# How to find the right material to change the wavelength of light?

1. Jan 8, 2012

### EvilLost

Hello all,

I'm working on a personal design problem and am stuck. I am trying to figure out "how to figure out" what material I would need. I hope that makes sense.

For example: I have light of 400nm and I want to change it to light of 500nm.

I figured I could just pass the light through a medium of appropriate material, but I'm not sure how to find what that material is! (My numbers are artifical because I need a general solution to this problem...that is I need to find out how to find out the material for each of many different wavelength->wavelength changes)

PLAN B: If I can not change the wavelength of light, I CAN purchase a source that can output the wavelenghts I need (but it is VERY expensive). Is it possible to buy the source and then increase the INTENSITY of the light without buying multiple sources? I'd be interested in methods to increase the amplitude of the wave OR increase the intensity (# of photos) WITHOUT buying additional UV light sources (if i can do so using a combination of 1 UV source + white/other lights thats oK)

EDIT: To clarify, I was under the impression that when white light "splits" by going through a prism, this is because the diff wavelengths travel at diff speeds through the medium. In other words, the "sum" of the light is being broken up but *no wavelengths are actually changing.* I figured in order to accomplish my goal of ACTUALLY changing the wavelength, I need to somehow keep the speed the same....? is this not an engineering/materials problem but a theoretical physics problem?

If wavelength= C / freq .... I guess what I need is a material that can pass light through it WITHOUT slowing it down, but instead by changing its frequency.... is such a product not in existance? or ....?

I don't know if I'm confused or if this just doesn't exist yet...

Any guidance is appreciated,

Thank you

Last edited: Jan 8, 2012
2. Jan 8, 2012

### Staff: Mentor

Can you say more about why you want to do this? I could be wrong, but I don't think there is a straightforward way of doing this. You might be able to find materials where the 400nm light caused an electron orbital transition that could in turn give you the lower-energy 500nm photon back out when the excited electron decayed, but there would have to be some other transition involved that got rid of the extra energy of the original photon.

3. Jan 8, 2012

### Dr Lots-o'watts

In the case of nanosecond (or less) pulses of laser, one can find crystals that create harmonics of the incident beam. http://en.wikipedia.org/wiki/Nonlinear_optics

And some pulsed laser systems have a wavelength that can be tuned within a certain range (again using nonlinear phenomena), but it certainly isn't straightforward.

But do let us know if you find what you are looking for, for light that is not pulsed laser.

4. Jan 9, 2012

### Topher925

I think you're getting optical filters confused with something else. There really isn't any way to continuously convert light from one wavelength to another other than using fluorescent materials. You can do it in pulses (which you can repeat at high frequencies) by sending light to a phosphor which is basically what laser pumping is. For example you can shoot a piece of ruby with a light pulse around 400nm and it will emit light of around 700nm for a brief period of time.

5. Jan 10, 2012

### Isaacsname

I'd like to take this opportunity to blurt out something stupid:

Why not just use color shading like you would for stage lights ?

http://rosco.com/us/technotes/filters/technote_1.cfm [Broken]

Last edited by a moderator: May 5, 2017
6. Jan 25, 2012

### ColinW

You can change the wavelength while it is passing through the material, but when it comes out again it will return to what it originally was. To change the wavelength in air you would need to change the energy of the photons, which is definitely not trivial!

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