We experimentally demonstrate the enhancement of the spontaneous emission rate of GaAs quantum wells embedded in rolled-up metamaterials. We fabricate microtubes whose walls consist of alternating Ag and (In)(Al)GaAs layers with incorporated active GaAs quantum-well structures. By variation of the layer thickness ratio of the Ag and (In)(Al)GaAs layers we control the effective permittivity tensor of the metamaterial according to an effective medium approach. Thereby, we can design samples with elliptic or hyperbolic dispersion. Time-resolved low temperature photoluminescence spectroscopy supported by finite-difference time-domain simulations reveal a decrease of the quantum well's spontaneous emission lifetime in our metamaterials as a signature of the crossover from elliptic to hyperbolic dispersion.

We experimentally demonstrate the enhancement of the spontaneous emission rate of GaAs quantum wells embedded in rolled-up metamaterials. We fabricate microtubes whose walls consist of alternating Ag and (In)(Al)GaAs layers with incorporated active GaAs quantum-well structures. By variation of the layer thickness ratio of the Ag and (In)(Al)GaAs layers we control the effective permittivity tensor of the metamaterial according to an effective medium approach. Thereby, we can design samples with elliptic or hyperbolic dispersion. Time-resolved low temperature photoluminescence spectroscopy supported by finite-difference time-domain simulations reveal a decrease of the quantum well's spontaneous emission lifetime in our metamaterials as a signature of the crossover from elliptic to hyperbolic dispersion.

We experimentally demonstrate that hybrid plasmon-photon modes exist in a silver-coated glass bottle resonator. The bottle resonator is realized in a glass fiber with a smoothly varying diameter, which is subsequently coated with a rhodamine 800-dye doped acryl-glass layer and a 30 nm thick silver layer. We show by means of photoluminescence experiments supported by electromagnetic simulations that the rhodamine 800 photoluminescence excites hybrid plasmon-photon modes in such a bottle resonator, which provide a plasmon-type field enhancement at the outer silver surface and exhibit quality factors as high as 1000.

We demonstrate gain in a three-dimensional metal/semiconductor metamaterial by the integration of optically active semiconductor quantum structures. The rolling-up of a metallic structure on top of strained semiconductor layers containing a quantum well allows us to achieve a three-dimensional superlattice consisting of alternating layers of lossy metallic and amplifying gain material. We show that the transmission through the superlattice can be enhanced by exciting the quantum well optically under both pulsed or continuous wave excitation. This points out that our structures can be used as a starting point for arbitrary three-dimensional metamaterials including gain.Metamaterials are composite materials made of artificial building blocks whose size and lattice constant is small compared to the wavelength of the transmitted light. An advantage of metamaterials compared to conventional natural materials is that their properties can be tailored by varying the size and shape of the artificial building blocks. In particular using metallic structures, negative index of refraction in the near-infrared and visible regime had been realized using metallic split ring resonators [1] or fishnet structures [2][3][4]. To prove bulk properties and use metamaterials for devices one has to achieve a three-dimensional structure which is usually planar lithographically defined and fabricated sequentially until the desired thickness is reached [5][6][7]. All these metamaterials are hampered by absorption which is caused by ohmic losses in the metallic compound or, in other words, by the finite imaginary part of the dielectric function of the metal. A proposal to compensate these losses is to integrate a gain medium into the metamaterial which amplifies the transmitted light [8] like, e.g. dye [9] or semiconductor quantum structures [10,11]. Recently it has been shown that a dye surrounding the metallic structures can compensate the losses in a metamaterial [12]. In contrast to dyes, semiconductor quantum structures exhibit no photo bleaching, a higher damage threshold and the possibility of electrical pumping. Investigations on two-dimensional planar systems show that metallic structures can be coupled to a quantum structure and partially compensate the ohmic losses [13][14][15].In this letter, we present three-dimensional radial metamaterials consisting of alternating layers of metal structures and amplifying semiconductor quantum structures. For the fabrication we utilize the concept of selfrolling strained layers [16-18] which we recently extended to strained metal/semiconductor metamaterials with a possible application as a hyperlens [19,20]. Here we investigate a novel structure with active quantum wells integrated into the semiconductor layer. As a result we ob- tain a truly three-dimensional metamaterial containing optical amplifiers which enhance the light transmission by stimulated emission. We present transmission measurements which show a transmission enhancement of about 5 % under optical continuous wave (cw) excitatio...

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