Interaction of a phonon with evanescent wave

In summary: This can be seen in the experimental results where a large shift is observed. Further investigation and analysis may be needed to fully understand the underlying mechanisms.
  • #1
physicsninja
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When exciting a phonon mode with an evanescent wave possessing a wavevector ~100-200X larger than freespace but still ~10X smaller than fermi wavevector, would one expect a different resonance frequency for the phonon mode? I would think not.. but experiment seems to say yes.

More specifically: I am dealing with the main infrared active mode of SiO2 at 1080cm-1. I bring an evanescent probe near the surface which is capable of generating light of any frequency 900cm-1 to 1250cm-1 (enough to make a spectrum) with wavevector equal to roughly 1/probe radius ~ 1/10nm. This ends up being something like 100-200X larger than the free space wavevector. Experimentally I am seeing a large shift and I am not sure why.

Any ideas, thoughts or suggestions are welcome. Thanks!
 
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  • #2
Yes, it is possible to expect a different resonance frequency for the phonon mode when exciting it with an evanescent wave possessing a wavevector much larger than freespace. This is because the evanescent wave has different boundary conditions which can affect the resonance frequency of the phonon mode. The larger wavevector can also cause a shift in the resonance frequency due to the increased wave-matter interactions. In addition, the evanescent wave may interact differently with the material near the surface, leading to a different resonance frequency.
 

Related to Interaction of a phonon with evanescent wave

1. What is a phonon and how does it interact with an evanescent wave?

A phonon is a quantum of lattice vibration in a solid material. It interacts with an evanescent wave, which is a type of electromagnetic wave that decays exponentially as it propagates through a material. This interaction occurs when the phonon absorbs or scatters the energy of the evanescent wave.

2. What factors affect the strength of the interaction between a phonon and an evanescent wave?

The strength of the interaction depends on several factors, such as the frequency and intensity of the evanescent wave, the properties of the material (e.g. density, crystal structure), and the temperature of the material. Additionally, the angle of incidence and polarization of the evanescent wave can also affect the interaction.

3. How is the interaction of a phonon with an evanescent wave used in scientific research?

This interaction is commonly used in studies of surface vibrations and surface plasmons in materials. It can also be used to manipulate and control the properties of materials, such as altering their optical and thermal properties. Additionally, the interaction can provide insights into the phonon energy spectrum and the behavior of phonons in different materials.

4. Can the interaction of a phonon with an evanescent wave be observed experimentally?

Yes, the interaction can be observed using various experimental techniques such as Raman spectroscopy, infrared spectroscopy, and scanning probe microscopy. These techniques allow for the detection and measurement of changes in the energy, momentum, and other properties of the phonon and evanescent wave during their interaction.

5. Are there any potential applications of the interaction of a phonon with an evanescent wave?

Yes, this interaction has potential applications in fields such as optoelectronics, nanotechnology, and materials science. It can be used to design and control the properties of materials for various applications, such as sensors, energy harvesting, and data storage. Additionally, the interaction can also provide valuable information for understanding the behavior of materials at the nanoscale.

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