бредовые доклады
Sep. 7th, 2010 05:05 pm![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
zorgeoПоручили мне вести часть модуля Topics in Physics. Идея не такая уж дурная, как кажется на первый взгляд. Каждый лектор рассказывает детишкам веселые фенечки с переднего края своей науки, а студенты потом читают, ищут литературу и делают доклад в рамках этой области по выбранной темы. моя облясть - явления ближнего поля в оптике. всякое нано-, мета- и т.д. я набросал несколько тем на выбор. это все очень сырое. буду признателен за любые отзывы. и не бить за мой английский, я надеюсь, коллеги потом это слегка причешут.
Topics for Talks
1. Near-field optical microscopy using optical fibres.
Describe the near-field optical probe – a tapered optical
fibre with a subwavelength aperture at the end. Discuss the characteristics of
the optical field near the aperture: its spatial extension, intensity
throughput, polarization. Cover various applications of SNOM, including
different modes of operation: transmission, fluorescence, magneto-optical SNOM,
etc. Mention the topographic control of the near-field probes.
2. Apertureless near-field optical microscopy.
Scanning near-field optical microscopy with a scattering
light source is described. Various source materials are compared. Enhancement
of the near-field is explained, and quantitative examples given. Applications
of scattering-type SNOM are discussed, with main emphasis on multiphoton
effects such as Raman scattering.
3. Light scattering by nanoparticles.
Polarization of metallic and dielectric particles in an
applied electric field is described. Rayleigh theory of scattering is derived and
illustrated by practical examples. Applications of scattering nanoparticles
from the ancient times to the modern technologies are described.
4. Rainbows.
Describe the geometrical optics model of light in a
raindrop. Discuss 1st and 2nd order rainbows. Introduce
the notion of a caustic. Explain the dispersion of water in the visible optical
range. Describe the colour of the sky outside the rainbow. You may talk about
interference effects in a rain drop. Picturesque photos either borrowed from
literature or shot by students are welcome.
5. Historical proofs of wave nature of light.
Describe the first experiments proving the wave character of
light. Newton’s rings and Poisson’s spot are good examples. Describe the
controversy between the wave and particle theory of light and tell how modern
quantum physics deals with it. It would be good if students could run a little
demonstration of wave nature of light during the presentation.
6. Near-field-coupled resonators.
This is mainly a theoretical talk about dipolar sources of
light that have Lorentzian resonance lineshape. Describe the interaction
between the dipoles in the near-field zone. Derive the normal modes of two
weakly coupled identical oscillators, discuss the eigenfrequency splitting and
quality factors of the modes depending on coupling strength. Distinguish
between “dark” and “bright” modes of a dimer in relation with its orientation
and the polarization of incident light. Show the illustrative “spring” model.
Give a practical example for gold or silver nanoparticles.
7. Fano resonance.
This is mainly a theoretical talk describing the scattering
of nanoparticles in the presence of the excitation field “leaking” into the
detection system. Using pseudo-classical Lorentz lineshape, derive the Fano
resonance characteristics. Introduce the complex plane diagram to illustrate
the Fano resonance geometrically. Give practical examples.
8. Colours of stains and pollutants.
Describe the reflection of light from dielectric and
metallic surfaces. Describe the spectrum of reflected light, when a dielectric
is covered by a thin layer of another one. Discuss the antireflection coatings.
Explain the rainbow colour of oil drops on water, of dry ink on glass, etc.
Tell about practical applications of this effect (ellipsometry, interferometry).
The presentation should be accompanied by real demonstrations and samples.
9. Near-, medium- and far-field dipolar radiation.
This is a theoretical talk describing the electromagnetic
radiation of a harmonically oscillating electric dipole. Give the full
expression of the field, tell about the applicability of the electrostatic
approximation. Discuss the distance dependency of the radiation in the far
field, draw a conclusion based on the energy conservation principle. Describe
the angular distribution of the field in the near- and far-field zones. You may
extend this talk by introducing higher-order multipoles or by considering
practical applications such as antennae design.
10. Structured illumination microscopy.
Describe the alternative approach to achieving subwavelength
optical resolution without a near-field probe. Introduce the concept of spatial
frequency mixing and moiré patterns. Give a simple theory of image
reconstruction for 1-dimensional structured illumination. Speak about practical
schemes to produce structured illumination, tell about their limitations and
prospects.
11. Optical metamaterials.
Describe the refractive index of dielectrics at optical
frequencies as a function of electric permittivity and magnetic permeability.
Explain why natural materials are non-magnetic at optical frequencies. Tell how
to make optical building blocks – metamolecules – that have magnetic
properties. Describe various production techniques and various applications:
Harry Potter’s invisibility cloak, anti-radar systems, etc.
12. Ultraslow and ultrafast light.
Introduce the concept of light dispersion. Explain the
dispersion relation of common optical materials, such as glass and metals. Tell
about phase and group velocity. Describe the stopped light in a photonic
crystal. Describe the seemingly superluminal motion of light in an optically
active medium (laser resonator). Give other examples of superluminal motion.
Describe the paradoxes associated with superluminal motion and the fundamental
character of speed of light.
13. Surface plasmon-polaritons.
Describe the collective excitations of electrons that exist
on a metal-dielectric interface. Derive the expression of the SPP wavevector
(plasmon dispersion) and the decay length parameters of the evanescent wave in
the dielectric and metal. Discuss the possibility of coupling between SPP and
propagating plane waves in a dielectric. Describe the Kretschmann and Otto
configurations for excitation of SPP. Illustrate the talk with the reflectance
angular dependency with SPP resonant peak. You may describe SPP applications in
biosensing.
14. Whispering gallery modes.
Give a historic overview of whispering gallery modes in
acoustics and optics. Describe the geometrical optics model for light rays
trapped in a spherical resonator by total internal reflection; give the
conditions of total internal reflection. Describe the wave optics model of
WGMs, introduce the phase matching condition for constructive self-interference
of the wave. Estimate the near-field decay length. Explain how WGMs can be used
in biosensing.
15. Left-handed optical media.
Describe the early theoretical work by V. Veselago on
negative refraction index. Describe the material properties that are required
for negative refraction index and why they were not observed in 1960-s. Show
how these complications were overcame in 2000-s (J. Pendry). List possible
consequences of negative refraction: perfect lens, invisibility cloak, inverse
Doppler effect, negative radiation pressure. Describe the practical
realizations of left-handed metamaterials in radio frequencies and in the
optical range.
16. Polarization of light upon reflection and refraction.
Introduce the boundary conditions of Maxwell equations. Tell
how these conditions define the angles of reflection and refraction (Snell’s
law). Describe the Fresnel equations for refraction and reflection. Tell about
linear dichroism of reflection. Explain what a Brewster’s angle is, and why it
is only observed for p-polarization. Give a simple geometrical interpretation
within the dipolar model of a dielectric. Derive the complex character of
Fresnel coefficient for total internal reflection and for reflection from
metals. Explain why an arbitrarily linearly polarised light becomes
elliptically polarised upon the total internal reflection. Describe the
practical applications of polarization changes upon reflection and refraction
(i.e., Glan–Thompson prism).
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no subject
Date: 2010-09-07 07:59 pm (UTC)no subject
Date: 2010-09-07 08:40 pm (UTC)кстати, от тебя я также узнал, что такое www. давно было.
no subject
Date: 2010-09-07 09:21 pm (UTC)ya tebe i ne takoe rasskazhu. u nas est' takie shtuki - tipa telefona, no bez provoda. mozhno v karmane s soboj nosit'. na nekotoryh iz nih dazhe mozhno www delat'.
a super-prodvinutymi mozno i nsom delat' :-)
no subject
Date: 2010-09-08 12:59 pm (UTC)