7th Grade Science Fair Project

[Hemlock_Mike]

Dakota --

You are indeed a man of few words. I hope you enjoy our hobby and learn a great deal about lasers.

HMike

 

[jwc]

D{avid,akota}:

If you want to see what the crystals in a DPSS laser look like, here are a few shots I took of mine:
Crystal Tests and Module Characterization @ JWC.blog
More DIY Greenie Progress @ JWC.blog

Unlike most lasers, the two crystals in this set are not glued together, so you can see what they look like individually. Unfortunately, I can't take them out of their copper heatsinks to show you more.

In this picture:
http://jwcxz.com/projects/lasers/diygreen/pics/02-4.jpg
I use a set of crystals from a standard laser pointer to yield green from an IR input.

 

[Duster]

D{avid,akota}:

"Yes, I literally stuck a huge chunk of aluminum on the back of the LM317 because it was overheating and the output current was dropping."

How do you know it was getting hot? what are you using to measure heat? Is it because the current was dropping is how you could tell? I bet thats how, I may have just answered my own question! But you never know, thanks for the pics they are great! May Dakota use them (giving you credit of course) in his report?

 

[jwc]

Yes, when I noticed the current dropping I assumed that there was an overheating issue. My hand also accidentally brushed up against the IC and I burned myself too, so I knew it was time to find something to start sinking the heat. Interestingly enough, I was able to get that chunk of aluminum up to temperatures too hot to hold in a matter of 2 minutes with the LM317 on. I'm very surprised that I haven't killed the IC yet since it's only rated up to 1.5A (I need to buy its bigger brother, which can handle up to 5A).

Yes, Dakota is more than welcome to use those pictures or any pictures on my website for that matter.

 

[Duster]

I use a Temperature gun in my auto repair shop for various reasons. I wonder what it would read on the IC as it was heating up?, Like how fast the temp jumps and how the heat sink is able to dissipate the heat. that would be a cool test.

And thanks for the use of the pictures!

 

[Duster]

I wonder what would happen if you actually keep it at room temp during operation? or below? By surrounding it with a coolant? I have a small machine shop. I like things like this and work with some very small items. It would be a challenge if it would help. I looked up a LM317 and saw your pic of it. It could be done. I wonder if it was below temp, really below, if it would work better or does it have to be a certain temp to operate?

 

[Hemlock_Mike]

Dakota --- What are you running with the LM317 to get it so hot?
Remember (Vin - Vout) x current = power (heat) disipated. The device has a thermal roll back circuit for self protection.

HMike

 

[Duster]

Hi mike, that post you are talking about was a reply to JWC from me. We're still good. Nothing on our end getting to hot, YET! Dakota is not much for posting, funny he has a cell phone and is not into that to much either. Now his sister on the other hand......can text upside down, eye closed in a tornado! He worked on his report today, laser safety, things you can do with a laser etc. Yesterday he worked on What is a Laser, etc. Little bits at a time. Its all good.

 

[Duster]

This is Dakota's front page of his report he did a good job!

 

[Hemlock_Mike]

Dave ---

Looks good but how about letting Dakota post here..... Don't do so much that judges say that you did it all.

I liked the pix of him running the mill... When I was a kid, I had no tools because my dad thought them dangerous. You are teaching him well.

HMike

 

[Hemlock_Mike]

Duster and Dakota ---
The deleted posts don't look good. Are things going well?

HMike

 

[Duster]

Oh the Deleted posts.............Well that was us trying to figure out what we wanted our signature to look like. So those were our test runs. Sorry about that :yh:

 

[Duster]

Here is a copy of part of Dakotas report. It may have some bugs in it but he wrote it and I think he did a great job I posted some new pics of his project. We want to thank everyone for all there help. He will respond when he gets a break. Its been a long weekend finishing up the project display and writing the report. I am not sure when he will get a grade but when he does he will post it here. Thanks again.




What is a Laser?


Laser stands for Light Amplification by Stimulated Emission of Radiation.
A laser is a device that projects a highly concentrated narrow beam of light which is amplified to great brightness using stimulated radiation. Also know as DPSS stands for Diode-pumped Solid-State laser.

Lasers are commonly used for dental drills, laser-guided tools, laser pointers, CD players, DVD players, surgical procedures, bar code scanners and many other applications.

Basics of Lasers

What do atoms have to do with lasers? Atoms are the basic building blocks of all matter in this universe and are an essential part of how lasers work. The center of an atom is called the nucleus. The nucleus is composed of protons and neutrons.

Lasers are composed purely of photons, the basic unit of electromagnetic radiation and light. Photons are always in motion and travel at the constant speed of light.

Core Components of a Laser

The basic laser only needs three components to function. These principle components are an energy source commonly known as the pump source, the gain medium, and two or more mirrors that make up an optical resonator.

The pump source provides energy to the lasers system. This is the initial energy needed to excite the atoms within the gain medium.

The gain medium is the active laser medium or the source of atoms used to achieve stimulated emission and population inversion. This medium is the major determining factor for the laser’s operational wavelength, the lasers color.

The optical resonator, or optical cavity, in its simplest form is two parallel mirrors placed on opposing ends between the gain medium.


4


Simple Explanation:

The gain medium is built into the 808nm pump diode (pump source) and the Nd: YVO4 (crystal). The gain mediums in both cases are the same as the optical resonator. The semiconductor chip in the 808nm and the crystal make up the optical resonator and form two parallel mirrors placed on opposing ends between the gain mediums. The pump focusing lens and the expanding lens focuses the beam into the collimating lens producing a straight focused laser beam of photons.

 

[Hemlock_Mike]

Keep going guys --- There is a lot of difficult technology in that report but it is way above 7th grade level and farther above most teachers' knowledge. There is some stuff in there that you may need to sort out someday but there's time to do that as you learn.

HMike

 

[mrgoogfan]

This is the diagram we are using, it may not be the best we could be using.

HERE, i made you a drawing of a power regulated green DPSS laser. It is also a pdf vector drawing so you can make it as big as you want it w/o it getting pixelated.

[/IMG]

 

[Duster]

HERE, i made you a drawing of a power regulated green DPSS laser. It is also a pdf vector drawing so you can make it as big as you want it w/o it getting pixelated.

[/IMG]

Very cool drawing, thank you. This is the coolest forum. Things are looking good. As for his grade on his project, out of 100 points he received 110. His science teacher recommended he show it in the Sacramento Regional Science fair this year. I will update as things progress.