Fig. 1. (a) Schematic diagram of an NW scanned across a PPC nanocavity along the lattice’s $\mathrm{\Gamma }-\mathrm{M}$ direction. (b) Intensity distribution of the cavity’s fundamental mode. (c) $\mathrm{\Sigma }{P}_x$, $\mathrm{\Delta }\lambda$, and $\eta$ of the NW-PPC nanocavity versus the NW’s positions. (d) $Q$ factor, $V_{\mathrm{mode}}$, and $\eta Q/V_{\mathrm{mode}}$ of the NW-PPC nanocavity versus the NW’s positions, where the red dashed lines indicate $Q_0$ and $V_{\mathrm{m}\mathrm{ode}0}$ of the bare nanocavity.

Fig. 2. Mode intensity profiles and polarizations of electrical fields for NW positions of (a) 0 nm, (b) 180 nm, (c) 360 nm, and (d) 540 nm, where the intensities and polarizations are denoted by the colors and pink arrows.

Fig. 3. Simulation results when the NW scans along the lattice’s $\mathrm{M}-\mathrm{K}$ direction. (a) $\mathrm{\Sigma }{P}_y$, $\mathrm{\Delta }\lambda$, and $\eta$ of the NW-PPC nanocavity versus the NW’s position. (b) $Q$ factor, $V_{\mathrm{mode}}$, and $\eta Q/V_{\mathrm{mode}}$ of the NW-PPC nanocavity versus the NW’s position, where the red dashed line indicates the $Q_0$ factor and $V_{\mathrm{mode}0}$ of the bare nanocavity. (c1)–(c4) Mode intensity profiles and polarizations of electrical fields when the NW locates at (c1) $y=0\mathrm{nm}$, (c2) 160 nm, (c3) 280 nm, and (c4) 560 nm, respectively.

Fig. 4. Simulation results of coupling between the NW and the cavity’s second-order mode. (a) Mode intensity profile (top panel) and polarizations (bottom panel) of the cavity’s second-order mode. (b), (c) $\mathrm{\Delta }\lambda$, $Q$ factor, $\eta$, and $\eta Q/V_{\mathrm{mode}}$ of the second-order mode versus the NW position when it is scanned along the (b) $\mathrm{\Gamma }-\mathrm{M}$ and (c) $\mathrm{M}-\mathrm{K}$ directions. The red dashed line indicates the $Q_0$ factor of the bare nanocavity.

Fig. 5. Experiment results of mode couplings in NW-PPC nanocavities when moving the NW along the lattice’s $\mathrm{M}-\mathrm{K}$ direction. (a) AFM images of the NW-PPC nanocavities when the ${\mathrm{Al}}_{0.2}{\mathrm{Ga}}_{0.8}\mathrm{As}$ NW is gradually moved close to the cavity center. The scale bar corresponds to 500 nm. (b) The measured (dotted lines) and Lorentzian fitted (solid lines) reflection spectra of the (b1) fundamental and (b2) second-order resonant modes of the NW-PPC nanocavities with different NW positions. (c) $\mathrm{\Delta }\lambda$ of the (c1) fundamental and (c2) second-order modes versus the NW positions. (d) $Q$ factors of the (d1) fundamental and (d2) second-order modes versus the NW positions, where the black (red) dashed lines represent the simulated (measured) $Q_0$ factor.