Resolving and resetting the charge environment of single T-centers in silicon p–i–n waveguides

The silicon T-center is a promising telecom-band spin-photon interface compatible with manufacturable silicon photonics. However, in nanophotonic devices, its optical linewidth is severely broadened by several gigahertz due to a fluctuating local charge environment, which limits photon indistinguishability for quantum networking. This paper investigates whether local charge-noise in lateral p-i-n waveguides can be characterized and suppressed to achieve unheralded optical linewidth narrowing and electrical tuning of single T-centers.

The authors integrate individual T-centers into the intrinsic region of lateral p-i-n waveguides fabricated on silicon-on-insulator (SOI) substrates and study them at a temperature of 15 mK. They implement two primary control mechanisms: a junction bias (applied via DC or arbitrary waveform generator pulses) to set a controllable electric field for Stark-shift tuning, and an above-band (640 nm) pulsed laser illumination to optically reset the charge environment by neutralizing local fields and filling traps. By combining photoluminescence excitation (PLE) measurements with above-band reset pulses (AB-PLE) and time-resolved sequences, the authors track spectral diffusion, field shifts, and the recovery dynamics of the charge environment.

Above-band illumination successfully neutralizes the steady-state local field and suppresses spectral diffusion, resulting in a dramatic 3.5-fold reduction in the median PLE linewidth down to 0.57 GHz across 46 tested emitters. An optimized emitter achieves an unheralded linewidth of 128 MHz, which supports coherent optical Rabi oscillations with a coherence time of 20 ns. The authors find that while DC bias produces a large Stark shift, it also broadens the line via a second-order Stark response. An analytical model confirms that the linewidth broadening under bias stems from a steepened local Stark slope acting on a fixed charge-noise distribution, whose root-mean-square width is evaluated to a median of 25.3 kV/m.