Laser experiment

[diachi]

“The energy of the individual photons does not matter, only the power matters, more specifically the power density. A red and a blue laser at the same power just emit different amounts of photons, the red emitting more. You can calculate the difference easily.
The distance will not make a difference, at the distances you'd need to see a difference you wouldn't be able to pop a balloon.
You need to take into account the beam specs, for this experiment to work each beam would need to have an identical divergence, geometry and power output. Assuming you'd see a difference in the first place. ”

I plan on keeping the power of the lasers, the beam profiles (power density), and the distances between the laser and the black balloon the same for all lasers. For my experiment, I am also assuming that the absorption spectrum of the black balloons are the same. Given that, I want to still experimentally see whether wavelength will affect the time it takes to pop the balloon.

I want to buy pre-assembled laser diodes with a lens, in a housing, with the driver attached. I am looking for three such assemblies: blue, green, and red. I want to find out what laser assemblies I can buy to carry out this experiment. Also, what should the wattage range be for the lasers to pop the balloons at a distance of around 2-5 meters?

Thank you for all your help!

That's going to be difficult, the three different lasers will have quite different beam specs. Getting them to be the same will require more optics than just a collimating lens.

Everything else being equal the wavelength won't make a difference. You're welcome to try for yourself of course...

 

[paul1598419]

laserstudent, I would pick a different laser project for your science project. You could get different wavelengths of lasers and show that their visibility is not linear. What I mean by this is the green laser looks brighter to our eyes than a red or blue one at equal powers. That is because the eyes see green more efficiently than red or blue. If you look at the visible spectrum and overlay the visibility at certain powers, they make a bell curve that peaks in daylight around 555nm. There is tons of information about this here and it is not something most people are aware of. It is also quite simple to setup and show. I'm assuming you are getting a grade for this. It is simple, not difficult to do and also informative.

 

[Cyparagon]

Are you suggesting... that this is a question that needs an answer?

No, this whole experimental premise is goofy. I'll try to get back to the point:

OP, the rate at which a balloon pops is entirely dependent on how much energy is absorbed. You cannot vary the energy by varying ONLY the color. If one pops faster, another variable is to blame. Probably the absorption spectrum of the target.

A blue photon does have more energy than a red photon, but if both outputs are the same, that means there will be MORE red photons than blue photons. Follow?

 

[Alaskan]

I'd look at these modules from Jordan's DTR LPF Google store, maybe he can adjust the outputs to match, but for popping balloons I'd use higher output diodes, these would likely need to be focused down to a point to pop balloons, if they even can then, depends on the balloon color. I've never used a laser to do so myself.

Due to likely differences of emitter size, let alone the optical effects from having long red to shorter blue wavelengths when using the same lens diameters, each of the outputs from these these diodes will have different characteristics, if so, you aren't going to produce identical beams at these three different wavelengths, at least, for infinity focus. They would need to be focused down to a spot as tiny as possible to get them to have closer power densities, but even then, they won't be the same. Again, the absorption will be different for different colored balloons, some balloon colors won't pop at lower power levels just due to a low absorption at a specific wavelength. A black balloon is what I'd use to help with that, but even then, unless close in focused to a tiny spot, 100 mw might not work at infinity focus, my guess is the power level is too low. Why did you choose 100 milliwatts? Has anyone here popped a balloon at 100 mw output power from a well collimated beam focused to infinity?

 

[Singlemode Laser]

laserstudent,

before a scientist designs an experiment he should make some basic assumptions and calculations. You assume that you will be able to keep all variables (beam profile, power, focus point etc.) constant except the wavelenght.

Then you state that the only thing that should makea a difference is the absorption in the atmosphere. Have you looked the order of magnitude for this effect?

If the absorption at 10m distance is 0.01% you have to control your experiment parameters at this level. Impossible if you not work in a top level laser lab, and even then.

A good lesson in a science class where laser light, high voltages etc. are present should be: Think first , do after.

Singlemode

 

[diachi]

laserstudent,

before a scientist designs an experiment he should make some basic assumptions and calculations. You assume that you will be able to keep all variables (beam profile, power, focus point etc.) constant except the wavelenght.

Then you state that the only thing that should makea a difference is the absorption in the atmosphere. Have you looked the order of magnitude for this effect?

If the absorption at 10m distance is 0.01% you have to control your experiment parameters at this level. Impossible if you not work in a top level laser lab, and even then.

A good lesson in a science class where laser light, high voltages etc. are present should be: Think first , do after.

Singlemode

Good advice! :beer:

 

[lazeristasUVISIR]

You need to take into account the beam specs, for this experiment to work each beam would need to have an identical divergence, geometry and power output.

For an "ideal" Gaussian beam it will be impossible to match both those parameters over the whole distance - the divergence is wavelength dependent
You'll need to choose the same divergence or the same beam spot size at a certain distance.

In a non ideal case more complications - M2, laser diode beam uniformity, multimode.

At least theoretically there are a lot of things to learn.

Experimentally a lot of things to solve - even creating (pumping) identical balloons.

Good luck!

 

[Alaskan]

I think he is stuck with loose approximations for this project.

 

[paul1598419]

Yes, he has a new thread asking for these lasers in the next couple of days and for $100 to $150. I tried to dissuade him from this project, but he seems intent on trying to go forward with it.

 

[laserstudent]

Thank you everyone for your feedback. Based on the information you all gave me, it seems that the project was much more complicated than I had initially imagined. So for now, I will take a pass on this particular project.

Thanks again!

 

[Alaskan]

Why do you insist on identical? The affect of wavelength can be demonstrated using beams which are loosely approximate to one another too, focus can adjust for some of the differences.

 

[lazeristasUVISIR]

Thank you everyone for your feedback. Based on the information you all gave me, it seems that the project was much more complicated than I had initially imagined. So for now, I will take a pass on this particular project.

Thanks again!

Don't worry. Your question/problem is a multi-$$$$ problem - military wants to get the same answer too. States and Soviets had big projects on developing lasers to shoot big boys balloons (rockets). Still the work is in progress. To me it looks that they went after energy than wavelength.