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

Trivia QuestionWhich 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….

Interference of Two Waves

Let’s consider interference of (a) co-linear waves and (b) waves overlapping obliquely (at some angle).

2 1

Wavefront Splitting Interferometers

Fresnel Biprism

Third animation from link below similar to Lloyd’s mirror

http://physics-animations.com/Physics/English/1wa_tmp.htm

Examples of co-linear interference (Interferometers)

Examples of Interferometers

Mach-ZehnderTwyman-Green

Rotating Sagnac

Sample

Conservation of Energy in Interferometers

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:

1 2

1 2

n nrn n

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

Conservation of Energy in Interferometers

Interference of two waves at an angle theta

Sample Problem EX 2.5-2

Interference of two Point Sources - Movie

Animation following crests of wave (constant phase)Point Source

Notice location of nodes and anti-nodes

Multiple Slit Interference

Sum of waves LARGEST when where n is an integer.

Where does power come from to give LARGE power in the peaks?

2 n

Fabry-Perot filter

Fourier TIME transforms of Wave FunctionReal function u(r,t) has symmetric peaks for positive and negative frequencies

Fourier Transform of Pulses