brillouin Definition and Topics - 6 Discussions

Brillouin scattering (also known as Brillouin light scattering or BLS), named after Léon Brillouin, refers to the interaction of light with the material waves in a medium. It is mediated by the refractive index dependence on the material properties of the medium; as described in optics, the index of refraction of a transparent material changes under deformation (compression-distension or shear-skewing).
The result of the interaction between the light-wave and the carrier-deformation wave is that a fraction of the transmitted light-wave changes its momentum (thus its frequency and energy) in preferential directions, as if by diffraction caused by an oscillating 3-dimensional diffraction grating.
If the medium is a solid crystal, a macromolecular chain condensate or a viscous liquid or gas, then the low frequency atomic-chain-deformation waves within the transmitting medium (not the transmitted electro-magnetic wave) in the carrier (represented as a quasiparticle) could be for example:

mass oscillation (acoustic) modes (called phonons);
charge displacement modes (in dielectrics, called polaritons);
magnetic spin oscillation modes (in magnetic materials, called magnons).

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  1. T

    Brillouin's negentropy in an Einstein solid

    Hello! I would like to apply Brillouin's negentropy principle to an isolated Einstein solid, with a decreasing number of oscillators. We assume that the number of oscillators are initially N and the energy quanta (q the number) remain constant. Firstly, I would like to know if this principle is...
  2. OrangeYogi

    What is the purpose of Electro-Optical Modulator (EOM)?

    Hello, I'm studying the setup of distributed Brillouin sensor (using fibre optics) and don't quite understand the purpose of EOM in the sensor. It says that "to generate both the pump and the probe waves from a single physical light source by using an electro-optical modulator (EOM)", but since...
  3. S

    Wannier functions integration

    Homework Statement I did not manage to get the final form of the equation. My prefactor in the final form always remain quadratic, whereas the solution shows that it is linear, Homework Equations w refers to wannier function, which relates to the Bloch function ##\mathbf{R}## is this case...
  4. U

    Energy gap between brillouin zones?

    Homework Statement Consider a monovalent 2D crystal with a rectangular lattice constants ##a## and ##b##. Find expressions for the fermi energy and fermi wavevector in 2D. Show that the fermi surface extends beyond first zone if ## 2a > b\pi##. If the crystal is now divalent, estimate the...
  5. U

    Volume of BCC and FCC?

    Taken from http://dao.mit.edu/8.231/BZandRL.pdf BCC In real space, it has a simple cubic lattice with one basis in the centre. Total number of atoms per unit cell = 2. Volume of primitive unit cell is then ##\frac{1}{2}a^3##. In reciprocal space, BCC becomes an FCC structure. It has a simple...
  6. C

    Dispersion relation for the free electron model

    I'm trying to get my head around what this means exactly. I've plotted the graph to help verse me with the functions that I've derived. From the free electron model, the wavefunctions are treated as planewaves of the form \psi_\mathbf{k}(\mathbf{r}) = e^{i\mathbf{k}\cdot\mathbf{r}} Due to...
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