1. Announcements 4/6/12 Prayer Exam 3 ends tomorrow I’ll be on the radio 5 pm tomorrow with the Utah Baroque Ensemble: 89.1 FM or Sirius XM 143 (BYU radio). An hour of classical- style choral music, pieces dating from ~1600 to ~2000. Close to Home

2. Reading Quiz Who developed the “A and B” coefficients? a. a.Avogadro and Boltzmann b. b.Bohr c. c.Einstein d. d.Fermi e. e.Plank

3. Reading Quiz Which of these processes is not one considered in Einstein’s A & B coefficient analysis? a. a.spontaneous absorption b. b.stimulated absorption c. c.spontaneous emission d. d.stimulated emission

4. Two Level System: Three Processes Energy (light, electrical, etc.) AbsorptionEmission light Stimulated Emission Energy (light) light: incident + more

5. A & B for a Two Level System and application to lasers

6. Lasers Principal components: 1. Gain medium 2. Laser pumping energy 3. High reflector 4. Output coupler 5. Laser beam Image & list from Wikipedia

7. From Saleh & Teich, Fundamentals of Photonics (2007)

8. From Wikipedia Lasers!!

9. From Saleh & Teich, Fundamentals of Photonics (2007) Semiconductor Alloys

10. From http://www.tf.uni-kiel.de/matwis/amat/semi_en/kap_5/backbone/r5_1_4.htmlhttp://www.tf.uni-kiel.de/matwis/amat/semi_en/kap_5/backbone/r5_1_4.html Bandgap Engineering Quotes from web page author