RESUMEN
Agile rf sources are a common requirement for control systems in quantum science and technology platforms. The direct digital synthesizer (DDS) often fills this role by allowing programmable control of the rf signals. Due to limitations of the DDS architecture, implementing an agile rf source requires rapid and precisely-timed programming of discrete updates that restrict the source's agility. Here, we describe a microcontroller-based interface that exploits the DDS's internal linear sweep accumulator to perform both sequential linear sweeps and standard discrete updates at the â¼10µs scale. This allows updates to the swept parameter as fast as every 8 ns with greatly reduced communication and memory overhead. We demonstrate the utility of this system by using it as the reference of an optical phase-locked loop to implement rapid, adjustable laser frequency sweeps in a Rydberg electromagnetically induced transparency spectroscopy measurement.
RESUMEN
High-power, narrow-linewidth light sources in the visible and UV spectra are in growing demand, particularly as quantum information and sensing research proliferates. Vertical external-cavity surface-emitting lasers (VECSELs) with intra-cavity frequency conversion are emerging as an attractive platform to fill these needs. Using such a device, we demonstrate 3.5 MHz full-width half-maximum Rydberg-state spectroscopy via electromagnetically induced transparency (EIT). The laser's 690 mW of output power at a wavelength of 475 nm enables large Rabi frequencies and strong signal-to-noise ratio in shorter measurement times. In addition, we characterize the frequency stability of the VECSEL using the delayed self-heterodyne technique and direct comparison with a commercial external-cavity diode laser (ECDL). We measure the pre-doubled light's Lorentzian linewidth to be 2π × 5.3(2) kHz, and the total linewidth to be 2π × 23(2) kHz. These measurements provide evidence that intra-cavity frequency-doubled VECSELs can perform precision spectroscopy at and below the MHz level, and are a promising tool for contemporary, and future, quantum technologies.
