You have just entered a portal to the wonderful world of lasers. The content that follows can get a little complicated. There will be some technical terms that I will have to use throughout the posts. I will definitely make the science easy to understand (if not, then get on my back and I will make things clearer). I will also try to add some kind of entertaining element to the posts to keep things interesting.
I highly encourage you to comment on my posts. Criticism is very welcome... just try to leave out the ad hominems.
Monday, April 11, 2011
The secret behind green laser pointers -- VIDEO BLOG
I took a trip down to the laser lab to get the scoop on my green laser pointer. The following video documents my journey:
The take-home message? Just because you can't see the infrared doesn't mean it isn't there. It can burn your eyes just as much as the green can. Just keep that in mind if you get your hands on a cheap green laser pointer.
For your reference, here is a chart of the electromagnetic spectrum, which shows where visible light is, and where infrared light is in relation to each other.
The three spots we saw in the video were the separated colors of light from my laser pointer. The left spot was green (532 nm), the faint middle spot was near infrared from the pump (808 nm), and the right spot was the infrared (1064 nm) that gets frequency doubled to green. Here is the picture in the video showing the steps taken to produce the green light:
In the video, I refer to an "infrared camera," but the tool I use is actually called an infrared viewer. The combination of the viewer with my camera, though, does imitate an infrared camera! So my verbal mistake wasn't too far off. Also, the video alludes to a nonlinear crystal that converts infrared light into green light. This is a fancy way of saying that the atoms in the crystal absorb reddish-colored light and emit green-colored light. This happens through a nonlinear process, and needs to happen because there are cheap materials that naturally can be used to make an infrared laser. Only recently has there been success with true-green emitting materials, as I report in my 3OH!3 post. I discussed a little about nonlinear processes in Adding and Subtracting for those who want to learn more.
Take a look, and enjoy the cool things I demonstrate in the laser lab! And definitely ask me questions if you have any!
Wow, that is awesome, I had no idea that is why the laser pointers were so cheap. This is also kind of scary. Does this affect happen without using a prism? Or is it that without a prism the green and infrared are on top of each other? Anyways I will definitely be more careful with my laser pointers now. Great video!
The beam that comes out of the laser pointer has green AND infrared, on top of each other as you say. The prism causes the two "colors" to get redirected at different angles (think of sunlight getting split into the colors of the rainbow as it goes through a prism). I had to use the prism to show that there was more than just green coming out of the laser pointer. Otherwise, we would have had to use a spectrometer, which does the same splitting of the colors but with diffraction gratings instead of a prism.
As you say, the laser pointers are cheap because they don't have an IR filter, but also because they are not always reliable. The alignment of the optics inside the pointer sometimes get misaligned, and that ruins the brightness of the laser.
Definitely be careful with your green laser pointers because of the chance that there is significant infrared coming out as well. One thing you could do is buy an IR filter and manually install it on the end of your laser pointer, something I might end up doing.
Benito, I have to say that your video is awesome. I think you just might be the successor to Bill Nye! Anyway, I have a quick question as I bought a 150 mW green laser from China a couple years ago. I am sure that it also emits tons of infrared as well. My question is if you are trying to burn things, isn't the infrared a good thing? I mean it is providing more energy. Why exactly is infrared from the laser pointer a bad thing?
When you are trying to burn things, you definitely want the infrared coming out of the laser. That's just more photons that the target will absorb, so it's that much easier to fry the object!
My only issue with the infrared is that I use my green laser pointer for presentations sometimes. If I accidentally shine the laser toward the audience or in my own eyes (directly or through reflections) the presence of the infrared will increase the risk of damaging someone's eyes.
The application of the laser pretty much governs whether or not you want the infrared. You make a really good point, though, and my next post will go into more detail about infrared laser light.
Thanks Jen. That graphic took about as much time to make than the rest of the video. Kinda stupid, but I had to put it in there twice just because of that fact. :P
Wow, that is awesome, I had no idea that is why the laser pointers were so cheap. This is also kind of scary. Does this affect happen without using a prism? Or is it that without a prism the green and infrared are on top of each other? Anyways I will definitely be more careful with my laser pointers now. Great video!
ReplyDeleteThe beam that comes out of the laser pointer has green AND infrared, on top of each other as you say. The prism causes the two "colors" to get redirected at different angles (think of sunlight getting split into the colors of the rainbow as it goes through a prism). I had to use the prism to show that there was more than just green coming out of the laser pointer. Otherwise, we would have had to use a spectrometer, which does the same splitting of the colors but with diffraction gratings instead of a prism.
ReplyDeleteAs you say, the laser pointers are cheap because they don't have an IR filter, but also because they are not always reliable. The alignment of the optics inside the pointer sometimes get misaligned, and that ruins the brightness of the laser.
Definitely be careful with your green laser pointers because of the chance that there is significant infrared coming out as well. One thing you could do is buy an IR filter and manually install it on the end of your laser pointer, something I might end up doing.
Thanks for the comment, and good questions!
Benito, I have to say that your video is awesome. I think you just might be the successor to Bill Nye! Anyway, I have a quick question as I bought a 150 mW green laser from China a couple years ago. I am sure that it also emits tons of infrared as well. My question is if you are trying to burn things, isn't the infrared a good thing? I mean it is providing more energy. Why exactly is infrared from the laser pointer a bad thing?
ReplyDeleteWhen you are trying to burn things, you definitely want the infrared coming out of the laser. That's just more photons that the target will absorb, so it's that much easier to fry the object!
ReplyDeleteMy only issue with the infrared is that I use my green laser pointer for presentations sometimes. If I accidentally shine the laser toward the audience or in my own eyes (directly or through reflections) the presence of the infrared will increase the risk of damaging someone's eyes.
The application of the laser pretty much governs whether or not you want the infrared. You make a really good point, though, and my next post will go into more detail about infrared laser light.
This comment has been removed by a blog administrator.
ReplyDeleteThis is great, Ben. More proof that I need to better integrate video posts into the project next year. Especially like the concluding graphic.
ReplyDeleteThanks Jen. That graphic took about as much time to make than the rest of the video. Kinda stupid, but I had to put it in there twice just because of that fact. :P
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Green Lasers