Transcript Optics and Photonics

Optics and Photonics
Dr. Kevin Hewitt
Office: Dunn 240, 494-2315
Lab: Dunn B31, 494-2679
[email protected]
Friday Sept. 6, 2002
Course Information
Optics is light at work
Textbook: Optics (4th edition), Eugene Hecht, $152.39
Reference: Introduction to Optics, F. & L. Pedrotti,
Description: Two areas will be covered:
– Geometrical optics:  < dimension of aperture/object
– Wave (i.e. physical) optics:  > dimension of aperture/object
Selected topics:
– What are your areas of interest?
– Lasers, holography, fiber optic communication, functions of the
eye…
Pre-requisites: PHYC 2010/2510 and MATH 2002
2
Course Information
Grading:
– Problem sets
– Midterm
– Oral Presentation
– Final exam
20%
20%
20%
40%
Problem sets:
– 1 per week
– Hand-out/Hand-in every Wednesday (begin
Sept. 11)
3
Class Schedule
Week
Dates
Topic
Key terms
1
Sept. 6
The Nature of light
Wave-particle duality
2
Sept. 9-14
Geometrical optics
Huygen’s and Fermat’s principles
Reflection, refraction, thin lens
3
Sept. 16-21
Matrix methods in paraxial
optics
System matrix elements, thick
lens, cardinal points, Ray transfer
matrix
4
Sept. 23-28
Optical instrumentation
Optics of the eye
Stops, pupils, windows, prisms,
cameras, telescopes,
Acuity, corrections
5
Sept. 30Oct. 4
Wave equations and
superposition
Plane and EM waves, Doppler
effect
6
Oct. 7-12
Interference of light
Young’s double slit, Dielectric films,
Newton’s rings
7
Oct. 14-19
Optical Interferometry
Michelson, Fabry-Perot, Resolving
power, Free spectral range.
4
Class Schedule
Wee
k
Dates
Topic
Key terms
8
Oct. 21 -26
Fraunhofer diffraction
Single slits, multiple slits, rectangular
and circular apertures
9
Oct. 28Nov.1
Gratings
Grating equation, Free Spectral
Range, Dispersion, Resolution
10
Nov. 4 - 9
Polarization of light
Fresnel equations, Jones vector,
birefringence, optical activity,
production
11
Nov. 11 - 16
Laser basics and
applications
Einstein’s theory, Laser Tweasers
12
Nov. 18 - 23
Fiber optics & Fourier optics
Bandwidth, attenuation, distortion,
optical data imaging and processing
13
Nov. 25 -30
Holography
Class Presentations
14
Dec. 2
Classes end
15
Dec. 4 - 14
Exam period
3 hour exam
5
Key Dates
Date
Item
September 20
Last Day to Register
October 7
Last Day to Drop without a “w”
October 14
Thanksgiving Day
October 12
Midterm exam
November 11
Remembrance day
November 4
Last Day to drop with a “W”
Nov. 25-30
Oral Presentations
December 2
Classes end
December 4-14
Exam period
6
Nature of Light (Hecht 3.6)
Optics
7
Nature of Light
Particle
– Isaac Newton (1642-1727)
– Optics
Wave
– Huygens (1629-1695)
– Treatise on Light (1678)
Wave-Particle Duality
– De Broglie (1924)
8
Young, Fraunhofer and Fresnel
(1800s)
Light as waves!
Interference
– Thomas Young’s (1773-1829) double slit experiment
– see http://members.tripod.com/~vsg/interf.htm
Diffraction
– Fraunhofer (far-field diffraction)
– Augustin Fresnel (1788-1827) (near-field diffraction &
polarization)
Electromagnetic waves
– Maxwell (1831-1879)
9
Max Planck’s Blackbody Radiation
(1900)
Light as particles
Blackbody – absorbs all wavelengths and
conversely emits all wavelengths
The observed spectral distribution of
radiation from a perfect blackbody did not
fit classical theory (Rayleigh-Jeans law) 
ultraviolet catastrophe
10
1x10
8
M = T
Spectral Radiance Exitance
2
(W/m - mm)
T = 6000 K
8x10
7
6x10
7
4x10
7
2x10
7
Rayleigh-Jeans law
T = 5000 K
Cosmic black body background
radiation, T = 3K.
T = 3000 K
0
0
2
Wavelength (mm)
11
Planck’s hypothesis (1900)
To explain this spectra, Planck assumed
light emitted/absorbed in discrete units of
energy (quanta),
E = n hf
Thus the light emitted by the blackbody is,

2hc 
1

M ( ) 
hc
5

  e kT  1 
2
12
Photoelectric Effect (1905)
Light as particles
Einstein’s (1879-1955) explanation
– light as particles = photons
Light of frequency ƒ
Kinetic energy = hƒ - Ф
Electrons
Material with work function Ф
13
Luis de Broglie’s hypothesis (1924)
Wave and particle picture
Postulated that all particles have associated
with them a wavelength,
h

p
For any particle with rest mass mo, treated
relativistically,
E  p c  mo c
2
2 2
2 4
14
Photons and de Broglie
For photons mo = 0
E = pc
Since also E = hf
h
h
h
c
 


hf
p E
f
c
c
But the relation c = ƒ is just what we expect for
a harmonic wave
15
Wave-particle duality
All phenomena can be explained using
either the wave or particle picture
Usually, one or the other is most
convenient
In OPTICS we will use the wave picture
predominantly
16
Propagation of light: Huygens’
Principle (Hecht 4.4.2)
E.g. a point source (stone dropped in
water)
Light is emitted in all directions – series of
crests and troughs
Rays – lines
perpendicular to
wave fronts

Wave front - Surface of
constant phase
17
Terminology
Spherical waves – wave fronts are
spherical
Plane waves – wave fronts are planes
Rays – lines perpendicular to wave fronts
in the direction of propagation
x
Planes parallel to y-z plane
18
Huygen’s principle
Every point on a wave front is a source of
secondary wavelets.
i.e. particles in a medium excited by
electric field (E) re-radiate in all directions
i.e. in vacuum, E, B fields associated with
wave act as sources of additional fields
19
Huygens’ wave front construction
New wavefront
Construct the
wave front tangent
to the wavelets
r = c Δt ≈ λ
Given wave-front at t
Allow wavelets to evolve
for time Δt
What about –r direction?
See Bruno Rossi Optics. Reading, Mass:
Addison-Wesley Publishing Company, 1957, Ch. 1,2
for mathematical explanation
20
Plane wave propagation
New wave front is still
a plane as long as
dimensions of wave
front are >> λ
If not, edge effects
become important
Note: no such thing
as a perfect plane
wave, or collimated
beam
21