BA review: The Spyder III Arctic Blue laser from Wicked Lasers

But the blue lasers… I’ve heard about them. The brightness of a laser depends mostly on the power used*. A typical red laser might have a power of about 5 milliWatts (5 mW). My green one has a power of roughly 160 mW, which is a lot more than the red one. The blue one, though, has a power of 1250 milliWatts, nearly 8 times that of the green one!
So yeah, I wanted to try one out.
…
* Color is the next biggest factor, since our eyes are much more sensitive to green light than blue, or even red. Beam focus is another factor, and so on.

(edit: post seems to have disappeared. Erased from existence, using far less than 1.21 GW. Here is a copy of it from an aggregator site)

Thoughts:

More than a Watt of laser power in a handheld device? Damn dangerous. I agree, this is almost like having a gun in terms of safety & handling issues. The potential damage that could occur through stupidity and carelessness is significant. It comes with safety goggles, which not everyone will use, and even if Luke is wearing his blast shield while he waves his light-saber around, what about everyone else? I see trouble a’brewing.

The BA (sort of) underplays the significance of color. Color, or more specifically, wavelength, is in fact a huge factor in how bright a laser appears. In the early days of green lasers being available, they used some shady advertising tricks to exploit this by telling you the green laser was as bright as a red laser of a certain power, typically 5 mW.  But in the fine print you found that the green laser had less than a milliWatt of actual output they were leveraging the fact that the sensitivity near 550 nm is more than five times the sensitivity out past 650 nm. So the BA has rigged the answer a little by using large difference in power. A green laser is going to look brighter than a red laser that has twice the power.

I suspect that one of the issues here is that the eye’s sensitivity is usually portrayed on a linear scale, like here (fig 154), which shows the photopic (light-adjusted) sensitivity ranging from 400 nm out to 700 nm, which is the usually-cited range. Notice that scotopic, or dark-adjusted vision really kills the sensitivity to the red, which is a killer in an optics lab using red lasers. Turning off the lights has a smaller effect in one’s ability to detect a spot because of the loss in sensitivity fighting the reduction in background.

But the effect isn’t best portrayed on a linear scale, because you can still detect photons beyond those boundaries, and the linear scale doesn’t give this impression. If you look at it on a log scale, you see that while the photopic vision has a shoulder near 700 nm, it doesn’t stay flat. You can see light out near 800 nm (we use a lot of 780 nm in the lab, for Rubidium, and you can see diffuse reflections from a few-mW source), but your eye is a million times less sensitive to it than to green light. Put another way, if you see even dim light in the near-infrared (NIR), it’s fairly powerful. I once saw a spot from a misaligned 852 nm laser (used for trapping Cesium), which was disconcerting, because it must have been really, really fracking powerful.

One might cut the BA some slack, because my examples aren’t laser pointers, and while he said lasers, he probably meant laser pointer and was thinking of only those wavelengths — color kind of restricting one to the 400nm-700 nm range — rather than what one might find in a lab. And they don’t make laser pointers in the IR, because what would be the point? Right? Well, not so fast. Green laser pointers are commonly made from pumped, frequency-doubled IR light, and this arrangement can let a lot of the IR through if there is no filter, and there may not be one. So you can get a blast of 808 nm light from the pump, and 1064 nm from the beam that doesn’t get doubled to 532 nm. While often the bright green light would trigger a blink to help save your eyes, it’s possible that it won’t, because light that has refracted or diffracted (phenomena which depend on wavelength) won’t line up anymore. You could potentially get an eyeful of IR, while the green spot doesn’t hit your eye. By the time you notice a problem, it will likely be because retinal damage has already been done.

So color is a big deal in how bright something appears. Let’s be careful out there.