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Lecture 23 Laser cooling; cold atoms & ions

Lecture 23 Laser cooling; cold atoms & ions. Reminder: Lecture notes taker: none(?) HWK 5 problem 12.3 deleted (assigned before); due date Wed 4/30 class Paper due Wed 4/30 Final exam date: 5/5 Monday evening 7-9pm Room 201 self-made 1 eq. sheet permitted; FQ (all) + FO (1-5)

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Lecture 23 Laser cooling; cold atoms & ions

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  1. Lecture 23Laser cooling; cold atoms & ions Reminder: Lecture notes taker: none(?) HWK 5 problem 12.3 deleted (assigned before); due date Wed 4/30 class Paper due Wed 4/30 Final exam date: 5/5 Monday evening 7-9pm Room 201 self-made 1 eq. sheet permitted; FQ (all) + FO (1-5) Please fill out course evaluation

  2. Bagwell Lecture 2014 New frontiers in Optics and Photonics with Designer Electronic and Optical Materials Federico Capasso, Professor and Research Fellow, Harvard University The control of electrons and photons in artificially structured materials at the nanoscale by quantum and electromagnetic design has opened unique opportunities for major advances in science and technology. I will present a tutorial account of some these developments. From the design of the electronic resonances  and their coupling to light in nanometer thick materials a new class of light sources (quantum cascade lasers) has emerged that now cover almost the entire infrared and far-infrared spectrum, leading to an explosive growth in applications.   By structuring surfaces at the sub-wavelength with nanoscale optical resonators and nanometer thin layers “metasurfaces" have emerged that have led to powerful generalizations of the laws or reflection and refraction, new thin film interferences and new ways to generate light beams and surface optical waves with “arbitrary” wavefronts.  Applications of this new “flat optics” will be presented. Finally, I will show how quantum fluctuations at the nanoscale can be designed to control macroscopic quantum electrodynamical phenomena such as attractive and repulsive Casimir forces and their interaction with micro/nanomechanical structures.   May 14 2 – 3pm burton morgan room 121

  3. Course Outline Part 1: basic review: Optics+Quantum; Part 2: Basic Light-matter interaction; laser; Part 3: Quantum Optics of photons Part 4: More advanced light-matter interaction Part 5: Quantum information/photonics/ applications Subject to change; Check updates on course web/wiki

  4. Plan today (FQ Chap 11) Further studies: Metcalf & van der Straten: laser cooling & trapping Student Presentation: Brian Fields: Introduction to trapped ions and applications in quantum computing

  5. Laser Cooling The most “nobel” idea! 1981 2012 1989 2005 D.J. Wineland, H. Dehmelt:  Bull. Am. Phys. SOC. 20, 637 (1975) Neutral atoms ions Laser cooling/trapping 1997 Atomic BEC 2001

  6. Laser cooling: basic idea • Light force (momentum transfer) • Doppler effect Absorption-emission (even works for solid)

  7. Doppler cooling force (doppler limit)

  8. Optical Molasses (Doppler temperature) (~.1mK)

  9. Actually works better: subdoppler cooling Absorption-emission Recoil limit (~ uK)

  10. Experimental implementation Zeeman slower

  11. Creating BECs @ Purdue (slides by A. Olson) s+ Icurr s- s- s+ s+ Icurr s-

  12. Experimental Setup Credit: Ping Wang design and initial construction Rb87 • 7 lasers • >220 optical components • >45 Electronic devices • Computer control • Vacuum system • Imaging system Elliptical High Pressure MOT 4.5mm Science Chamber MOT 15mm

  13. Absorption Imaging ANDOR iXon EMCCD Lens system: NA is 0.19 and resolution is 2.5 um. Resonant Laser 8x8um pixels. Magnification gives 4.3 um/px 30 mm diameter 80 mm fl Gradium lens 50 mm diameter 150 mm fl Achromatic doublet s+ Icurr s- s- s+ s+ Icurr s-

  14. TOF Absorption Imaging Time of flight imaging 3.4 mm Imaging pulse MOT Lasers / Mag fields t TOF (0 to 20 ms)

  15. Evaporative cooling in optical traps Far off-resonance dipole traps: 30 W of 1550 nm light Waferboard / Flickr

  16. Loading the Dipole Trap 3.4 mm

  17. Cold Atom Collisions Two-body collisions: Thermalization and evaporation Forced evaporation

  18. Lowering final trap depth (15 ms TOF) Theory Results 80 um

  19. Lowering final trap depth (15 ms TOF) Quantum Description With mean field approximation, described by Gross-Pitaevskii equation 80 um Kinetic Potential Contact (Mean field)

  20. Experimental AMO (esp. cold atoms) research --- “seeing” quantum mechanics & dynamics! (“slowed down” and “blown up” so much that you can shoot photos & videos!) Demo with our Bose-Einstein Condensation (BEC) Purdue QMD’s “all-optical” Rb87 BEC apparatus With synthetic gauge fields and spin-orbit coupling “coldest place in Indiana” (<50nK) -- laser cooled & trapped atoms in PHYS G61 RF driven spin Rai oscillation mF=-1 0 +1 Spins (mf ) -1 0 +1 (Stern-Gerlach: separate BECs with different spins) BEC (matter wave) diffraction from laser standing wave (optical grating) coherent oscillation of BEC between 3 spin states B-field gradient

  21. Atom (quantum) Optics & Atom Laser

  22. Signatures of BEC • Bimodal distribution • Anisotropic expansion • Matter interference • superfluidity Cornell/Weiman ketterle

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