Photophysics of O-band and transition metal color centers in monolithic silicon for quantum communications

Abstract

Color centers in the O-band (1260-1360 nm) are critical for realizing long-coherence quantum network nodes in memory-assisted quantum communications. However, only a limited number of O-band color centers have been explored in silicon hosts as spin-photon interfaces. This study explores and compares two promising O-band defects in silicon: T centers and $^*$Cu (transition metal) color centers. During T center formation, we observed the formation and dissolution of various defects, including the copper-silver-related defect with a doublet line around 1312 nm ($^*$Cu$^{0}_{n}$), near the optical fiber zero dispersion wavelength. We then investigate the photophysics of both T and $^*$Cu centers, focusing on their emission spectra and spin properties to assess their potential for high-fidelity spin-photon interfaces. Additionally, we report a 25\% broadening of the $^*$Cu$^{0}_{0}$ line under a 0.5 T magnetic field, potentially linked to spin degeneracy, suggesting that this defect may provide a promising alternative to T centers for spin-photon interfaces.