Lifetime reduction of a quantum emitter with quasiperiodic metamaterials

Enhancement of light-matter interaction of a quantum emitter with subwavelength quasiperiodic metamaterials is proposed and demonstrated. The quasiperiodic metamaterials consist of subwavelength metal-dielectric multilayers, which are arranged into a Fibonacci lattice. The influence of Fibonacci metamaterials (FM) on the dipole emission is analyzed with a semiclassical model. The local density of states near FM is evaluated and a characteristic mode in higher wave numbers is revealed; a strong enhancement of the decay rate was predicted. A lifetime measurement is carried out and a reduction of lifetime of quantum dots on the surface of FM is observed. The enhancement of light-matter interaction arises from the localized latticelike state inherent for self-similar quasiperiodic order.

Figure 1

Schematics of the metamaterial structure and arrangement of the dipole. (a) Metamaterial structures composed of silver and silica layers. The layers of Fibonacci metamaterials (FM) are aligned in the order of the Fibonacci lattice and the thickness of each layer is 20 nm (left). The layers of periodic metamaterials (PM) are stratified periodically and the period is 40 nm (right). Filling factor $f$ of PM is set to be the same as that of FM. (b) The configuration of our calculation. The dipole is placed above the material surface. The reflected field of radiation from dipole at surface affects the radiation properties of dipole.

Figure 2

Calculation of LDOS spectra of the dipole near the metamaterials. Red line is the result for FM of sixth generation. Blue line is the result for PM of six periods. Horizontal axis corresponds to in-plane wave number $u$ of dipole normalized by free space wave number. Significant peak is seen at $u=3.3$ for FM.

Figure 3

Electric field intensity distribution of LLS calculated by a transfer matrix method. The vertical axis has a logarithmic scale. The horizontal axis corresponds to the stratified direction. The shaded areas are dielectric layers. (a) Result by ignoring metallic loss. (b) Result with realistic loss [$\mathrm{Im}\left({\varepsilon }_{\mathrm{Ag}}\right)=1.12$] included. Electromagnetic energy of LLS is localized near the surface of FM.

Figure 4

Cumulative LDOS spectra of Fig. 2 evaluated by Eq. (10). Red line is a result for FM; blue line is a result for PM. Cumulative LDOS for FM drastically increases at $u=3.3$, which corresponds to LLS.

Figure 5

Photographs of fabricated samples (left) and reflection spectra at normal incidence (right). The effective plasma frequency of multilayer metamaterials shifts to the red side.

Figure 6

Experimental setup for a lifetime measurement of quantum dots. A blue (400 nm) pulse generated by SHG of mode-locked Ti:sapphire laser was used for excitation. Fluorescence from quantum dots was collected by an objective lens, and the time resolved lifetime measurement was carried out by a streak camera.

Figure 7

Time resolved fluorescence from quantum dots near metamaterials. Vertical axis corresponds to the normalized intensity of fluorescence in a logarithmic scale. The red circle, blue triangle, and black cross point correspond to the experimental data for FM, PM, and silver samples, respectively. Lines are the fitting results, and the estimated lifetime is indicated in the legend.