One-sided composite cavity on an optical nanocapillary fiber

TL;DR

The work tackles the challenge of achieving high-efficiency, unidirectional emission into a single optical-capillary-guided mode from a quantum emitter. It introduces a composite one-sided cavity by integrating an asymmetric defect-mode grating with an optical nanocapillary fiber and analyzes the system with 3D FDTD methods. Key findings include a maximum channeling efficiency of about 0.8, a best quality factor of approximately 1.93×10^4, a finesse around 240, and a one-pass loss near 1.3%, with an effective cavity length of about 25 μm, accessible under various coupling regimes. The design demonstrates potential for fiber-based deterministic single-photon sources and outlines practical paths for experimental realization and material-index enhancements to further boost efficiency.

Abstract

We numerically report a one-sided cavity on an optical nanocapillary fiber (NCF) using a composite cavity. The composite cavity is formed by combining an optical NCF and an asymmetric defect mode grating. We design the cavity to realize the maximum channeling efficiency of up to 80% into one-sided NCF-guided modes while operating from under- to critical- and overcoupling regimes. For the maximum channeling efficiency case, we found the best quality factor, finesse, and one-pass loss of the cavity are 19354, 240, and 1.3%, respectively. The present platform may open a novel route for designing fiber-based deterministic single-photon sources in quantum technologies.

Figures (3)

• Figure 1: A conceptual diagram of a one-sided composite cavity. The cavity is realized by combining an asymmetric defect mode grating (ADMG) with an optical nanocapillary fiber (NCF), and $y$-polarized single quantum emitter (SQE) placed at the cavity anti-node position. The inset shows the side view of the cavity with the designed parameters as mentioned in the text. $\kappa_{in}$ and $\kappa_{sc}$ are the input coupling rate and scattering rate (intra-cavity loss rate) of the cavity, respectively.
• Figure 2: Depict the dependency of channeling efficiency ($\eta$, blue spheres), Purcell factor ($F_p$, red spheres) on (a) output ($N_{out}$) slat number while input ($N_{in}$) slat number is fixed at 200 and (b) input ($N_{in}$) slat number while output ($N_{out}$) slat number is fixed at 400.
• Figure 3: (a), (b) and (c) are the typical cavity reflection spectra for $x$ (blue trace)- and $y$ (red trace)-polarized input mode sources for the input slat number ($N_{in}$) at 190 (over), 290 (critical), and 340 (under) for the fixed output slat number ($N_{out}$) at 400, respectively. (d) and (e) are the on-resonance cavity's reflectivity ($R_0$) for $x$ (blue spheres) and $y$ (red spheres)-polarized input mode sources, respectively. The top $x$-axes represent the corresponding $N_{in}$-values. The solid blue (red) line fits the data for $x$ ($y$)-pol. The insets show the normalized electric field intensity distribution at the anti-node ($\Delta z$= 0 nm) of the cavity, and white dotted lines represent the NCF surfaces. (f) depicts the variation of channeling efficiency ($\eta$, red spheres), purcell factor ($F_p$, black spheres) with the $\kappa$-values and the corresponding $N_{in}$-values are shown in the top $x$-axis.