physics

Nonlinear photonic crystal

Nonlinear photonic crystal is a physics topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Nonlinear photonic crystal rather than just read about it. In short: Nonlinear photonic crystals are usually used as quasi-phase-matching materials. They can be one-dimensional, two-dimensional or three-dimensional.

Key takeaways

Nonlinear photonic crystal belongs to physics; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Nonlinear photonic crystal to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Nonlinear photonic crystal from memory before moving on to harder problems.

Reference excerpt

Nonlinear photonic crystals are usually used as quasi-phase-matching materials. They can be one-dimensional, two-dimensional or three-dimensional.

Nonlinear Photonic Crystals Broadly speaking, nonlinear photonic crystals (PC) are periodic structures whose optical response depends on the intensity of the optical field that propagates into the crystal. An immediate consequence is that such structures have new optical properties with improved or new functionalities that cannot be obtained by using their linear counterpart, namely linear pPCs. One such example is optical tunability, that is, optical control of the response of devices based on PC. Although tunability of optical properties of photonic crystals can be achieved, for instance, by applying an electric field to an inverse opal PC infiltrated with nematic liquid crystal, by modulating the PC's index of refraction through the electro-optic effect induced by an external electric field, or through temperature-induced changes in the PC's index of refraction, high-speed operability desired for certain advanced optical communication systems can be obtained only if intrinsic optical nonlinearities in the PC material are employed. The reason for this is the ultra-fast response of certain nonlinear dielelectric materials to optical fields. In contrast to the now very extensive body of research in the properties and devices in linear photonic crystals, research into the theoretical and experimental behavior of these structures under conditions of intense optical fields, e.g. in the nonlinear regime, is still in its formative stages. The index of refraction of a nonlinear crystal changes in response to an applied electromagnetic field. Some of the characteristics of nonlinear crystals used to generate entangled photons include:

Nonlinearity: The refractive index of the crystal changes with the intensity of the incident light. This is known as the nonlinear optical response. Periodicity: The crystal has a regular, repeating structure. This is known as the lattice structure, which is responsible for the regular arrangement of the atoms in the crystal. Optical anisotropy: The crystal has different refractive indices along different crystallographic axes. Temperature and pressure sensitivity: The nonlinearity of the crystal can change with temperature and pressure, and thus the crystal should be kept in a stable temperature and pressure environment. High nonlinear coefficient: a large nonlinear coefficient is desirable, this allows generation a high number of entangled photons. High optical damage threshold: Crystal with high optical damage threshold can endure high intensity of the pumping beam. Transparency in the desired wavelength range: It is important for the crystal to be transparent in the wavelength range of the pump beam for efficient nonlinear interactions High optical quality and low absorption: The crystal should be high optical quality and low absorption to minimize loss of the pump beam and the generated entangled photons.

References

External links Nonlinear Photonic Crystals

Worked examples

Example 1 — a first encounter with Nonlinear photonic crystal

Start with the simplest possible case. Write down what Nonlinear photonic crystal claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In physics, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Nonlinear photonic crystal before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Nonlinear photonic crystal ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Nonlinear photonic crystal

In research: Nonlinear photonic crystal appears in physics research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Nonlinear photonic crystal in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Nonlinear photonic crystal is common in secondary-school and first-year university syllabi. It links to neighbouring topics Nonlinear optical materials, so understanding it makes those chapters shorter.
In everyday life: Look for Nonlinear photonic crystal outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Nonlinear photonic crystal in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Nonlinear photonic crystal means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Nonlinear photonic crystal out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Nonlinear photonic crystal in simple terms?

Nonlinear photonic crystals are usually used as quasi-phase-matching materials. They can be one-dimensional, two-dimensional or three-dimensional.

Why does Nonlinear photonic crystal matter?

Because it connects several physics ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Nonlinear photonic crystal?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Nonlinear photonic crystal.