The so-called PT symmetric devices, which feature ε((-x)) = ε((x))* associated with parity-time symmetry, incorporate both gain and loss and can present a singular eigenvalue behaviour around a critical transition point. The scheme, typically based on co-directional coupled waveguides, is here transposed to the case of variable gain on one arm with fixed losses on the other arm. In this configuration, the scheme exploits the full potential of plasmonics by making a beneficial use of their losses to attain a critical regime that makes switching possible with much lowered gain excursions. Practical implementations are discussed based on existing attempts to elaborate coupled waveguide in plasmonics, and based also on the recently proposed hybrid plasmonics waveguide structure with a small low-index gap, the PIROW (Plasmonic Inverse-Rib Optical Waveguide).
Coupling plasmonics and silicon photonics is the best way to bridge the size gap between macroscopic optics and nanodevices in general and especially nanoelectronic devices. We report on the realization of key blocks for future plasmonic planar integrated optics, nano-optical couplers, and nanoslot waveguides that are compatible both with the silicon photonics and the CMOS microelectronics. Copper-based devices provide for very efficient optical coupling, unexpectedly low propagation losses and a broadband sub-50 nm optical confinement. The fabrication in a standard frontline microelectronic facilities hints broad possibilities of hybrid opto-electronic very large scale integration.
We show that interfering surface plasmon polaritons can be excited with a focused laser beam at normal incidence to a plane metal film. No protrusions or holes are needed in this excitation scheme. Depending on the axial position of the focus, the intensity distribution on the metal surface is either dominated by interferences between counterpropagating plasmons or by a two-lobe pattern characteristic of localized surface plasmon excitation. Our experiments can be accurately explained by use of the angular spectrum representation and provide a simple means for locally exciting standing surface plasmon polaritons.
We report on the fabrication of monolithic omnidirectional mirrors based on one-dimensional photonic crystals. The mirrors are comprised of chirped and unchirped multiple layers of microporous silicon. Porosities have been chosen to achieve an optimal low refractive index nL∼1.5 and a high refractive index nH∼2.55. Unchirped structures, centered in the near-infrared, exhibit an omnidirectional reflection band of 100 nm, in agreement with the calculated photonic band structure. Chirped structures exhibit an enlarged omnidirectional stop band (340 nm). Given the possibility of easily tailoring the optical thickness of porous silicon, this material is shown to be very practical for engineering omnidirectional mirrors.
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