Fractal fiber for enhanced throughput SNOM probes

Scanning near-field optical microscopy (SNOM), or NSOM as it otherwise referred to, is the leading instrument used to image optical fields on the nanometric scale. Systems typically employ tapered metal-coated optical fiber probes with a subwavelength aperture at the tip for near-field imaging in various fields spanning nanotechnology and biotechnology. The key limitation with this type of probe is the excessive loss that occurs, which effectively limits the potential applications. Low power throughput means slow scanning speeds and is the major limitation still facing the technology today. The high losses originate from transmission through the subwavelength aperture and transmission through the metal-coated tapered region of the probe. The losses due to the aperture cannot be avoided for apertured probes but the throughput can be improved using a number of techniques. Enhancing the confinement properties of the optical fiber itself using novel structured fiber designs offers a means to reduce the interaction with the metal-coating and the associated losses.