Magnetic plasmonic metamaterials in actively pumped host medium and plasmonic nanolaser

We consider plasmonic nanoantennas immersed in active host medium. Specifically shaped metal nanoantennas can exhibit strong magnetic properties in the optical spectral range due to the excitation of magnetic plasmon resonance. A case when a metamaterial comprising such nanoantennas can demonstrate both ``left handiness'' and negative permeability in the optical range is considered. We show that high losses predicted for optical ``left-handed'' materials can be compensated in the gain medium. Gains required to achieve local generation in such magnetic active metamaterials are calculated for real metals. We propose plasmonic nanolaser, where the metal nanoantenna operates similar to a resonator. The size of the proposed plasmonic laser is much smaller than the wavelength. Therefore, it can serve as a very compact source of electromagnetic radiation.