Young’s Type Interference for Probing the Mode Symmetry in Photonic Structures

A revisited realization of the Young’s double slit experiment is introduced to directly probe the photonic mode symmetry by photoluminescence experiments. We experimentally measure the far field angular emission pattern of quantum dots embedded in photonic molecules. The experimental data well agree with predictions from Young’s interference and numerical simulations. Moreover, the vectorial nature of photonic eigenmodes results in a rather complicated parity property for different polarizations, a feature which has no counterpart in quantum mechanics.

Figure 1

Scheme of the emission patterns of two coupled modes ${\mathbf{E}}_{+}(\mathbf{r})$ (left) and ${\mathbf{E}}_{-}(\mathbf{r})$ (right) in a photonic microcavity molecule. The rhombs indicate the electric field distributions of the two modes, with a color scale to emphasize the positive (red) and negative (blue) amplitude. Red (blue) dashed lines indicate the constructive (destructive) optical paths in the far field emission patterns.

Figure 2

Single $D2$ cavity. (a) PL spectra in the $x$ (black line) and $y$ (red line) polarization channels. (b) SEM image. (c)–(e) Electric field FDTD NF maps: (c) $x$ component of $M1$, (d) $x$ component of $M2$, (e) $y$ component of $M2$. (f)–(h) Experimental PL FF intensity $k$ patterns : (f) $x$ polarization of $M1$, (g) $x$ polarization of $M2$, (h) $y$ polarization of $M2$. (i)–(k) FDTD FF intensity $k$ pattern: (i) $x$ polarization of $M1$, (j) $x$ polarization of $M2$, (k) $y$ polarization of $M2$. SEM and NF images are $1.5\mu \mathrm{m}\times 2.0\mu \mathrm{m}$. In the NF maps red (blue) color indicates the positive (negative) amplitude. The FF patterns cover the whole external solid angle and the white circles are the experimental cone of view.

Figure 3

Vertically aligned photonic molecule. (a) PL spectrum (red line) compared with the PL spectrum of the single $D2$ MC (blue line), the inset shows the SEM image. (b) and (c) Experimental PL FF intensity $k$ patterns of $P1$ and $P2$. (d) and (e) Young’s predictions of “+” and “-” modes. (f)and (g) FDTD FF intensity $k$ patterns of $P1$ and $P2$. The FF patterns cover the whole external solid angle and the white circles are the experimental cone of view.

Figure 4

Horizontally aligned photonic molecule. (a) PL spectrum (red line) compared with the PL spectrum of the single $D2$ MC (blue line), the inset shows the SEM image. (b)–(e) Experimental PL FF intensity $k$ patterns: (b) and (c) $x$ polarization of $P3$ and $P4$; (d) and (e) $y$ polarization of $P3$ and $P4$. (f)–(i) Young’s predictions: (f) and (g) $x$ polarization of “-” and “+” modes; (h) and (i) $y$ polarization of “-” and “+” modes. (j)-(m) FDTD FF intensity $k$ patterns. (j) and (k) $x$ polarization of $P3$ and $P4$; (l) and (m) $y$ polarization of $P3$ and $P4$. The FF patterns cover the whole external solid angle and the white circles are the experimental cone of view.

Figure 5

Electric field FDTD NF maps for the coupled modes. The color scale indicates the positive (red) and negative (blue) amplitude; (a) and (b) $x$ component of $P1$ and $P2$ for vertical coupling; the maps are $1.4\mu \mathrm{m}\times 3.5\mu \mathrm{m}$; (c) and (d) $x$ component of $P3$ and $P4$ for horizontal coupling; (e) and (f) $y$ component of $P3$ and $P4$ for horizontal coupling; the maps are $2.3\mu \mathrm{m}\times 1.7\mu \mathrm{m}$.