Metal-Coated Nanocylinder Cavity for Broadband Nonclassical Light Emission

A novel metal-coated nanocylinder-cavity architecture fully compatible with III-V GaInAs technology and benefiting from a broad spectral range enhancement of the local density of states is proposed as an integrated source of nonclassical light. Because of a judicious selection of the mode volume, the cavity combines good collection efficiency ($\approx 45\%$), large Purcell factors ($\approx 15$) over a 80 nm spectral range, and a low sensitivity to inevitable spatial mismatches between the single emitter and the cavity mode. This represents a decisive step towards the implementation of reliable solid-state devices for the generation of entangled photon pairs at infrared wavelengths.

Figure 1

(a) Cross section of the metal-coated nanocylinder showing the main physical quantities involved in the FP model. (b) Top-view including the $|E_x{|}^2$ field profile of the fundamental ${\mathrm{TE}}_{11}$ mode, calculated for $a=100\mathrm{nm}$, $e=5\mathrm{nm}$, and ${\lambda }_0=950\mathrm{nm}$. (c) Effective index $n_{\mathrm{eff}}$ of the ${\mathrm{TE}}_{11}$ mode for ${\lambda }_0=950\mathrm{nm}$.

Figure 2

Main physical quantities of the FP model as a function of the cylinder radius $a$ for ${\lambda }_0=950\mathrm{nm}$ and $e=5\mathrm{nm}$. (a) Reflectance of the top and bottom interfaces. (b) Out-coupling efficiency of the fundamental mode. (c) Purcell factor. The inset shows the $H$ and $h_2$ that maintain the FP phase-matching resonance condition as $a$ varies. (d) Extraction efficiency for several $\theta$. In (c) and (d), circles are obtained with the 3D FEM.

Figure 3

Spectral performance of the nanocavity for $a=100\mathrm{nm}$, $e=5\mathrm{nm}$, $H=65\mathrm{nm}$, and $[h_1,h_2]=[57,8]\mathrm{nm}$. (a) Purcell factor. (b) Extraction efficiency for several $\theta$ [same markers and colors as in Figs. 2c, 2d]. The efficiency drop predicted with the FEM at $\lambda <850\mathrm{nm}$ is due to a resonance of the ${\mathrm{TE}}_{21}$ mode, near its cutoff at $\lambda =750\mathrm{nm}$.

Figure 4

Influence of the off-axis dipole location $a_0$ at ${\lambda }_0=950\mathrm{nm}$. (a) Dotted (red) and dashed (blue) curves: SE rate of the radial and orthoradial dipoles into the ${\mathrm{TE}}_C$ mode. Thin, gray solid curve: SE rate of the radial dipole into the ${\mathrm{TM}}_C$ mode. Black-solid curve: total SE rate of the radial dipole due to radiation into both the ${\mathrm{TE}}_C$ and ${\mathrm{TM}}_C$ modes. (b) Fidelity of entanglement (0.85 threshold is indicated). (c) Probability to collect a photon from the ${\mathrm{TE}}_C$ [(red) dotted] and ${\mathrm{TM}}_C$ [(blue) dashed] modes for $\theta =90°$. (d) Far-field radiation patterns of the ${\mathrm{TE}}_C$ and ${\mathrm{TM}}_C$ modes.