1. Trivia Question Which famous New Jersey based scientist is credited with invention of the laser? (a) Albert Einstein (b) Niels Bohr (c) Charles Townes (d) Arthur Schawlow (e) Aleksandr Prokhorov (f) Nikolay Basov (g) Sheldon Cooper

2. Trivia Question Which famous New Jersey based scientist is credited with invention of the laser? (a) Albert Einstein – THEORETICAL foundations of lasers 1917 in Germany. (b) Niels Bohr – Argued that lasers would NOT work since they ‘violate’ Heisenberg uncertainty principle. (c) Charles Townes – Developed MASER (1953 Columbia University) and INFRARED laser (1957 – Bell labs in NJ). Nobel Prize 1964. (d) Arthur Schawlow (1957 – Bell labs in NJ) (e) Aleksandr Prokhorov (1964 Nobel Prize in physics for maser-laser principles) - USSR (f) Nikolay Basov (1964 Nobel Prize in physics for maser-laser principles) - USSR (g) Sheldon Cooper – He is a legend in his own mind. (h) Gordon Gould – graduate student at Columbia, coined the term LASER and successfully sued against US Patent Office for inventions related to the laser. Previous slide has copy of Gould’s notebook with first mention of word “LASER” Historians still argue about who invented the laser….

3. Week 6 – Interference Interference of two Point Sources - Movie Animation following crests of wave (constant phase) http://physics-animations.com/Physics/English/1wa_tmp.htm Point Source Notice location of nodes and anti-nodes Animations below illustrate effect of changing PHASE of two sources. Note that the interference pattern is STEERED. Interference Pattern at a fixed distance away (MATHCAD FILE)MATHCAD FILE

4. Use aperture and extended light source to make spatially coherent light https://www.youtube.com/watch?v=XH--q2_m1vM Using apertures to ‘make’ two sources of light is example of ‘Wavefront Splitting’ interferometers. Waves are SPATIALLY coherent since they are ‘cut’ from the same point source. Waves are TEMPORALLY coherent since they are ‘cut’ from the same (or nearly the same) wavefront.

5. Wavefront Splitting Interferometers Fresnel Biprism Link below similar to Lloyd’s mirror https://www.youtube.com/watch?v =CEVuo9QN52M&feature=youtu.b e

6. Reflection from a Boundary Phase of reflection from a boundary depends on mediums on both sides of the interface Reflection animation To be shown later in course: Wave passing from LOWER n to HIGHER n has a 180 degree phase change http://phet.colorado.edu/sims/wave-on-a- string/wave-on-a-string_en.html

7. Interference in Thin Film

10. Reflection from a Boundary Phase of reflection from a boundary depends on mediums on both sides of the interface Reflection animation To be shown later in course: Wave passing from LOWER n to HIGHER n has a 180 degree phase change http://phet.colorado.edu/sims/wave-on-a- string/wave-on-a-string_en.html

11. Soap film interference – Different colors correspond to different thicknesses. Reflectivity (%) Film Thickness (nm)

12. Michelson Interferometer Equivalent linear arrangement.

13. Examples of Interferometers Mach-Zehnder Twyman-Green Rotating Sagnac Sample

14. Multiple Beam Interference

15. Fabry-Perot Inteferometer