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We consider plasmonic nanoantennas immersed in an active host medium. Specifically shaped metal nanoantennas can exhibit strong magnetic properties in the optical spectral range due to excitation of the magnetic plasmon resonance. A case in which a metamaterial comprising such nanoantennas can demonstrate both left handedness and negative permeability in the optical range is discussed. We show that high losses predicted for optical left-handed materials can be compensated in the gain medium. Gain allows one to achieve local generation in magnetically active metamaterials. We propose a plasmonic nanolaser where the metal nanoantenna operates in a fashion similar to a resonator. The size of the proposed plasmonic laser is much smaller than the light wavelength. Therefore, it can serve as a very compact source of coherent electromagnetic radiation and can be incorporated in future plasmonic devices.
Extending the range of electromagnetic properties of naturally occurring materials motivates the development of artificial metamaterials. For example, metamaterials with artificial microwave magnetism were known since the beginning of the 1950s. It has been demonstrated recently that metamaterials may exhibit such exotic properties as negative dielectric permittivity, negative magnetic permeability, and even both. The double-negative case of Re ε < 0 and Re μ < 0 is often referred to as a left-handed material (LHM). Situations in which a negative refractive index can be realized in practice are particularly interesting because of the possibility of a âperfectâ lens with subwavelength spatial resolution. In addition to the superresolution not being limited by classical diffraction, many unusual and sometimes counterintuitive properties of negative refraction index materials (NIMs) make them very promising for applications in resonators, waveguides, and other microwave and optical elements. Negative refraction and subwavelength imaging have been demonstrated in the microwave and RF regimes.
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