Low Power Laser Diode

[WalkerAdi]

Hello all -

New here, please let me know if this is the wrong thread to post this in, I will happily delete and/or move it.

I am working on a project using a PLPT9 450LB laser diode. Safety issues for testing this laser while the rest of the system needs to be tested and verified makes this diode impractical to use/power outside of the controlled environment of the lab. I would like to find a drop in substitute laser diode (and driver) that has much lower optical power to get around this.

Ideally, I would like to use a laser diode that can be driven at < 1 mW. Making it much safer to use without eye protection. I am concerned that this may not be visible and realise this is also dependent on the wavelength. I am open to using alternate wavelengths/colours if that is what is available, though. Additionally, if there is a clever way to make a "safety lock" that allows the driver to be set to a different current set point?

I am having trouble finding something that matches the sizing of the PLPT9 450LB that is low enough power. Does anyone have suggestions for this?

Does anyone have experience driving the above diode to the point of being "safe"?

Thanks in advance!

 

[loreadarkshade]

Unfortunately, this 9mm diode has a very high lasing threshold, meaning its minimum lasing output is around 20-50mW
You will have to use a micro-controller to PWM the diode from 50mW down to 1-5mW.
Safety locks are definitely achievable through said micro-controller, for example the Anduril software in flashlight drivers.

 

[WalkerAdi]

Unfortunately, this 9mm diode has a very high lasing threshold, meaning its minimum lasing output is around 20-50mW
You will have to use a micro-controller to PWM the diode from 50mW down to 1-5mW.
Safety locks are definitely achievable through said micro-controller, for example the Anduril software in flashlight drivers.

Do you perhaps have a suggestion of an alternate diode I could use that a lower lasing threshold?

I appreciate the PWM suggestion, but have a concern. With regular LEDs, you can PWM to get what appears to be a dimmer light due to the duty cycle. My concern comes from my understanding that the LED is in fact running at the full brightness, albeit for a shorter duration and therefore not being continuous wave. Applying that to the laser diode is where I become concerned - a full brightness laser beam for a short duration to have lower continuous power output is still a full powered beam and would still have a higher peak output and therefore poses the same risks to our eyes. Is this a sound concern?

I will look into the software you mentioned, thank you.

 

[loreadarkshade]

Do you perhaps have a suggestion of an alternate diode I could use that a lower lasing threshold?

I appreciate the PWM suggestion, but have a concern. With regular LEDs, you can PWM to get what appears to be a dimmer light due to the duty cycle. My concern comes from my understanding that the LED is in fact running at the full brightness, albeit for a shorter duration and therefore not being continuous wave. Applying that to the laser diode is where I become concerned - a full brightness laser beam for a short duration to have lower continuous power output is still a full powered beam and would still have a higher peak output and therefore poses the same risks to our eyes. Is this a sound concern?

I will look into the software you mentioned, thank you.

I'm afraid I cannot answer that, what a very good question I hadn't thought of. I believe you might be right, PWM-ing a 50mW laser to average 5mW is probably unsafe! Good catch.

There are PLENTY of extremely cheap 5mW diodes out there, for example the Osram PLT5 450B, which is 100mW max, could easily be lased at 5mW no problem since its threshold current is 17mA

https://look.ams-osram.com/m/711b74151583f43/original/PLT5-450B.pdf

But it is 5.6mm package. 9mm package is generally for higher output diodes.