Frequency addition/substraction by mixing... for light !

[Externet]

Radio circuits widely employ mixers to obtain different frequencies.

 

Would the same happen with light ?

If am interested in producing 250nm (UV) light; can this be obtained by 'mixing'

400nm and 650nm light sources to obtain the difference ? (The 1050nm sum would also be there)

[Sensei]

Radio circuits widely employ mixers to obtain different frequencies.

Electronic circuit is modulating two or more alternating currents (AC) from two or more sine wave (or other wave) generators, typically. Prior sending them to transmitter.

It's very similar to ADSR sound generation (in keyboards for instance), where input sine wave is multiplied by couple linearly interpolated params.

It's completely different way of working than while summing frequencies/summing energies of photons at higher energies (in your example visible range spectrum).

 

 

Energy of photon is calculated using equation:

[math]E=h*f=\frac{h*c}{\lambda}[/math]

 

If you enter yours 400nm and 650nm in equation, you will get:

[math]E_1=\frac{h*c}{400nm}=3.1 eV[/math]

 

[math]E_2=\frac{h*c}{650nm}=1.9 eV[/math]

 

Add them

[math]E=E_1+E_2=3.1+1.9=5 eV[/math]

 

Reverse equation

[math]\lambda=\frac{h*c}{E}[/math]

and you will get maximum wavelength, corresponding to 5 eV energy, which is 247 nm.

 

400nm and 650nm light sources to obtain the difference ?

What you called "difference", in reality is summing energies of two photons. Exactly reverse.

 

There has to be carefully designed set up which absorbs two photons, and release one photon, which has energy equal to energies of two incoming photons.

 

Two-photon absorption

https://en.wikipedia.org/wiki/Two-photon_absorption

 

Second-harmonic generation

https://en.wikipedia.org/wiki/Second-harmonic_generation

 

Sum-frequency generation

https://en.wikipedia.org/wiki/Sum-frequency_generation

Edited February 11, 2016 by Sensei

[Externet]

Thank you, Sensei.

Are you saying that the sum of the energies of mixing 650nm light + 400nm light is nearly equal (247)
to the energy of a light with the difference of their wavelengths 650nm - 400nm = 250nm ?

Can the energies be substracted ; and what would that imply ?

 

minus = 1.2eV

 

 

Like in radiofrequencies, mixing say 1 MHz and 0.545 MHz yielding 1.545 MHz, and 0.455 MHz besides the fundamentals.

 

Your response says "It's completely different way of working than while summing frequencies/summing energies of photons..." , then substracting would be 'no'. Correct ?

 

 

What about ----> https://en.wikipedia.org/wiki/Subtractive_color

Is anything there related to this discussion ?

[swansont]

Thank you, Sensei.

 

Are you saying that the sum of the energies of mixing 650nm light + 400nm light is nearly equal (247)

to the energy of a light with the difference of their wavelengths 650nm - 400nm = 250nm ?

 

Can the energies be substracted ; and what would that imply ?

 

 

minus = 1.2eV

 

 

Like in radiofrequencies, mixing say 1 MHz and 0.545 MHz yielding 1.545 MHz, and 0.455 MHz besides the fundamentals.

 

Your response says "It's completely different way of working than while summing frequencies/summing energies of photons..." , then substracting would be 'no'. Correct ?

 

 

Not only can you add/subtract the energy, you have to. Wavelengths don't add, but energy has to be conserved. So you view this as frequency sums and differences, because those terms are proportional to the energy.

[Externet]

Thanks. OK. Wavelenghts do not add.

 

Let me translate all to frequencies...

 

Will mixing 460 THz with 750 THz produce 1210 THz and also 290 THz ?

[Klaynos]

It depends on the material (including it's crystal structure and orientation).

 

Have a look into the nonlinear generation in znte (optical rectification).

[swansont]

You should also realize that this is generally an inefficient process until you get to fairly high intensities.

[imatfaal]

You should also realize that this is generally an inefficient process until you get to fairly high intensities.

 

Pumping high intensity light into a crystal structure sounds a bit laser-ish - are there connexions?

[swansont]

Pumping high intensity light into a crystal structure sounds a bit laser-ish - are there connexions?

 

It's a nonlinear process; it varies as the square of the intensity. You want two photons around to interact, so the probability goes up with more photons around.

 

It's not like lasing because there is no gain - you don't end up with more light than you started with. No energy coming in from the medium being converted to photons. But it's under the same umbrella of photons interacting with matter.

[Klaynos]

It's a nonlinear process; it varies as the square of the intensity. You want two photons around to interact, so the probability goes up with more photons around.

 

When I used to utilise it we used a femptosecond laser to maximise the photon density in a reasonable spot size in the crystal. Tried to get right on the edge of where the crystal would burn.