Approaching transform-limited linewidths in telecom-wavelength transitions of ungated quantum dots

Abstract

Highly coherent quantum emitters operating in the telecommunication C-band (1530 - 1565nm), where ultra-low-loss fibers and photonic circuits are available, are crucial to the development of scalable quantum technologies. In this work, we report on a modified Stranski-Krastanov growth scheme using chemical beam epitaxy to enable the generation of high-quality InAs/InP quantum dots, characterized by near-transform-limited linewidths ($\hat{I}{“}_{\mathrm{TL}}$). We demonstrate the growth of highly-symmetric quantum dots with aspect ratios >0.8 and densities ranging from 2 to 22$\hat{I}¼$m${}^{-2}$. Optical characterization of these sources reveal fine-structure splittings down to $25\pm 4\hat{I}¼$eV and a single-photon purity of $g^{(2)}(0)=0.012\pm 0.007$, confirming the quality of these dots. Further, using an etalon to measure the linewidth, in combination with rigorous modelling, we find an upper-bound to the mean, low-power linewidths of only $12.1\pm 6.7\hat{I}{“}_{\mathrm{TL}}$ and, in the best case, $2.8\pm 1.8\hat{I}{“}_{\mathrm{TL}}$. These results represent a significant step in the development of telecom-wavelength quantum light sources which are essential for complex quantum networks and devices.