Glow in the Dark

Remember way back when I told you about fluorescence?  Well there is another funny phenomenon called phosphorescence, and it's the secret behind all of your glow-in-the-dark decorations and toys.  You probably even know a little about how they work. 

Think about it.  When you look at the object in the dark, is it always glowing?  Not if you didn't leave it in the lamplight before you turned off your lamp!  That's because you have to "charge" the phosphorescent material up like a battery.  This "charging" happens optically.  Light from your lamp hits the atoms in the material, the atoms become excited and reach what is called a "triplet state," where the upper state lifetime for the atom is quite long (minutes or hours).  There is a bit of quantum mechanics behind it all, but the previous description is just a fancy way of saying the atom is storing the energy for a while before letting it go. 

When many of the atoms are charged, and you turn off the light, some of the atoms start spitting out their energy in the form of light.  This continues to happen until all of the atoms have released their energy.

How does this relate to lasers?  Well a laser can be used to charge a phosphorescent material super fast, since the laser is so intense and blasts all of the atoms in the material to their triplet states.  Check out the video below to see this in action!

Lasers help to free you from your demons

You were a teenager!  You were young, irresponsible, and wanted something to show off.  Getting that tattoo was the natural thing to do!

But now you are getting tired of putting lotion on it, and the image is blurring, and you are afraid of what will happen when you get wrinkles.  Maybe you are becoming a different person, and that image of the devil just isn't you anymore.  Maybe "Jessica" dumped you, and you want to erase every memory of her.  Whatever the reason, you want your tattoo gone.  Well take a look at this video, where a man came to a similar realization and is using lasers to help him get rid of his demons [source].

Laser Powered Cars!

 Can you imagine that?  Well your cars may someday be driven by lasers!  ........... indirectly.

     A new application has been considered by the Argonne National Laboratory where lasers drill the wells to get to oil and natural gas.  Here's how this works:  A fiber optic cable sends high powered laser pulses (nearly as powerful as the Navy laser) down a shaft to blast away rock, and then the rock is carried to the surface (by using drilling fluids or another method).  As you can imagine, this takes a ton of energy, but it can actually be less expensive than current drilling methods.  Current methods already require a lot of energy, and drill bits need replacing every so often.  That isn't true for laser drills.

     The Argonne Laboratory is actually working with the Colorado School of Mines on this project.  Dr. Ramona Graves in the petroleum department at CSM is in charge of research concerning laser-rock interaction, which exactly relates to this project.  So there are definitely efforts to get this technology ready for use in the field.

What you can't see CAN hurt you... but can be pretty useful...

As I showed in my video blog in my last post, infrared light is invisible to the naked eye.  You can detect its presence with an infrared viewer or infrared camera, but not many people carry those around with them.  My green laser pointer emits infrared light in addition to the green light.  This can be dangerous because that infrared light adds to the power of the total beam, and it makes the beam more capable of causing eye injury.  That means the user has to be extra careful to not shine the laser toward people.

Infrared light isn't all bad though.  Many high powered lasers, like CO2 or Nd:YAG lasers, use infrared light (a lot of it) to cut through materials.  For CO2 lasers and Nd:YAG lasers, the output wavelength is 1064 nm, which happens to be the same wavelength of infrared light that my green laser pointer emits.  The Nd:YAG laser is used for 3D engraving.  Check out the video below to see how that works!

What else can infrared light be used for?  Here is a project for those do-it-yourself-ers out there!

*************** AS ALWAYS, SAFETY FIRST! ***************

You can order an infrared laser* or LED (or buy a green laser pointer like mine and block only the green) and shine it toward an IR photodiode.

So what?  What does this accomplish?

Well the photodiode will sense when the laser is shining on it AND WHEN IT ISN'T!  If an object or person passes through the laser, the photodiode will know!  People won't be able to see the beam or spot on the photodiode, so the system can be used for security purposes.  Ever see laser trip alarms in movies or video games?  This is how they would work!
 
*You could get away with a cheap red laser.  Check out this link that shows the steps for the DIY project.

Many garage doors have a system like this (probably using an infrared LED) to detect whether there is an object or person under the garage door as it closes.  You have probably seen this and may have, like me, had to jump over the beam while ducking your head if you want to close the door and get out at the same time!

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!

FOX catches on...

     It looks like a reporter at FOX News has stumbled on the story about the Navy laser project I have been posting about.  The FOX report includes some details about the Navy maritime laser demo, the free-electron laser project, and a rail gun project they are working on too.  On FOX Nation, they also show the maritime laser demo video I posted in Navy laser demo.

I actually noticed a problem in the FOX News article about the free-electron laser.  In the article, they say,

"Called the FEL -- for free-electron laser, which doesn't use a gain medium and is therefore more versatile -- it was tested in February consuming a blistering 500 kilovolts of energy, producing a supercharged electron beam that can burn through 20 feet of steel per second."

The problem is that they claim the laser produces a "supercharged electron beam" which is what burns "through 20 feet of steel per second."  If the reporter had researched free-electron lasers, he would have known that the laser does produce an electron beam, but the beam oscillates causing the emission of an intense beam of photons, or a laser beam.  It is the intense laser beam that does the burning, and not the electron beam.

     I believe this inaccurate reporting, even though it seems like a small detail, is due to the fact that the FOX reporter is most likely not a scientific journalist, and so he did not understand the science in the first place.  There is another possible reason for the misreporting; the reporter might have believed that readers would not understand the science, so he simplified the science to focus on the big picture.  However, scientific journalists are much rarer nowadays than previously, so the first hypothesis is likely the correct one.

     I am also interested in the rail gun report seen in the FOX article.  It appears the Navy does not believe the rail gun will be ready until 2025.  Yet, there have been references to rail gun technologies in older video games (Metal Gear Solid, in which the big bad machine is equipped with a rail gun) and movies (Transformers 2, in which the Navy takes down a giant machine on top of a pyramid with a shot from a rail gun).  Word gets around, I suppose.

Navy laser demo

     Remember that laser the Navy was working on?  The one that cut through ridiculous amounts of steel per second?  Well check out this video I found at geek.com.  It shows a lower powered prototype of what they are after.

The article at geek.com describes more about Star Wars efforts, the Navy laser, and the Boeing laser that I have been posting about.  Looks like someone else is interested in this stuff too!

There is also a 5 minute Navy PR video concerning the laser system in the following video, for anyone interested in the Navy laser defense systems.  The PR video explains the Navy's goals and has some nice footage of takedowns.