I have this laser diode and instruction manuals tell me that even a short transient, 1ms long will destroy the diode if it exceeds a given voltage. I think the limit was 4.6V or somewhere around there.
How can I 100% make sure that voltage never exceeds some given level, not even for the briefest of moments? What component do I need to use?
Don't ever hook it to anything with a wire and you're still only 99% certain. All electrical components have a failure point. I was a test engineer for GE and did lightinging and static discharge testing. We never expected things to not fail, only to fail in a safe manner.