Cavity Quantum Electrodynamics on a Nanofiber Using a Composite Photonic Crystal Cavity

We demonstrate cavity QED conditions in the Purcell regime for single quantum emitters on the surface of an optical nanofiber. The cavity is formed by combining an optical nanofiber and a nanofabricated grating to create a composite photonic crystal cavity. By using this technique, significant enhancement of the spontaneous emission rate into the nanofiber guided modes is observed for single quantum dots. Our results pave the way for enhanced on-fiber light-matter interfaces with clear applications to quantum networks.

Figure 1

(a) Conceptual diagram of the device and design parameters. (b) Scanning electron microscope image of the device. (c) Experimental setup used to characterize the optical response of the CPCC. SC, ILP, and FTSA denote the supercontinuum source, in-line polarizer, and Fourier transform spectrum analyzer, respectively. (d) Experimental setup for PL intensity spectrum measurements. The inset depicts the azimuthal position defined by angle $\varphi$ of the QDs (red dots). Corr., NPS, OL, HWP, PBS, and OMA denote the correlator, nanopositioning stage, objective lens, half wave plate, polarizing beam splitter, and optical multichannel analyzer, respectively. The $x$-, $y$-, and $z$-axes are defined as shown.

Figure 2

(a) Simulated electric field intensity inside the CPCC for the $y$-mode. The inset shows an expanded view of the central region of the cavity. White horizontal lines mark the position of the edges of the nanofiber. (b),(c) Simulated and measured transmission spectra, respectively, for the $x$ (blue line) and $y$-modes (red line).

Figure 3

(a) Simulations of PL intensity spectra for $x$- (blue line), $y$- (red line), and $z$-polarized (green line) dipole sources. The inset shows the average of the PL intensity spectra. (b) The dependence of the EF on the position $\mathrm{\Delta }z$ of the dipole source in the cavity. Circles show results for $\varphi =0°$, and triangles show results for $\varphi =90°$.

Figure 4

(a) PL intensity spectrum showing the $x$- and $y$-modes (left and right peak, respectively). (b) Measured PL intensity spectra for three different single QDs. The inset shows a typical normalized photon correlation signal. (c) EFs for single QDs in the CPCC and cavity $Q$ factors. Red diamonds and green squares with error bars show measured EFs, while black circles show corrected EFs. The inset shows experimentally measured $Q$ factors for the $y$-mode cavity transmission peaks (linear fit shown by a solid line).