Fig. 4: Electro-optic control of Er emission.

a Pulse sequence used to demonstrate control of Er emission. Pump: excitation laser pulse; gate: on/off control of SNSPD for fluorescence collection; EO voltage: voltage sent to the device for frequency tuning. In this sequence, fluorescence signal is collected while modulating the cavity frequency to suppress and enhance Er emission. b Measured results with pulse sequence in a. When electro-optic (EO) voltage is applied (green curve), a pulsed Er emission can be seen. The decay when cavity is on resonance corresponds well with the case without EO voltage (purple curve). c Pulse sequence for storage and retrieval of single ion excitation. After exciting a single ion, the cavity is detuned for a certain delay to store the excitation. The emission is then retrieved by tuning the cavity back on resonance. d Measured results with pulse sequence in c. The lifetime (T₁) of single Er ion is first probed to be 10 μs, shown by the red curve. The storage scheme is then applied with different tuning voltage. With 10 V (orange) and 80 V (blue), an extended lifetime of 172 μs and 2.82 ms is realized, respectively. e Fluorescence spectrum measured right after the pump pulse (purple curve) and after 100 μs delay in the storage scheme (green curve). The single ion emission peaks match well for two cases. The relative shift is potentially caused by system drift including laser instability and spectral diffusion. The red star mark indicates the peak used for measurement in c.