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This review session for the Laser Optics course (Phys460) covers the final class topics, including the importance of lasers, population rate equations, and their applications in technology such as telecommunications and holography. We discuss the scattering cross-section area and the intensity of changes in population rates. Attendees will engage with rate equations governing two-level systems and learn about spatial and temporal properties of laser beams. Additional notes include upcoming problem set deadlines and reading assignments to deepen understanding of these critical principles.
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Agenda • Last class review-we built a laser! • Why is it useful? • How does occupation probability evolve? Population rate equations • Changes in population are all fine and good but the important parameter is intensity: • First step: determine scattering cross-section area ASIDE: Problem set #5 due November 24th. Problem set#6 due December 3rd. To be handed out. ASIDE: Reading for next class: M.E. pp 255-258 ASIDE: Review class – December 11th (Saturday) 1:30-2:30 STI 412B If you do not have card access to the building, contact me. “Public” office hour – December 7th 10:30-11:30 STI 412B M.E.: 211-212 M.E.: 214-219 Laser Optics – Phys460
E2 E1 1. Last class review • Included dephasing • If dephasing is much faster than any other process, we are in adiabatically following regime, where: Laser Optics – Phys460
1. Review, cont. • Built a laser! Require N2>N1 IMAG REAL Laser Optics – Phys460
x Wavefronts: z 2. So what? • Why is the laser so important? • Spatial properties: Gaussian beam! • Frequency properties: wavelength determined by quantum system and cavity. • Temporal properties: constant oscillation over time R=.99 Focus tightly Guide over long distances with low loss Spatial coherence (uniform wavefront) • Can be close to monochromatic • Can have broad spectrum Temporal coherence! Laser Optics – Phys460
2. Important?, cont. • Review some of the applications we have considered\. What properties did we assume about our light sources? • C.D. player reader – focus tightly • Holography – plane waves, monochromatic light • Telecommunications • coupling to single mode fiber – focus tightly (steady-state constructive/destructive interference in space!) • short pulses (steady-state constructive/destructive interference in time) • Fourier optics – plane waves, monochromatic beams • Optical tweezers – focus tightly • Laser cooling – control frequency in very precise way Laser Optics – Phys460
3. Population rate equations Laser Optics – Phys460
3. Rate equations, cont. A two-level system starts in the ground state. A resonant optical beam is turned on. What is the subsequent time evolution of the two-level system? For a specific value of and negligible spontaneous emission! 11 22 Laser Optics – Phys460
3. Rate equations, cont. A two-level system starts in the ground state. A resonant optical beam is turned on. What is the subsequent time evolution of the two-level system? For a specific value of and non-negligible spontaneous emission! 11 22 Laser Optics – Phys460
3. Rate equations, cont. If spontaneous emission can be neglected, what is the steady-state occupation probabilities of a two-level system interacting with a NON-resonant optical field? 11 A) 11 =0 and 22 =0 B) 11 =1 and 22 =0 C) 11 =0 and 22 =1 D) 11 =0.5 and 22 =0.5 22 E) None of the above. Laser Optics – Phys460
