Optics and Photonics Dr. Kevin Hewitt Office: Dunn 240, Lab: Dunn B31, Friday Sept. 6, 2002

2 Course Information Optics is light at work Textbook: Optics (4 th edition), Eugene Hecht, $ 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

3 Course Information Grading: –Problem sets 20% –Midterm20% –Oral Presentation20% –Final exam40% Problem sets: –1 per week –Hand-out/Hand-in every Wednesday (begin Sept. 11)

4 Class Schedule WeekDatesTopic Key terms 1 Sept. 6 The Nature of light Wave-particle duality 2 Sept Geometrical optics Huygen’s and Fermat’s principles Reflection, refraction, thin lens 3 Sept Matrix methods in paraxial optics System matrix elements, thick lens, cardinal points, Ray transfer matrix 4 Sept Optical instrumentation Optics of the eye Stops, pupils, windows, prisms, cameras, telescopes, Acuity, corrections 5 Sept. 30- Oct. 4 Wave equations and superposition Plane and EM waves, Doppler effect 6 Oct Interference of light Young’s double slit, Dielectric films, Newton’s rings 7 Oct Optical Interferometry Michelson, Fabry-Perot, Resolving power, Free spectral range.

5 Class Schedule Wee k DatesTopic Key terms 8 Oct Fraunhofer diffraction Single slits, multiple slits, rectangular and circular apertures 9 Oct. 28- Nov.1 Gratings Grating equation, Free Spectral Range, Dispersion, Resolution 10 Nov Polarization of light Fresnel equations, Jones vector, birefringence, optical activity, production 11 Nov Laser basics and applications Einstein’s theory, Laser Tweasers 12 Nov Fiber optics & Fourier optics Bandwidth, attenuation, distortion, optical data imaging and processing 13 Nov Holography Class Presentations 14 Dec. 2 Classes end 15 Dec Exam period 3 hour exam

6 Key Dates DateItem 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 Oral Presentations December 2 Classes end December 4-14 Exam period

7 Nature of Light (Hecht 3.6) Optics

8 Nature of Light Particle –Isaac Newton ( ) –Optics Wave –Huygens ( ) –Treatise on Light (1678) Wave-Particle Duality –De Broglie (1924)

9 Young, Fraunhofer and Fresnel (1800s) Light as waves! Interference –Thomas Young’s ( ) double slit experiment –see Diffraction –Fraunhofer (far-field diffraction) –Augustin Fresnel ( ) (near-field diffraction & polarization) Electromagnetic waves –Maxwell ( )

10 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

11 M =  T Cosmic black body background radiation, T = 3K. Rayleigh-Jeans law

12 Planck’s hypothesis (1900) To explain this spectra, Planck assumed light emitted/absorbed in discrete units of energy (quanta), E = n hf E = n hf Thus the light emitted by the blackbody is,

13 Photoelectric Effect (1905) Light as particles Einstein’s ( ) explanation –light as particles = photons Kinetic energy = hƒ - Ф Electrons Light of frequency ƒ Material with work function Ф

14 Luis de Broglie’s hypothesis (1924) Wave and particle picture Postulated that all particles have associated with them a wavelength, For any particle with rest mass m o, treated relativistically,

15 Photons and de Broglie For photons m o = 0 E = pc Since also E = hf But the relation c = ƒ is just what we expect for a harmonic wave

16 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

17 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

18 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

19 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

20 Huygens’ wave front construction Given wave-front at t Allow wavelets to evolve for time Δt r = c Δt ≈ λ New wavefront What about –r direction? See Bruno Rossi Optics. Reading, Mass: Addison-Wesley Publishing Company, 1957, Ch. 1,2 for mathematical explanation Construct the wave front tangent to the wavelets

21 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