Limits and Interfaces in Sciences / Kumboldt-Kolleg São Paulo-SP, 28 th - 30 th October 2009

1.Introduction 2.Scanning near-field optical microscope (SNOM) probe for controlling Raman microlaser action 3.SNOM probe as a tool for controlling the interaction of a nanoscopic light emitter with confined electromagnetic field Motivation  Using scanning probe tech- niques (SNOM) for controlling and manipulating confined light in microresonators, as well as to control the interaction of single nanoparticles with it.

St. Paul´s cathedral, London Lord Rayleigh, m 15 µm  Easily produced by melting an optical fiber with a CO 2 laser.  Diameters from 20  m to 200  m.  Q factors up to  May store photons for some  s.  Comparison: tuning fork 550 Hz, same Q: oscillates for 4 days!!!  Modal volume V~300  3  Evanescent field allows the external coupling. Braginsky et al., Phys. Lett. A 137, 393 (1989); L. Collot et al., Eur. Phys. Lett. 23, 327 (1993).  Light is trapped in a whispering gallery mode by successive total internal reflections, travel- ling in a great circle along the cavity's perimeter. Microspheres as optical cavities 100  m Represent optical resonators with ultra-high Q-factors and small mode volumes. ~33 m

Spectroscopy of the microspheres´ eigenmodes Typical spectrum measured by absorption and scattering

 Constant distance (~10 nm) between the microsphere sur- face and the SNOM tip via a shear force control loop.  Tip-limited (~50 nm) optical resolution.  Allows getting a topogra- phical image. Scanning Near-field Optical Microscopy 20mm

For Q = 10 9, P threshold = 4.3  W  world record!  =70  m Q=3  10 8 =795nm 4 mm

Pump mode 795 nm) Laser mode 814 nm) Tip reduces the Q-factor of the WGM  laser threshold increases A. Mazzei et al., Appl. Phys. Lett. 89, (2006).

Fluorescence microscope images of a single 200 nm dye-doped bead attached to a SNOM tip Without notch filter With notch filter

200 nm 200 nm in diameter dye-doped bead S. Götzinger et al., Nano Lett. 6, 1151 (2006).

via  scope via prism S. Götzinger et al., J. Opt. B: Quantum Semiclass. Opt. 6, 154 (2004). Coupling of single semiconductor quantum dots:

Multimode fiber connected to PMT PrismCollimating lens Monomode fiber socket Rotation stage Monomode fiber with collimating and focus- sing lenses Goniometer Confocal microscope obejctive Temperature stabilized Cu block Stabilized 3D piezo stack Cu tube with microsphere

Cavity-mediated photon transfer Intensity (arb. units) Wavelength (nm) Intensity (arb. units) Wavelength (nm) S. Götzinger et al., Nano Lett. 6, 1151 (2006).  Our calculations show that the transfer efficiency is 10 6 times larger that in free space! exc =532nm  =35  m

By using our setup, we have obtained cavity-mediated enhanced pho- ton transfer between two single nanoparticles. We have used silica microspheres to observe an ultralow threshold Raman microlaser action and used a SNOM probe to control it. We have shown how to fabricate microresonators presenting resonan- ces with ultrahigh quality factors, i.e., ultralong photon storage times. Thank you for your attention!!! And pretty close to our labs... Baía dos Porcos, Fernando de Noronha-PE A single nanoparticle was attached to the end of a near-field probe. The coupling to a high-Q WGM was obtained in a very controlled way.