Announcements 11/19/12 Prayer Quick demo: diffraction from a hair Lab 10 due tomorrow Exam 3 starts Monday after break, goes through

Saturday Exam 3 review session: Monday after break, 4:30-6

pm, this room Final exam: in Testing Center, M-Th week of finals

Frank & Ernest

From warmup

Extra time on?a. It would be nice to talk about the last parts

of Chapter 10, it was hard to understand his explanation of the [wave]plates because it was a lot at once.

Other comments?

a. Is there any simple way to describe the quantum mechanics of lasers??? I want to know how they work.

From warmup

Which of the following is NOT true of the 3D “wave vector”?

a. Its magnitude is equal to 2π/λ.b. For every point inside a plane wave,

it points the same direction.c. For every point inside a spherical

wave, it points the same direction.d. It tells us which way the wave is

going.e. In 1D it reduces to the wave number

k.

Waves in 3-dimensions

Plane wavesa. polarization

Wave vectora. direction of wave

Spherical waves

ˆ cos0 x y zE k x k y k z t E pGeneral Form

1ˆ ˆ cos

20E kz t E x + y

Specific Example

Student-designed problem: Transverse Wave

What direction do you want the wave to be traveling in?

What direction do you want the wave to be oscillating in?

What wavelength do you want the wave to have?

What do you want the wave’s amplitude to be?

What frequency (or velocity) do you want the wave to have?

What do you want the overall phase of the wave to be?

Clicker question

How many lasers do you have in your house/apartment?

a. 0b. 1c. 2d. 3e. 4+

From warmup Name one cool thing about lasers that you didn't know prior to this

reading assignment. a. Lasers can help cool down temperatures to less than one

millionth of a degree above absolute zero. (5 students)b. The number which shocked me the most was the specificity of

wavelength – that 99.99999999 percent of all light would be filtered away. (4 students)

c. It works by quantum mechanics. (3 students)d. they can be focused more than regular light which make them

useful for things like surgery or welding (2 students)e. I didn't know that some of the qualities of lasers cannot possibly

be mimicked by conventional light bulbs. -"higher order coherences“ ( 2 students)

f. Lasers are coherent sources of light.g. Laboratory lasers produce light with wavelength variations of

only 10^-6 nmh. They are extremely efficient in regards to energy use.i. they are used to read and write CD'sj. It was really cool learning more how they are made…k. I watched Megamind on Friday, and wondered why Titan's laser

eyes were melting and burnign the city away. Now I know why and he must have had powerful eyes.

Lasers

What makes a laser special?

a. Single wavelengthb. Intensec. Collimatedd. Coherence (spatial,

temporal)

Actual laser spectrum is over 100

narrower than the width of the red line

Blackbody spectrum

Laser spectrum

Lasers

Principal components:1. Gain medium2. Laser pumping energy3. High reflector4. Output coupler5. Laser beam

Energy (light,

electrical, etc.)

AbsorptionEmission

light

Stimulated Emission

Image & list from Wikipedia

Energy (light)

More Wikipedia

Green laser pointer

1. gain medium(Nd:YVO4 crystal)

2. laser pumping energy (808 nm LED beam)

3. high reflector

4. output coupler

5. laser beam

More Wikipedia

Circular Polarization

Pictures from Wikipedia

Remember these pictures?Blue & green both represent electric fields. Ex out of phase with Ey.

Optical Retarders, aka “Wave plates”

Quartz, SiO2: no = 1.544, ne = 1.553

Calcite, CaCO3: no = 1.658, ne = 1.486

Pictures from Wikipedia

Calcite crystal:

Optical Modulators

Electro-optic modulator Acousto-optic modulator

AOM

EOM

www.newport.com wikipedia

Field changes vertical index of

refraction