Figure 1

Schematic of frequency conversion using a quantum emitter coupled to a Sagnac interferometer. (a) Energy diagram of a $\Lambda$-type three-level quantum emitter with transition frequencies ${\omega }_{13}={\omega }_3-{\omega }_1$ and ${\omega }_{23}={\omega }_3-{\omega }_2$. The left diagram corresponds to frequency down-conversion, and the right diagram corresponds to up-conversion. (b) Sagnac interferometer coupled to a three-level quantum emitter. (c) Supplementary external routing components. (Left) A waveguide coupling component. (Right) A broadband optical circulator.Reuse & Permissions

Figure 2

Transmission spectra for an incoming photon of frequency $\omega$ when the atom is initially in state $|1⟩$. ${\Gamma }_1={\Gamma }_2$ is assumed.Reuse & Permissions

Figure 3

Frequency conversion efficiency $P_c$ for several different types of incoming photonic waves. (a) $P_c$ for a Gaussian input pulse. (b) $P_c$ for ${\mathrm{sech}}^2$, Gaussian, chirped Gaussian, and square input pulses of equal intensity FWHM time duration. $\alpha =1$ for all cases.Reuse & Permissions

Figure 4

Frequency down-conversion for a Gaussian input pulse (denoted by solid blue curves). (a) Emitter directly coupled to a one-dimensional waveguide. Dashed (dotted) blue curve: Transmitted (reflected), frequency-unshifted pulse; dashed (dotted) red curve: transmitted (reflected), frequency-shifted pulse. (b) Sagnac interferometer geometry; phase shifter off ($\theta =0$). Dashed blue curve: Frequency-unshifted output; dashed red curve: frequency-shifted output. (c) Sagnac interferometer geometry; phase shifter on ($\theta =\pi$). Dashed blue curve (overlapping with solid blue): Frequency-unshifted output; the frequency-shifted portion is so small as to not be visible. For all cases, the input is a Gaussian pulse with intensity FWHM time duration $\tau =0.5\mathrm{ns}$ and center wavelength $\lambda =819\mathrm{nm}$, on resonance with the $|1⟩\leftrightarrow |3⟩$ transition. Quantum emitter parameters correspond to the $D^0\mathrm{\text{−}}D{X}^0$ transition in a GaAs quantum dot: coupling parameters [28] ${\Gamma }_1={\Gamma }_2=2\pi \times {10}^9{\mathrm{s}}^{-1}$; intrinsic damping [29] ${\gamma }_c=2\pi \times {10}^6{\mathrm{s}}^{-1}$.Reuse & Permissions