Laser diode pin configuration - Page 1
Forum section: electronics / projects

author: decoevvblog
author_rank: Newbie
timestamp: May 26, 2023, 06:15:00 am
content: Hi,I have this diode laser with photodiode...having these measures:the pin configuration should be like this, right??

author: PartialDischarge
author_rank: Super Contributor
timestamp: May 26, 2023, 06:44:37 am
content: The bottom multimeter should be connected in the uA mode

author: decoevvblog
author_rank: Newbie
timestamp: May 26, 2023, 06:49:46 am
content: ok but is this the configuration?

author: jonpaul
author_rank: Super Contributor
timestamp: May 26, 2023, 06:54:56 am
content: beware the laser diode is very suseptible to ESD, even nanoseconds of overvoltage can ruin the laser.The professional laser diode drivers have protecxtion, any DIY driver is risky.Suggest to keep part in foil wrap or short all leads with bare wire till innstalled in cktJon

author: decoevvblog
author_rank: Newbie
timestamp: May 26, 2023, 06:57:14 am
content: but is this the configuration?

author: PartialDischarge
author_rank: Super Contributor
timestamp: May 26, 2023, 07:07:24 am
content: The configuration for what? That circuit does nothing, it does not power the laser or measure the photodiode. You should learn first about laser drivers

author: decoevvblog
author_rank: Newbie
timestamp: May 26, 2023, 07:11:04 am
content: Quote from: PartialDischarge on May 26, 2023, 06:44:37 amBoth multimeters are set to measure Diodes..however I put the botton multimeter in µAdc, as suggested, but it shows 0µAdc...

author: decoevvblog
author_rank: Newbie
timestamp: May 26, 2023, 07:22:11 am
content: Quote from: PartialDischarge on May 26, 2023, 07:07:24 amfor now I want to understandthe pin configurationof this laser diode that I have, since I don't have the datasheet...

author: ajb
author_rank: Super Contributor
timestamp: May 26, 2023, 05:51:56 pm
content: The way the photodiode and laser diode are connected depends on the specific part you have. In some cases, the fabrication of the diode itself (meaning the actual semiconductor chip inside the can) affects how it can be mounted and bonded out, in other cases it's up to whatever the manufacturer chose. Sometimes you'll even see the same laser diode available in multiple pinout options, so it really depends on the specific part you have. Do you have a part number? Or at least nominal wavelength/power?Does the picture show your actual measurements in diode mode? 1.6V would be consistent with the Vf of an IR laser diode, or maybe a visible red, so it could be that you have the LD correct. I would expect to see <1V for the photodiode when forward biased, so I would guess that the photodiode is reversed from your diagram. But it could be that the 1.6V you're measuring between pins 2 and 3 is actually from a protection device in parallel with the LD--many laser diodes have an absolute max reverse voltage rating equal or less than their forward operating voltage, and some copackage protection devices. It could also be that there is no photodiode, not all laser diodes have them, even when they're in 3-pin packages.If the laser diode is a visible wavelength, you might be able to apply a very small amount of current to what you think is the laser diode and look for the subthreshold glow--but you have to be very careful about how you do this. Both for laser safety reasons, and also because you need to limit the voltage and current very carefully to avoid damaging the diode. I would probably use a reliable bench supply set to a fixed voltage below the diode's reverse voltage rating, and connect the laser diode through a fixed resistor and a potentiometer--the fixed resistor should be set to limit the maximum current to ~1mA or so when the potentiometer is set to its minimum resistance. If it's hooked up right, you should be able to get a faint glow even at very low currents and at voltages below the nominal Vf, much like an LED (laser diodes have a threshold current where they start to actually lase, below that level they emit only incoherent light basically operate like shitty expensive LEDs).Quote from: decoevvblog on May 26, 2023, 07:11:04 amYou won't read much from the photodiode without it being illuminated/biased correctly, so that doesn't tell us much.