2010-04-19

Dr. Didier Casse and his team of researchers at the Electronic Materials Research Institute at Northeastern University have recently published Super-Resolution Imaging Using a Three-Dimensional Metamaterials Nanolens, which appeared online in Applied Physics Letters in January, 2010, and went on to become APL's 5th most downloaded paper.

Super-resolution imaging beyond Abbe’s diffraction limit can be achieved by utilizing an optical medium or "metamaterial" that can either amplify or transport the decaying near-field evanescent waves that carry subwavelength features of objects.

This important finding was attained throught the utilization of a Nanonics' Multiview 2000TM System. Says Dr. Casse:

"The Nanonics Multiview 2000TM system has been instrumental for our research breakthroughs in nano-optics at Northeastern University."

A summary of the article follows.

A heterodyne interferometric near-field scanning optical microscope (NSOM) setup has recently been assembled at the Electronic Materials Research Institute (Northeastern University) for advanced optical characterization. The newly-built experimental setup to characterize the PhCs structures is illustrated in Fig.1. A continuous wave (CW) tunable semiconductor IR laser (1510–1580 nm) light is first sent through an optical amplifier to boost the power up to hundreds of mW. The laser beam is then split by a fiber coupler into two branches or arms. The “reference” arm is sent through two acousto-optic modulators (AOMs) that shift the frequency by 60 MHz and then by –60.07 MHz to produce a detuned beam of 70 kHz, which subsequently travels through an optical delay line for amplitude and phase separation purposes (if needed). This method of detuning the beam increases the signal-to-noise ratio and is equivalent to using an optical chopper. Light from the “signal” arm is coupled into the metamaterials structure. The light transmitted through the sample is then picked up by an NSOM probe. Light from both “signal” and “reference” arms are recombined by another fiber coupler and travels to a nitrogen-cooled germanium photodetector. Finally, the signal from the detector is sent to a lock-in amplifier, which is also fed by the difference signal that drives the two AOMs, leading to measurements of intensity (as well as amplitude/phase).

A schematic of the experiment is shown in Fig. 2.