Polarized and Bright Telecom C-Band Single-Photon Source from InP-Based Quantum Dots Coupled to Elliptical Bragg Gratings

Abstract

Bright, polarized, and high-purity single-photon sources in telecom wavelengths are crucial components in longdistance quantum communication, optical quantum computation, and quantum networks. Semiconductor InAs/InP quantum dots (QDs) combined with photonic cavities provide a competitive path, leading to optimal single-photon sources in this range. Here, we demonstrate a bright and polarized single-photon source operating in the telecom C-band based on an elliptical Bragg grating (EBG) cavity. With a significant Purcell enhancement of 5.25 ± 0.05, the device achieves a polarization ratio of 0.986, a single-photon purity of g 2 (0) = 0.078 ± 0.016, and a single-polarized photon collection efficiency of ∼24% at the first lens (NA = 0.65) without blinking. These findings suggest that C-band QD-based single-photon sources are potential candidates for advancing quantum communication.

Efficient, Indistinguishable Telecom C-Band Photons using a Tapered Nanobeam Waveguide

“…From this fit, we determined the quantum dot saturation count rates to be 575 ± 5 Kcps (cps: counts per second). The count rates could be improved by incorporating the dot into a cavity and using the Purcell effect to radiatively enhance the emission. , …”

“…We achieved C-band single photons with a count rate of 575 ± 5 Kcps, g (2) (0) = 0.015 ± 0.003, a two-photon interference visibility of 0.84 ± 0.06, and a photon coherence time of 450 ± 20 ps using above-band excitation. The efficiency of the device could be further improved by employing resonant cavities that increase radiative efficiency through the Purcell effect . Moreover, utilizing resonant excitation, quasi-resonant excitation, and nanoscale focus pinspot techniques could further reduce the g (2) (0) value and improve indistinguishability by suppressing the time jitter induced by relaxation to the exciton ground state .…”

“…The quantum dots were formed by first growing a 1.1 monolayer of InAs at a growth temperature of 510 °C. This layer was then annealed at the growth temperature for 120 s to facilitate the ripening technique, , enabling control over the density and emission wavelength around 1550 nm. This process resulted in a quantum dot layer with densities between 10 and 50 μm –2 .…”

“…A telecom single-photon source operating around 1,550 nm (C-band) is essential for fiber-based quantum communication networks to minimize transmission loss in the silica fiber. Various approaches have been explored to realize single-photon sources within this spectral window, including spontaneous parametric down-conversion, , as well as materials such as carbon nanotubes, and semiconductor quantum dots. , Among these methods, single photon sources based on semiconductor quantum dots are considered most promising due to their high brightness, , high purity, , and indistinguishability. − For example, InAs/InP quantum dots emit single photons in the telecom C-band spectrum, ,− which have been extracted utilizing various device structures, such as mesa structures, planar cavities, nanowires, and photonic crystal cavities . However, more efficient coupling to the optical fiber is needed to collect the telecom C-band single photon emission with high efficiency for long-distance quantum networks.…”