Nanooptics

Nanooptics is a field of optics that focuses on the interaction of light with particles or structural features of a material that are smaller than the optical wavelength. The term typically refers to phenomena of visible and near IR light, with a wavelength of approximately 400 nm to 1.2 micrometres.

The interaction of light with these nanoscale features leads to confinement of the electromagnetic field to the surface or tip of the nanostructure resulting in a region referred to as the optical near field. This effect is to some extent analogous to a lightning rod, where the field concentrates at the tip. In this region, the field may need to adjust to the topography of the nanostructure (see boundary conditions of Maxwell's equations). This means that the electromagnetic field will be dependent on the size and shape of the nanostructure that the light is interacting with.

This optical near field can also be described as a surface bound optical oscillation which can vary on length scale of 10's or 100's of nanometers - a length scale smaller than the wavelength of the incoming light. This can provide higher spatial resolution beyond the limitations imposed by the law of diffraction in conventional far-field microscopy. The technique derived from this effect is known as near-field microscopy, and opens up many new possibilities for imaging and spectroscopy on the nanoscale.

Novel optical properties of materials can result from their extremely small size. A typical example of this type of effect is the color change associated with colloidal gold. In contrast to bulk gold, known for its yellow color, gold particles of 10 to 100 nm in size exhibit a rich red color. The critical size where these and related effects take place are correlated with the mean free path of the conduction electrons of the metal.

In addition to these extrinsic size effects that determine a material's optical response to incoming light, the intrinsic properties of the material can change. These size effects occur as particles become even smaller. At this stage some of the intrinsic electronic properties of the medium itself change. One example of this phenomenon is in semiconductor nanostructures where the extremely small particle size confines the quantum mechanical wavefunction, leading to discrete optical transitions, e.g., fluorescence colors that depend on the size of the particle. The changing bandgap of the semiconductor is the reason for this color change. This effect, however, since not directly correlated with optical wavelength, is not unanimously included when referring to nanooptics.

Nanooptics is a field of optics that focuses on the interaction of light with particles or structural features of a material that are smaller than the optical wavelength. The term typically refers to phenomena of visible and near IR light, with a wavelength of approximately 400 nm to 1.2 micrometres.

The interaction of light with these nanoscale features leads to confinement of the electromagnetic field to the surface or tip of the nanostructure resulting in a region referred to as the optical near field. This effect is to some extent analogous to a lightning rod, where the field concentrates at the tip. In this region, the field may need to adjust to the topography of the nanostructure (see boundary conditions of Maxwell's equations). This means that the electromagnetic field will be dependent on the size and shape of the nanostructure that the light is interacting with.

This optical near field can also be described as a surface bound optical oscillation which can vary on length scale of 10's or 100's of nanometers - a length scale smaller than the wavelength of the incoming light. This can provide higher spatial resolution beyond the limitations imposed by the law of diffraction in conventional far-field microscopy. The technique derived from this effect is known as near-field microscopy, and opens up many new possibilities for imaging and spectroscopy on the nanoscale.

Novel optical properties of materials can result from their extremely small size. A typical example of this type of effect is the color change associated with colloidal gold. In contrast to bulk gold, known for its yellow color, gold particles of 10 to 100 nm in size exhibit a rich red color. The critical size where these and related effects take place are correlated with the mean free path of the conduction electrons of the metal.

In addition to these extrinsic size effects that determine a material's optical response to incoming light, the intrinsic properties of the material can change. These size effects occur as particles become even smaller. At this stage some of the intrinsic electronic properties of the medium itself change. One example of this phenomenon is in semiconductor nanostructures where the extremely small particle size confines the quantum mechanical wavefunction, leading to discrete optical transitions, e.g., fluorescence colors that depend on the size of the particle. The changing bandgap of the semiconductor is the reason for this color change. This effect, however, since not directly correlated with optical wavelength, is not unanimously included when referring to nanooptics.