Welcome to the Home Page for

Quantum Electronics


Spring Term '98

Professor George W. Pratt

MIT Room 13-3057

Telephone: 617/253-4636

Fax: 617/258-6640

Quantum Electronics 6.751 Spring Term '98

Tuesday & Thursday 2:30 - 4:00 Room 36-153


The basic text is Loudon's"Quantum Theory of Light" Second Edition Oxford Univ Press. A second very useful text is "Laser Electronics" 2nd Edition by J.T.Verdeyen. This emphasizes the applied aspects and is the source of lots of good problems of a practical nature. The overall objective is to develop a deep understanding of optical phenomena with particular emphasis on the workings of the laser. The course starts with the Einstein model of optical transitions which was set forth 20 years before the advent of the Schrodinger equation. Einstein's brilliant leap of imagination was made at a time when even the existence of atoms was controversial; so much so that Boltzmann committed suicide over the issue. Following the implications of the Einstein model we move to a quantum mechanical description of an optical transition between two electronic states keeping a classical description of the electromagnetic field. Next we read a classic paper by Lamb which is an elegant treatment of the laser but not the tour de force that Loudon presents later in his book. After Lamb's paper it is back to Loudon for a description of the classical electromagnetic field and the statistical properties of photons. This is followed by an explanation of first and second order coherence. Very surprising things emerge. A light beam impinging on two slits in a screen produce a diffraction pattern of a viewing screen. This even happens if only one photon at a time strikes the two slit screen. How can this be? Must not a single photon go through one or the other slit? If this is true how do we get interference fringes? Very strange but all will be explained. The next topic is the quantization of the electromagnetic field. This allows us to prove the assumptions made by Einstein that stimulated emission is a process in which photons produce exact copies ie. clones of themselves. We will see that electronic states are in fact mixtures of electronic and photon states; the so-called dressed states. Its time to take a break and have some fun so we read a great little book by Feynman called QED The Strange Theory of Light and Matter. Here the issue of whether a photon is a particle or a wave or both is settled. The answer may surprise you. Next we come to the coherent state of the quantized radiation field and its properties. Now Loudon has prepared the way for a truly sophisticated treatment of the laser . Below threshold the light is incoherent but above threshold it becomes coherent. We learned about threshold from Lamb's paper. These changes on going through threshold interestingly resemble the superconductor normal transition. Finally we finish with a treatment of non-linear optics. Throughout the course xeroxed material adds to your reading burden. These additions are mostly tutorial papers on a variety of topic such as squeezed light, frustrated spontaneous emission, laser linewidth, etc. The Table of Contents from Loudon follows. There is no final exam and the course grade is based primarily, sometimes exclusively, on the weekly homework assignments.

Chapter 1

Plank's Radiation Law and the Einstein Coefficients

Chapter 2

Quantum Mechanics of the Atom-Radiation Interaction

Chapter 3

Fluctuation Properties of Chaotic Light

Coherence, Double Slit Diffraction, Hanbury Brown and Twiss Experiment

Chapter 4

The Quantized Radiation Field

The quantum mechanical harmonic oscillator, vacuum fluctuations, coherent state

Chapter 5

Interaction of Quantized Field with Atoms

Electric dipole approx. , photoelectric effect, dressed states, time dep. perturbations

Chapter 6

Photon Optics

Quantum theory of diffraction, squeezed states, photon counting

Chapter 7

Generation and Amplification of Light

This is the Loudon's tour de force, the quantum theory of the laser, magnifique!

Chapter 8

Resonance Fluorescence and Light Scattering

Resonance flourescence, Raman and Rayleigh scattering, two photon processes

Chapter 9

Non Linear Optics

Prof G. W. Pratt 13-3057 Tel 253-4636 gwpratt@mit.edu