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Gaussian Beams and Laser Stability Quiz Reminder

Reminder for HW#23 due Saturday & potential schedule change poll. Review exam problems on Monday. Submit solutions in PDF by 1:45pm. Reading quiz on Gaussian beams topics.

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Gaussian Beams and Laser Stability Quiz Reminder

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  1. Announcements 3/30/12 • Prayer • HW 23 is due Saturday night. • Poll: should we have it due Monday and start exam on Tuesday? (Exam would still end Friday night) • Exam review problems on Monday. • Get your solutions to me in pdf form before 1:45 pm. • Approx. 5.5 mins/group Speed Bump

  2. Reading Quiz • The “Diffraction of a Gaussian field profile” section involves diffraction through: • a circular aperture • a square aperture • no aperture

  3. Reading Quiz • The smallest radius of a laser beam is known as the beam _______: • ankle • knee • neck • pinky • waist

  4. Reading Quiz • The distance over which the beam radius near a focus stays about constant is the _______ range. • Fresnel • Gaussian • Home_on_the • Plank • Rayleigh

  5. Gaussian field profile • E0 = Gaussian shape • Fresnel approximation • Diffracting through infinitely large aperture

  6. Gaussian beams: result (r = cylindrical r) Rayleigh Range beam width relates to curvature: plane wave to spherical wave transition

  7. A few different z values

  8. Some plots Original Gaussian profile: width = 1 height = 1 At z = ½ z0 width = 1.12 height = 0.8 At z = z0 width = 1.41 height = 0.5 At z = 2 z0 width = 2.24 height = 0.2 At z = 4 z0 width = 4.12 height = 0.059

  9. Beam width vs. distance This is width vs. z, for a beam with a larger Rayleigh range—stays near the waist for longer. But doesn’t get as narrow!

  10. What happens at large z

  11. Beam width vs. distance Figures from P&W

  12. Unspoken assumption about wavefronts at z=0

  13. Gaussian Wavefronts Plane Spherical (Figures from Saleh and Teich, Photonics, 2nd edition, pg 82) Gaussian

  14. The three phase factors (r = cylindrical r) Rayleigh Range relates to curvature: plane wave to spherical wave transition

  15. More complicated modes

  16. Gaussian beams & laser stability

  17. Reading Quiz • The ABCD law for Gaussian beams is used for: • finding the ABCD matrices for a Gaussian laser beam • finding the diffraction pattern in the near-field • finding the Gaussian beam parameters after an optical element

  18. ABCD Law for Gaussian beams

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