. You need to use a diode test and make VERY sure that the voltage the meter puts on the test probes is not more than about 2.5 volts. If it is, you can destroy the diode by connecting the probes the wrong way round, even without the 'help' of a static charge. Resistance ranges on multimeters usually put 3V or more on the probes, which is BAD for laser diodes.

[JimBo]

Right, it looks like I do need a new diode.

Now what I need to know is, is the diode 50mW or something else?
Is the crystal an exact doubler, if so, I will need a 946nm diode.
The ones that I have seen on the Roithner web site are 975 +/-15, also the c-block diodes start at 300mW. The 50mW are cans.

If Junks is reading this thread, do you have any?

Jim

[stanwax]

Jim
the diode will not be 50mW it will be MUCH more.
The blue is DPSS just like green but it converts a diferent ND line. ie 946nm as opposed to 1064nm.
The reason they are so much more expensive than green - when the principle is just the same - is that the 946 line yeilds far less output than 1064 for a given input (ie is much weaker) and more difficult to susstain. Also the 1064 line needs to be surpressed so the coatings within the cavity will promote 946nm lasing but suppress 1064nm. Just to make blue even harder the temp of the crystals is much more sensitive when 946nm is lasing - i beleive in the order of 0.1 degree celcius out either way and you loose lasing - or at least it seriously affects the effeciency. (another reason why overall blue is not as stable as green and why TECs in the cavity are an essential not a luxury.
Bottom line is you need 808nm pump diode. and it will need to be pretty big at least 2W I would say probably 4W. The problem you have is that you don't know what the original was and I dare say CNI won't tell you. You may have to measure the current to the diode of the working head and make an educated guess on the output - but there is no linear scale that says 1W=1200mA 2W=2400mA.

Hope this helps and does not put you off.

Rob

[The_Doctor]

50 mW will be the laser's blue output. That C-block diode has to put out more, I suspect over 1 watt, maybe as many as 3. Blue is not as efficiently made as green is. Best thing to do is ask the maker what method they used to get blue output, I think there's more than one way. You're lucky in a way, that construction looks nice, it's actually user-servicable. I wish my LambdaPro greens were like that instead of having sealed cylinders that can't be accessed without severe risk of breakage.

[JimBo]

So what about ballpark prices for the c-block.

Jim

[The_Doctor]

No idea, you'll have to take chances on eBay for that. Put in a search for dpss -pointer laser diode and have it mail you for weeks or more. You'll find something good. Main problem is not being tempted to buy all the other goodies you'll see. Don't make the search too specific, that makes harder work for you, trying to find whatever you might have missed...

C-block diodes usually go for a lot less than the equivalent power in a can package, and you get higher power in C-blocks too. Cost isn't the main problem. Knowing the current your laser is supplying to the diode is, as stanwax says. Also, you might get a higher power diode than you need, if it works, and you can afford it, do it, it will last longer at the output you need to use. If you take this choice, DO NOT actually force that diode to do more just because it can!! Seriously, don't, unless you want to add a ruined cavity to your laser troubles. Just exploit the longer lifetime of under-running a brute diode, don't let it be a brute, because it will destroy stuff if you push it too hard. There's a good chance the maker was already pushing that cavity as hard as they could easily get away with, raw diode power was the least of the performance parameters they had to strive for, so when you get a diode, start with reduced drive current, and adjust carefully upward watching the output till your blue is back to 50 mW.

[stanwax]

Jim
as usual Junktronix has them
try item no. 120079104247
90 quid for 4W cmount 808nm and its SDL - top quality!

Rob

[JimBo]

So it will be a 808 that I need not a 946?

I've taken the block off and as expected there are no markings.

Jim

[stanwax]

Absolutely 120% certain its 808nm

Any more pix yet

Rob