Guest Editorial: Nanophotonics for Communications

The communication industry has been the major driving force behind the extraordinary progress made in photonics that contributed to an age of information explosion over the past two decades. In the recent past, scientific breakthroughs have brought tremendous momentum to this field of research and we have observed an outbreak of interest in nanoscale materials and devices with revolutionary applications in both electronics and photonics. Enormous progress has been made in the field of nanophotonics based on high-index contrast waveguides, photonic crystals, plasmonics, nanoheteroepitaxy, and low-dimensional materials and devices. Extremely sharp curves and bends along with sophisticated splitters have also been demonstrated, thereby allowing a high level of device integration. Different materials have been explored ranging from polymers to semiconductors on a variety of substrates for both passive and active photonic devices. Applications for these devices include telecom, sensing, on-chip and chip-to-chip interconnects, and Si photonics, among others. Subsequent to more than a decade of research, the applications of nanophotonics in communications are progressively becoming a technological challenge rather than a field of fundamental research. Therefore, it is not an overstatement that nanophotonics is now becoming ubiquitous in the field of computer and communication technologies. This special section, with seven invited papers, attempts to highlight some of the significant popular topics in nanophotonics for communication and has contributions from several renowned experimentalists as well as theorists, who have presented the necessary physical understanding along with the state-of-the-art review of active and passive nanoscale materials and devices for communication applications. In the first paper, Gerken and Nazirizadeh address the use of one-, two-, and threedimensional photonic crystals and related structures to engineer the spontaneous emissionradiation pattern as well as the relaxation time. The authors focus on enhancing the performance of LEDs, lasers, and single-photon sources that may be applied in future communication devices. The performance of these optoelectronic devices is largely governed by the spontaneous emission properties, which are not inherent to an emitter but may be engineered to improve device performance [1]. The far-field radiation pattern of LEDs, for example, may be designed to funnel more than 80% of the generated photons into a divergence angle of just ±30 deg by using defects in two-dimensional photonic crystals [2]. Photonic crystal defect-based lasers exhibit far increased modulation speeds with response times on the order of a few picoseconds [3], and single quantum dots in two-dimensional photonic crystals are applicable as efficient single-photon sources [4]. The current size of optoelectronic circuits is several orders of magnitude larger, in physical dimensions, than their ordinary electronic counterparts. State-of-the-art commercial electronic devices are fabricated with feature sizes in the range of tens of nanometers. On the other hand, optical devices can reach a theoretical size limit on the order of the wavelength, if sophisticated techniques, such as those based on photonic crystals, are used. Thus, the packing density of optical devices remains low. Another notable difference is the difficulty in designing optical devices with dimensions much smaller than the wavelengths involved. Journal of Nanophotonics, Vol. 2, 021799 (14 February 2008)