All Polarization-Maintaining Fiber Wavelength-Tunable Ultrafast Visible Laser for Optically Detected Single-Electron Spin of Cerium Ion

We report a high-stability wavelength-tunable ultrafast visible laser source at 440-540 nm, which is useful for initializing and reading out a single-electron spin of cerium ion (Ce3+). The ultrafast visible laser source is seeded by an all polarization-maintaining (PM) fiber mode-locked laser at 1030 nm, with a repetition rate of 22.75 MHz and a relative intensity noise of only 0.0825% (integrated from 10 Hz to 200 kHz), and the pulse duration is measured to be 612 fs. After two stages of amplifier, the high-stability and low-noise Cherenkov radiation at 850 nm is generated in a PM photonic crystal fiber (PCF), and the wavelength tuning is implemented by leveraging sum frequency generation (SFG) and second-harmonic generation (SHG) in BaB2O4 (BBO). The output power of the ultrafast visible laser source is ∼2 mW with a root mean square error (RMSE) of 0.58% in one hour. In the optical detection of single-electron spin, the high-stability ultrafast laser source has an excellent excitation effect and a high rate of readout electron spin on samples of Ce3+.