How to get unkown laser diode to operate

[AquaticHarpy]

Hi. I'm relatively new to lasers and have a few unknown diodes I'd like to test and figure out, they are 3 pin and I can't get one to fire with my lab bench. Any help is appreciated on how to get some light from one. Thanks!

 

[FireMyLaser]

I have few ways to guess what an unknown diode is capable of:

-What is the package type of the diode
-Markings on the diode
-What equipment the diode came from
-Use a power supply limited to 4V/10mA to find the pinout (limit to 2V if you know the diode is red or IR beforehand)
-Measure the forward voltage at 20mA to get a check on the impedance (don't let the diode heat up)
-Carefully adjust the current to its lasing threshold and take note of what that current is (don't let the diode heat up)
-Measure forward voltage again at threshold (don't let the diode heat up)
-Note the emitted color/wavelength of the diode
-Make effort to take accurate measurements

With this basic information one can guess what a safe operating current might be for the diode.

 

[AquaticHarpy]

I have few ways to guess what an unknown diode is capable of:

What is the package type of the diode
Markings on the diode
What equipment the diode came from
Use a powersupply limited to 4V/10mA to find the pinout
Measure the forward voltage at 20mA to get a check on the impedance (don't the the diode heat up)
Carefully adjust the current to its lasing threshold and take note of what that current is (don't the the diode heat up)
Measure forward voltage again at threshold (don't the the diode heat up)
Note the emitted color/wavelength of the diode

With this basic information one can guess what a safe operating current might be for the diode.

I have a variable lab power supply. How do I test pinout exactly?

 

[FireMyLaser]

By trial and error. You will get a faint glow from the diode when you find the correct pins. If it's IR then you need to look through a camera to see it. It is unlikely to lase or be dangerous at 10mA, but it should produce light.

 

[AquaticHarpy]

By trial and error. You will get a faint glow from the diode when you find the correct pins. If it's IR then you need to look though a camera to see it. It is unlikely to lase or be dangerous at 10mA, but it should produce light.

How fast will I kill it, what sort of draw should I look for in terms of voltage and amperage. I have 47 of these

 

[FireMyLaser]

If you do what I wrote in my first post then you wont kill it. I have no expectation of V/I and until you report back. If you have 47 identical diodes, you may just sacrifice one and turn up slowly until destruction, and take note of the current on the way (your call). The diode must be heatsinked.

 

[AquaticHarpy]

It's red. Very very very faint

 

[kecked]

Sounds like IR

 

[AquaticHarpy]

I had to look directly into the diode to see it. Probably not safe.. pulled .9ma@2v

 

[FireMyLaser]

Look through a phone camera and if it looks purple then it's IR.

 

[kecked]

rather foolish. Don’t repeat. iR can be watts and all you see is a tiny glow. At that current I doubt it was lasing.

 

[AquaticHarpy]

Yup! Thank you

 

[WizardG]

Don't let the faint appearance fool you. It might be 808nm infrared. Try using a digital camera and see if that doesn't 'see' the light from your diode better than your eyes do. If you carefully turn the current up (keep the diode heat sinked) you'll probably see the output very suddenly jump up. This is the lasing threshold: the point where the diode starts pumping out LASER light. NEVER EVER look straight into a powered laser diode.

 

[AquaticHarpy]

It goes from purple to deep red then dims out with wattage increase

 

[AquaticHarpy]

I've got no heatsink and it's in a plastic enclosure

 

[FireMyLaser]

Seems it is a fibre coupled IR diode. Perhapse for internet connection and low power.