Nature Nanophotonics

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Nanophotonics has emerged as a new and important field of study, not only in research, but also in undergraduate optics and photonics education and training. Beyond the study of classical and quantum optics, it is important for students to learn about how the flow of light can be manipulated on a nanoscale level, and used in applications such as telecommunications, imaging, and medicine. 

1. Description

2. Why

3. How

4. Applications

5. Future Trends

6. Related Links

Description

Nanophotonics, which combines the capabilities of nanoscience and technology with photonics, has emerged as a new and important field of study in its own right, encompassing the study of new optical interactions, materials, fabrication techniques, and architectures, including the exploration of natural and synthetic, or artificially engineered, structures such as photonic crystals, holey fibers, quantum dots, sub-wavelength structures, and plasmonics.

  • The domain of nanoscale science and technology lies between the familiar classical world of macroscopic objects and the quantum mechanical regime of atoms and molecules.
  • This area of nanoscience, called nanophotonics, is defined as “the science and engineering of light-matter interactions”.
  • Photonics on silicon has been suggested since the 1970’s, and previous light-beam switching devices on silicon have been demonstrated.
  • They were excessively large (by microchip standards) or required that the beam of light that does the switching be very high-powered.

It is only in the last few years, however, with the advancement of fabrication techniques that sub-micron-size photonic structures have been realized enabling some of the traditional limitations of silicon photonics to be overcome.

Why

Nanostructures can have unique, controllable, and tunable optical properties that arise from their nanoscale size and from the fact that they are smaller than the wavelength for which they are designed.

  • Both the properties of the nanostructures and their organization into large-scale materials, which may be ordered on the scale of the wavelength, are important for determining the optical response.
  • The sub-wavelength optical confinement and low optical loss of nanophotonic devices dramatically enhances the interaction between light and matter within these structures.
  • Nanophotonic devices are combined with an efficient optical coupling channel
  • Nonlinear optical behavior can be observed at low power levels in weakly-nonlinear materials.

How

The areas of nanophotonics are characterized by their different physical nanoscale phenomena and the scale (relative to a wavelength) of the modulation of the index of refraction in the nanoscale material or system. Following are the four areas of nanophotonics:

  • Photonic crystals— in which the spatial index modulation is on the order of a wavelength.
  • Metamaterials— in which the structural elements are much smaller than the wavelength, permitting an effective medium approach to the optical properties.
  • Plasmonics—in which manipulation of light at the nanoscale is based on the properties of surface plasmons arising from metal free-electron response (negative permeability).
  • Confined semiconductor structures— whose physics is driven by reduced dimensionality and quantum confinement.

One-dimensional nanoscale structures, such as multilayer optical coatings and distributed Bragg reflectors, have long been staples of optical design and engineering.The ability to dramatically alter the optical properties of virtually any material by suitable combinations of “top-down” and “bottom-up” fabrication technologies, enhancing the capabilities for signaling, switching, detection, and concealment.The optical switch is based on a ring resonator, a device already familiar to photonics researchers. When a straight waveguide is placed tangent to a ring-shaped waveguide, photons traveling along the straight waveguide are diverted into the ring.A similar effect can be used in a straight waveguide, but requires fairly long distances. Because light travels many times around the ring the scattering effect is enhanced and the signal can be controlled in a very small space.

Applications

Nanophotonics-based systems are expected to have far-reaching applications in both military and commercial markets, including the following:

  • Power, weight, and volume savings with higher speed and functionality on all military systems, including but not limited to uncooled, infrared sensors and night vision; ultrasecure communications and quantum information processing; photovoltaic power sources          
  • External photonic communications between nanophotonic-enabled silicon chips, with widespread application likely within a few years, particularly for computers and microprocessors;
  • Internal photonic communication within chips, enabling militarily significant functions, 
  • Potentially significant power savings within computing systems.
  • Multicore processor interconnects leading to advanced computational applications such as image recognition;
  • Heat-assisted magnetic recording using plasmonic focusing, which is part of the roadmap of the hard-disk drive industry.
  • Biosensing systems based on fluorescent molecules and/or quantum dots and on plasmonic effects—for example, surface-enhanced Raman scattering—for use in medical in-field diagnostics, bioagent detection, and bioremediation.

Future Trends

Indeed, the optical properties of nanomaterials can be tailored for important commercial and defense applications, such as compact photoelectric power sources; efficient and tunable light sources, detectors, filters, waveguides, and modulators; high-speed all-optical switches; environmental (both chemical and biological) sensors; next-generation classical and quantum computation; and biophotonic medical diagnostics and therapeutics.With these developments come new and exciting opportunities for students at the undergraduate level to learn about how the flow of light can be manipulated on a nanoscale level, and used in critical applications that range from telecommunications and imaging, to medicine, healthcare, and environmental sensing. Such an exposure can provide breadth in the overall educational experience, as well as a heightened awareness of the pervasive role that this interdisciplinary field plays in today’s society.Profound advances in the control of single photons, the increased efficiency of photonic devices, and the interaction of photons with matter have been realized over the past 15 to 20 years. The pace of innovation and implementation will only increase with the availability of novel nanophotonics building blocks, the development of enabling technologies, and the insights gained by characterizing nanophotonics devices and phenomena.

Keywords

Nanophotonics, optical signal processing, optical near-field, information processing, nanophotonic computing

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