Nano-Optics Flashcards
How do we treat free electrons in a metal?
plasma (highly ionised gas)
What kind of motion do we see for electrons in a metal when a field is applied?
oscillatory motion (resonance)
State the constitutive relation.
D(ω) = ε_0 E(ω) + P(ω)
free space response
material response
Describe the situation in the Drude-Sommerfeld model.
damped oscillations, free electron gas
What is the aim of the Drude-Sommerfeld and Lorentz models?
Obtain an expression for the relative permittivity of the electron gas for a given frequency.
Describe the situation in the Lorentz oscillator model.
Forced, damped oscillations, bound electrons
In what situations are the Lorentz and Drude models accurate.
Lorentz: small wavelengths, high E
Drude: long wavelengths, low E
What kinds of particles are required for surface plasmon resonance?
metal nanoparticles smaller than the wavelengths of incident light
Which model is used to describe surface plasmon resonance?
Drude.
State the condition for surface plasmon resonance.
Re(ε) = -2ε_m -> the polarisability goes to infinity
Describe the scattering effect in surface plasmon resonance.
the scattered field is the same as the field generated by the dipole.
Describe the absorption in surface plasmon resonance.
The metal nanoparticles produce strong absorption at resonance frequency. It is associated with the generation of heat or lower-E photons. Can be used to categorise radius of particles.
Describe the extinction coefficient.
σ_ext = σ_scatt + σ_abs
Describe Plasma Frequency.
natural resonant frequency of the gas when it is displaced from its equilibrium position and the force is removed.
