laser diodes

[boyle m. owl]

I had been farting around with low power lasers off of amazon

then i went to digikey.

what does it mean if the laser diode is radial? Is it the polarity or
something else? Would something like this replace the need for a helium
laser tube in a home built CNC cutter?

assuming proper cooling and power.

https://www.digikey.com/en/products/detail/excelitas-technologies/TPG2EW1S09/13547973

[Phil Hobbs]

That's a pulsed laser intended for lidar use. I didn't read the
datasheet carefully, but at 85W peak and 3A/W, it'll be expecting pulses
10-50 ns wide and a few dozen amps tall, with a duty cycle small enough
to prevent that poor little plastic package from turning to lava. The
abs max table on page 2 shows a maximum pulse width of 100 ns with a
duty cycle of 0.1% at most.

It's actually 5 laser stripes wired in series, so it needs quite a bit
of drive voltage. The usual way to drive these sorts of things is to
use a flip-chip GaN FET to discharge a few-nF capacitor into it. The
cap starts out at ~50V and drops nearly to zero when you're done.

Getting the drive circuit right is hard, because when you're going from
zero to 30A in 10 nanoseconds, one nanohenry in series with the
source of the FET will drop 3V, comparable to the FET's gate drive
voltage. (A nanohenry is not a lot. An inch of wire is about 20 nH, so
you are not going to be using white solderless breadboards with this
laser.) ;)

'Radial' means that the leads stick out the same side, as opposed to
'axial', as in a regular through-hole resistor.

If you're not familiar with fast-pulse, high power electronics, I
suggest starting with tamer stuff and working up to lidar lasers once
you've done a few.

If you're going to be working with lasers over a couple of milliwatts,
spend a few bucks on the right set of laser goggles. It's amazingly
easy to lose an eye otherwise, even if you're careful--all it takes is a
momentary lapse of attention or an unexpected distraction when you're
aligning your setup.

Dialing back to the CNC laser cutter application, this is _not_ the
laser you want. I've never built a materials-handling laser system, so
I can't be too much more help there. Photonlexicon.com is a good place
to find folks who maybe can.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com