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How to test a laser diode ?

Dim

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Purchased from eBay Blue Laser Diode 1.6w blue beam 1600mW 445nm M140 A-TYPE UK 450NM . But it is not burning. Tried with 1.2 A – there is blue light coming from the laser, it focuses on some points, but nothing, it gets hot. Tried 2 types of lenses, see attachments.
Any way to test if the laser is ok ?
 

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paul1598419

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Where to start?! You likely destroyed the diode if it ever worked to begin with. You need a constant current driver to drive these diodes. I don't know what to say about the lens to have pictured. It may be acrylic, which would melt at these powers and needs to be in a housing to focus it properly anyway. The laser diode should be pressed into a module or heat sink which would allw you to use the lens for collimating the beam. There's more, but I'm done.
 

Dim

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The diode has metal housing and cooling. Initially @ 200 mA it was burning with the “big” lens @ about 2-3 cm, but very lightly. Then I made a constant current power supply (LM317) @ 1.2 A and the diode was not burning any more even @ 200 mA.
Question: How a person can be sure that this is actually 1.6W laser ?
 

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Nexgen

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The diode has metal housing and cooling. Initially @ 200 mA it was burning with the “big” lens @ about 2-3 cm, but very lightly. Then I made a constant current power supply (LM317) @ 1.2 A and the diode was not burning any more even @ 200 mA.
Question: How a person can be sure that this is actually 1.6W laser ?
You already killed it, it turned to LED mode.:can:

What power supply are you using?
 
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Alien Laser

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It gets very hot because its LED, you had to much V on the diode, the way diodes work the require a driver to provide A and regulate V, someone correct me if am wrong :D
what did you use to measure the driver are you correct you used a 1.2 A and what about the Voltage !
 

Dim

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@ 200 mA – used one Li-ion cell, about 3.7-3.8 V
@ 1.2 A – used 12V power supply with LM317 regulator, not sure what was the voltage on the diode, but the current had not raised above 1.2A.

Is there a way to check if it is turned to LED mode ?
 

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paul1598419

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Sure. It gets hot, but puts out very little light. The facet has been damaged by catastrophic optical damage by over driving it, and without the proper heat sink to pull the heat away from the diode.
 

Alien Laser

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Yeah its LED, the lens could also cause the laser to go LED what lens did you use that is 1 fat lens :D
 

WizardG

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@ AL, "It gets very hot because its LED, you had to much V on the diode, the way diodes work the require a driver to provide A and regulate V, someone correct me if am wrong "

You're wrong. A driver regulates current, not voltage.
 

paul1598419

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You would think so, right? But, I have gotten Chinese drivers that are nothing more than voltage regulators. It shows up easily on a dummy load. This is especially true of very cheap drivers.
 

deadshadow

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as everyone said the diode is dead,you should not try to make your own driver as even an overshoot on the start would kill the diode,there are tons of things that can go wrong on a laser build but we can't be sure what happend in your case.

about your 2nd question if it is a blue diode then yes its the right thing that you bought,low powered single mode blue diodes are more rare and expensive so no way to got something else.
 

Dim

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Would you recommend looking for other lenses ? The fat came with the diode, the slim with the housing.
Not so convinced that this was really 1.6W laser diode. The UK seller on eBay stopped selling those and seems moved the ads to another account.
Any reliable seller of working refurbished laser diodes for engraving purposes ?
 

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deadshadow

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Would you recommend looking for other lenses ? The fat came with the diode, the slim with the housing.
Not so convinced that this was really 1.6W laser diode. The UK seller on eBay stopped selling those and seems moved the ads to another account.
Any reliable seller of working refurbished laser diodes for engraving purposes ?
about the lens something like this will work better.
https://www.ebay.com/itm/405-G-2-G2-AR-coated-aspheric-glass-laser-lens-for-400nm-700nm-laser-diode/112396538111?hash=item1a2b5b10ff:g:UtkAAOSwCQZZDCYb

but in your case you need a new diode.
im prety sure the diode you recieved was correct A140 or M140 Atype as any lower single mode 445nm would instantly melt the wires of the emitter at 1.2A

if you make another try get a proper driver for your diode and heatsink both diode and driver well.
 

Shotgundrums

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I made a thread titled “in need of itty bitty driver.” And I showed one which is nothing more than a couple transistors, caps and resistors and a switch, from a pointer.... the APC types... would they be better suited for low power applications i.e. measuring or leveling tools, low power pointers, gun sights etc?...:beer:

You would think so, right? But, I have gotten Chinese drivers that are nothing more than voltage regulators. It shows up easily on a dummy load. This is especially true of very cheap drivers.
 

hakzaw1

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Many here kill new diodes by touching them w/o ESD precautions--or 'testing' them with things like a 9 v batt.. no no never do that.

Another 'diode killer' is trying to set they current w/o using a dummy load or proper heat sinking --no do no do.

Some time has passed since the OP -- these are no longer expensive diodes--they can be gotten in heat sink w/ leads or even drivers for plug n play. At that time ESD is no longer a concern.
 




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