What is nonlinear optics?

Question

Specifically, what are higher order effects in nonlinear optics?

Answer 1

Most commonly observed optical effects (refraction, diffraction, reflection) are linear: if you double the amount of light at the source, the results observed also double. Similarly for decreases in the amount of light. There is a linear relationship between source intensity and observed intensity as the light passes through the optics (lens, mirrors, etc.).

Non-linear optics don't behave that way at all. As the light intensity increases, the medium through which the light propagates (the optics) is stressed by the electrical or magnetic field (or both) of the light wave. This stress changes some physical property of the medium, such as its polarization or its refractive index, as a function of the light intensity. The result is a non-linear response of the material to the electromagnetic field of the light.

This can have some interesting consequences, such as the generation of harmonics of the original wavelength. It is this non-linear mechanism that allows a strong infrared, or near infrared, laser to be be frequency doubled or frequency tripled to produce coherent light at visible or ultraviolet wavelengths.

Answer 2

Scyth's answer is OK, but I don't know why light of different frequencies is important.

The superposition principle is the critical "linear" aspect of optics. Two sources of light add together "linearly" wavelength by wavelength. If we consider a laser as "one wavelength" which many are to a very good approximation, we expect that when we reflect it from a perfect mirror we will get the same wavelength back. A mirror which shifted the wavelength would be considered "non-linear."

As suggested above there are a great number of phenomena recognized and many more to be discovered. Often these effects are associated with interactions in solids, liquids or gasses that are enhanced by the excitation of the medium. This is often enhanced by the use of high powered laser systems.

Answer 3

Light normally obeys the superposition principle, in that light of different frequencies, when mixed together in some media, do not affect each other. This is the result expected from first order equations describing wave phenomenon, which assumes linear media. For non-linear media, however, such mixed frequency light can interact and produce secondary processes such as frequency doubling, parametric down conversion, parametric amplification, self-phase modulation, to cite a very few of a wide range of interesting optical consequences of such non-linearity. Non-linear optics greatly expands the scope of what can be done with light, it's a fecund field with many practical applications.

Answer 4

Scyth's answer is nice, yet i don't recognize why mild of diverse frequencies is significant. The superposition theory is the extreme "linear" element of optics. 2 sources of light upload at the same time "linearly" wavelength via wavelength. If we evaluate a laser as "one wavelength" which many are to an extremely good approximation, we predict that whilst we mirror it from a desirable mirror we are able to get the comparable wavelength back. A mirror which shifted the wavelength may be seen "non-linear." As pronounced above there are a great style of phenomena recognized and somewhat some extra to be stumbled on. many times those consequences are linked with interactions in solids, drinks or gasses that are greater via the excitation of the medium. that's many times greater via using extreme powered laser structures.

Answer 5

I think it had something to do with the solaar system.

Answer 6

I dont know