Beads help map the optical near-field

A team of researchers from INAC, LTM, and Institut de Bourgogne showed that it is possible to map optical near-fi eld phenomena in silicon nanocavities without using combined optical-AFM techniques like near-fi eld scanning optical microscopy (SNOM). They did it using a camera, a regular microscope and 0.5 micron fl uorescent beads, achieving resolutions comparable to SNOM, a tenth of the cavity wavelength.

Here’s how it works: the nanocavity is placed in a fl uid cell measuring 1 sq. cm in area and 20 microns high, forming a “pool.” The microbeads immersed in the pool move along trajectories determined by the optical forces that the cavity generates. Therefore, the beads’ trajectories reveal the nanopatterns of the cavity’s resonant modes. A patent application has been fi led.

Publication: Optofl uidic Near-Field Optical Microscopy: Near-Field Mapping of a Silicon Nanocavity Using Trapped Microbeads. ACS Photonics, 2015, 2 (10), pp 1410–1415

Contact: joseluis.gonzalezjimenez@cea.fr

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