When do you need a laser diode driver to power and pulse a laser diode?
Is it related to the power it needs or the speed of the pulse?
I am looking to use multiple laser diodes which have an output power of 5mW, can this be done directly from a PCB circuit board. And I am wanting to pulse it at 1ns or faster.
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\$\begingroup\$ When you consider the non-linear lasing, and speed to prevent over voltage and thus over-current, then specs for turn on and turn off to or from a constant current maybe with optical and/or thermal feedback, now you have a design spec for a laser driver as opposed to a speaker driver. You must define all the specs. \$\endgroup\$– D.A.S.Commented May 25, 2019 at 16:11
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\$\begingroup\$ Closely related: 500mw laser diode: What's the point of a driver and will it need a lens to focus? \$\endgroup\$– The PhotonCommented May 25, 2019 at 16:15
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\$\begingroup\$ 1 nanoHenry and 10 picoFarad will ring at 1,200 MHz. You must control the dampening. Achieving, on a PCB, inductances as low as 1nH, is difficult. And using two "ICs", such as a fast transistor and a laser diode AND some PCB capacitance, is likely to be at the 10pF level. Thus 1uS edges are up against the wall. \$\endgroup\$– analogsystemsrfCommented May 25, 2019 at 18:22
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Some important features of many laser drivers:
- Constant current output
- Input voltage transient protection
- ESD protection
- Controlled turn-on ramp rate
Many will also have a control loop taking feedback from a monitor photodiode to provide constant optical power output rather than constant current output (which will result in varying output power over temperature and laser aging).
can this be done directly from a PCB circuit board.
Laser drivers are normally implemented on circuit boards, so yes.
And I am wanting to pulse it at 1ns or faster.
Pulsing a 5 mW laser at 1 ns is not an entirely simple problem to solve. You will need to carefully control the parasitics in the connection from your driver circuit to the laser to avoid ringing that could damage the laser.
You'll also have to account for the laser's internal capacitance, which will likely prevent switching it so quickly without at least using some kind of pulse shaping on the driver output.
answered May 25, 2019 at 16:20