1. Trivia Question Under President Ronald Reagan, what was the nickname of the science initiative to develop, among other things, a laser which could should down a ballistic missile? (a) The Bourne Initiative (b) Avatar Missile System (c) The 2001 Initiative (d) Star Wars Initiative (e) Metal Storm

2. Diffraction: Light does not like to be confined

3. Examples of Diffraction Knife edge Light passing by a sharp edge

4. Examples of Diffraction Waves passing through a small hole http://physics-animations.com/Physics/English/1wd_tmp.htm

5. Examples of Diffraction Focusing light with a lens Geometric Optics – Wavelength small compared to other dimensions. No Diffraction. Light focuses to a point. Wave Optics – Wavelength can be comparable to other dimensions. Diffraction MUST be considered. Light focuses to a minimum spot size. oo

6. Spherical, parabolic, and plane waves

7. Gaussian Beams

8. Intensity dependence

9. Beam Width

10. Gouy Phase Shift The TOTAL change in phase from a COLLIMATED beam at Z=-inifinity to Z=+infinity is π.

11. Gouy Phase Shift Example - THz (C) Measured reflected THz waveform from a typical grape (solid black curve). The dashed black curve corresponds to an added correction for the frequency dependent reflectivity of the berry but no correction to the phase shift. The addition of a −π=2 phase shift (gray curve) accurately reproduces the measured waveform. Federici et. al, Appl. Opt. (7) 48, p1382 (2009)

12. Beam Transmission through Lens

13. Transformation of Beam Parameters by a Lens

14. Minimum spot size of a lens

15. Smallest spot size from Collimated Beam

16. Example 3.2-3

17. MIDTERM DATE Monday march 9 th 1-2:30

18. Sample Problem – Visible Pump/ THz Probe measurement GENERALLY, you typically would like to use GAUSSIAN beams in optics experiments However, Gaussian beams are not the only solution to the wave equation. A more general solution are Hermite-Gaussian Beams: The X and Y functions are Hermite Polynomials.

19. Hermite Polynomials Hermite Polynomials are defined by a recurrence relation

20. Your laser beams may not be Gaussian! ‘Doughnut’ mode is a combination of the (0,1) and (1,0) modes.