A 12.2 to 14.9 GHz injection-locked VCO array with an on-chip 50 MHz BW semi-digital PLL for transient spin manipulation and detection

We present an injection-locked 12.2 to 14.9 GHz VCO array with an on-chip large bandwidth semi-digital PLL for the real-time manipulation and detection of electron spins. With its large bandwidth of 50 MHz, the on-chip PLL allows for the precise control of the phase of the electron spins from an external reference. Moreover, we demonstrate experimentally that the spin signal can be measured with high sensitivity outside the PLL loop bandwidth by FM demodulation of the frequency-divided VCO output signal. The system was manufactured in 40nm bulk CMOS technology and its versatility and performance are verified in continuous-wave, rapid scan, and pulsed EPR experiments. In these experiments, it achieves a competitive spin sensitivity of $6 \times 10^{10}$ spins/$\surd {Hz}$ over a large sensitive volume of 180 nl. Moreover, the presented system, for the first time, allowed for the real-time inductive detection of Rabi oscillations as well as an intrinsically dead-time-free detection of free induction decays (FIDs) after an excitation pulse.